Cover Image
close this book Wells construction: hand dug and hand drilled
close this folder Appendices
View the document Appendix I: Conversion factors and tables
View the document Appendix II: Vegetation as an index of ground water
View the document Appendix III: Uses of dynamite in hand dug wells
View the document Appendix IV: Cement
View the document Appendix V: Leveling and plumbing the mold
View the document Appendix VI: Pipe
View the document Appendix VII: Pumps
View the document Appendix VIII: Water treatment in wells
View the document Appendix IX: Rope strength

Appendices

Appendix I: Conversion factors and tables

Length

Incn (in.) = 2.54 cm.

Foot (ft) = 12 in. = 30.48 cm

Yard (yd) = 3 ft = 0.9144 m

Mile = 5280 ft = 1.609 km

Centimeter (cm) = 0.3937 in. = 0.01 m

Meter (m) = 100 cm = 3.281 ft = 1.0936 yd

Kilometer (km) = 1000 m = 0.6214 mile

Area

Square inch (sq. in) = 6.452 cm²

Square foot (sq. ft) = 144 sq. in. = 929.0 cm²

Acre (43 560 sq. ft.) = 0.4047 ha

Square mile (sq. mile) = 640 acres = 2.590 km²

Square centimeter (cm²) = 0.155 sq. in

Square meter (m²) = 10 000 cm² = 10.764 sq. ft

Hectare (ha) = 10 000 m² = 2.471 acres

Square kilometer (km²) = 100 ha = 0.3861 sq. mile

Volume and Capacity

Cubic inch (cu. in.) = 16.387 cm³ or ml

Cubic foot (cu. ft) = 1729 cu. in. = 28.316 1 = 6.229 Imp.

gal = 7.481 US gal

Cubic yard (cu. yd) = 27 cu. ft = 0.7646 m³

Fluid ounce (British)(fl. oz.) = 28.41 ml

(US)(US fl. oz.) = 29.57 ml

Pint (British) (pt) = 20 fl. 02. = 0.5682 1

(US)(US pt) = 16 US fl. oz. = 0.4732 1

Quart (British) (qt) = 2 pt = 1.1365 1

(US)(US qt) = 2 US pt = 0.9463 1

Imperial gallon (British)(Imp. gal.) = 277.42 cu. in. = 1.20

US gal. = 4.546 1

US gallon (US gal.) = 231.0 cu. in. = 0.8327 Imp. gal = 3.785 1

Acre-foot = 1233.5 m³

Cubic centermeter (cm³) = 0.999972 ml = 0.06102 cu. in.

Mililiter (ml) = 1.000028 cm³ = 0.03520 fl. oz.

Liter (1) = 1000 ml = 0.2200 Imp. gal. = 0.2642 US gal.

= 0.035316 cu. ft

Cubic meter (m³) = 1000.028 1 = 1.3080 cu. yd = 220.0 Imp. gal

= 264.2 US gal = 0.0008107 acre-foot

 

Weight

Grain = 0.06480 g

Ounce (oz.) = 437.5 grains = 28.35 g

Pound (lb.) = 16 oz. = 0.45359 kg

Stone = 14 lb. = 6.350 kg

Hundredweight (cwt) (British) = 112 lb. = 50.802 kg

Hundredweight (cwt) (US) = 100 lb. = 45.359 kg

(Long) ton (British) = 2240 lb. = 1.01605 t

Short ton (US) = 2000 lb. = 0.90718 t

Gram (g) = 15.432 grains

Kilogram (kg) = 1000 g = 2.2046 lb.

Metric ton (t) = 1000 kg = 0.9842 long ton = 1.1023 short tons

ft³ water = 62.4 lbs.

1 liter water = 1 kg

 

Pressure

Pound per square inch (p.s.i.) = 0.06805 atm. = 0.07031 kg/cm²

= 0.7031 m of water = 2.307 ft of water

Standard atmosphere (atm.) = 14.696 p.s.i. = 1.0332 kg/cm²

Metric atmosphere kg/cm² = 14.223 p.s.i. = 0.9678 atm.

 

Flow rate

Cubic foot per second (cu. ft/sec) = 0.5382 mgd (Imp.) =

0.6463 msd (US)

Cubic foot per minute (cu.ft/min) = 0.4719 1/see

Imperial gallon per minute (Igpm) = 0.7577 1/see = 0.2728 m³/h

US gallon per minute (gpm) = 0.06309 1/see = 0.2271 m³/h

Million gallons per day (mgd) (Imperial) = 52.615 1/see

(US) = 43.811 1/see

Liter per second (1/sec) = 3.6001 m³/h = 13.20 Igpm = 15.85 gpm

= 0.019006 mgd (Imp.) = 0.022825 mgd (US)

Cubic meter per hour (m³/h) = 0.2778 1/see = 3.666 Igpm

= 4.403 gpm

 

Filtration rate

Million Imperial gallons per acre per day (mgad,Imp.) =

1.1234 m³/m²/day

Million US gallons per acre per day (mgad) = 0.9354 m³/m²/day

Cubic meter per square meter per day m³/m²/day

= 0.8902 mgad,

 

= 1.0691 mgad

 

Miscellaneous

Horsepower (h.p.) = 33 000 foot-pounds per minute = 0.746 kW

= 1.0139 CV

Kilowatt (kW) = 1.36 CV = 1.34 h.p.

Cheval-vapeur (CV) = 0.9863 h.p. = 0.736 kW

One liter of water weighs one kilogram (at 4°C)

One cubit foot of water weighs 63.43 pounds

One US gallon of water weighs a. 345 pounds

 

Appendix II: Vegetation as an index of ground water

The presence of certain species of vegetation can be a useful indication that ground water or soil moisture lies relatively close to the land surface. These plant indicators are most obvious in arid parts of the world, where green vegetation stands out, but the principle of using plant species as an index to locate ground water near the surface is equally useful in humid countries. The best relationships are found between certain groups of plants (called plant associations) and the depth of ground water or the salinity of water. In North Africa, for example, research has identified various plant associations (usually three to four main species per association) and their relationship to ground water depth and salt content of the water. The presence of certain trees and shrubs, for example the "salt cedar" type trees (Tamarix species), indicates salty water. Similarly, in the arid western U.S., Tamarix species, cottonwood trees, willows and other plants are associated with shallow ground water tables.

Plants whose roots actually tap the ground water are called "phreatophytes." Due to their high transpiration rates in arid zones, the phreatophytes can "pump out" a small stream or lower the level of a well. This transpiration loss could be of concern if, for example, many trees or other deep-rooted plants are planted around a well for shade or to stabilize sand in a dry, windy setting. High transpiration by the plants also can increase the salt concentration in the well water.

In arid zones, the perennial plants, especially trees and shrubs, are the most useful indicators of ground water. Annual plants, mainly legumes and grasses, are generally not good indicators since they come and go depending on rains and the season of the year.

Generally surveys of vegetation to help find shallow ground water are most effective if carried out in the dry season.

It would be useful at this point to present a table of plant species and plant associations, country by country. Unfortunately this information is not available for most countries, at least not in published form. Even if feasible, a list of all the plant species would be much too large. Finally, most people would need plant pictures and descriptions to accompany the names. You will therefore have to make the effort locally to determine the local plants which are good indicators of ground water, Sources of possible information include experienced well diggers or drillers in the area; water resource engineers; in rare cases, published reports (e.g., old FAO reports); and research station or university botanists. In many cases the necessary information can come only from interviews with these local sources of information.

 

Appendix III: Uses of dynamite in hand dug wells

This article by Christopher Henney was written as an overview of the uses of dynamite in the Peace Corp/Togo wells construction program.

It is reprinted from the Action/Peace Corps P&T Program and Training Journal (Special Issue: Wells Manual) published by the Peace Corps in 1974.

PART I: Obtaining ft

When to use dynamite

When and if you encounter a hard rock layer and there is NO OTHER WAY to break it in order to attain the aquifer, then dynamite Is in order. Of course, you could move the well site, but in some regions this probably would not make much difference. Never use dynamite before It is absolutely necessary as villagers will immediately start to rely on it as soon as the going gets rough. It is very difficult to stop using ft once you have started. Dynamite in an old well or using dig-a-meter-pour-a-meter method Start with small charges and deep blast holes and try to leave 50 cm between caissons and rock.

How to get ft

Because it is an extremely dangerous substance and can be used for sabotage or other crimes, most governments are very caution about whom they give permission to use dynamite; thus one's procedure for obtaining it should always be through all necessary officials channels. In Togo this generally means:

1) Chef-Cir

2) Travaux Publics or Assainissement

3) Interior Ministry

4) An authorized dealer

First you get your Chef-Cir to address a "demande de permission d'achat" permission to buy request to the Minister of Interior. This will state quantity and type of dynamite plus quantity and type of detonators. What purpose it is to be used for and where' where it will be kept, and by whom. Attached to this should be an agreement of your local boss; in my case the Engineer of Assainissement Sokode. This letter will then be transmitted to Lome (the capital) and will be returned as a letter of permission to the bureau of the Chef-Cir. He will give it to you. Remember this permission expires after six months, so use it immediately. With this letter you then go to Lome and order the dynamite and detonators from Brossette et Valor (an authorized dealer). This could take time as it must come from France. So plan 6 months ahead.

Another option is to have Travaux Publics-Service Hydraulique order it for you when they order theirs. Especially if you only want one or two cases. This is because Broesette requires a minimum order of three cases unless you want to wait until it can be attached to someone else's order. This also has the advantage of free transport up-country. It is not always easy to get a transporter to carry high explosives.

WHAT TO ORDER:

The Dynamite

There are a number of kinds of dynamite or explosives adaptable to wells. And the choice is probably bost made with expert help. Service Hydraulique is your best bet or Service des Mines. after wing three different types and talking to a number of people, I decided on the type known as "Comme A. Tolamite. This is a red gelatinous substance rolled into 50 grms. packages by means of wax paper. It is waterproof and maleable. The gases it releases upon ignition are non-toxic {although they may frritate lungs, but I will get to that later) and the stuff won't go off if bumped, smashed, dropped, etc. The maleability is important as sometime you want to squeeze it into a crack like toothpaste. I generally figure quantities on this scale:

1 charge - 50 or 100 grms. dynamite

Meters depth of rock

Diameter of well

Quantities

Number of blast holes

1 METER

1 meter ø

12 charges

3

1 METER

1 meter 25 ø

10 charges

5

1 METER

1 meter 40 ø

24 charges

6

1 METER

1 meter 80 ø

28 charges

7

This should be more than adequate; usually it takes two rounds of explosions to do a meter although this depends on the depth of the blast holes and the hardness of the rock. Normally your local water bureau or Travaux Publics will be able to tell you how deep you will have to blast. One case of dynamite weighs about 25-30 kg.

The Detonators

For each three charges, you will need two detonators. This will insure an adequate supply. Make sure they are electrical firing detonators. Fuses are dangerous and should not be used. The best kinds are type B66 low intensity, total resistance 1.5-3 ohms, medium 2 ohms. Make sure the wires are 2 m long.

In general both dynamite and detonators have an expiration date. So make sure you don't get an old batch, because it may be unstable and therefore DANGEROUS.

Where to Store and Now

The storage of dynamite is most important for your own health and that of others. Don't keen it at home as you may have kids or ocher curious people around. Personally, I prefer to keep ft at the local gendarmerie, police or travaux publics. This has a number of advantages:

a) You cannot be accused of sabotage for political reasons

b) If you work on weekends, you can get it at the first two places

c) If there is an accident, you are not around or responsible

Keep detonators away from dynamite,if possible at the other side of a locked room and in a case. Never let dynamite and detonators come into contact until you are ready to use them. Remember a good shock can set off the detonators, and detonators can blow your hand off. Keep tabs on how much you have and how much has been used. If you cannot keep it at the above mentioned locations, make sure you have a good store room with lock and the only key in your possesion.

How to Carry to your Site (If You Must)

If you don't want to keep it at the side because there is no adequate store room or you have many sites and prefer to bring it in when needed from a central store, then you must decide how it will be carried. I personally don't like this as there is a small amount of risk involved; but I did it for over six months. Anyway, if you follow certain simple rules, you should be all right.

1) Keep detonators and dynamite in separate waterproof sealed cans - The detonators preferably in a plastic one.

2) Keep the batteries or exploder somewhere else in your pack and separate from the detonators. This will insure you except if you get hit by lightning or squashed by a true*, both of which are very real dangers.

A normal crash because of sand, etc., should cause you no problems. (I had two).

PART II: Row to Use

Rules for Use in a Well

The use of dynamite follows a couple of rules of thumb:

a) Use common sense

b) Don't use more than needed to get the Job done

c) Make sure the site is cleared of people

d) Keep children away from site at all times

e) Get someone else to trigger ft

f) Don't let anyone else handle dynamite or detonators

g) Keep the batteries in your pocket or pack until you are out of the well and the site is cleared

h) Check whether all charges went off (see Part III)

i) Never send someone else to get dynamite or detonator. from the store room

j) Never go down in a well containing unfired charges unless you have secured the batteries

k) Place the charges yourself.

Rules a, b, c, d, g, j are constants, but e, f, i, k are changeable if you have trained a competent person to do the job. But no matter what happens, you will always be held responsible.

Tools You Need

Assuming you are working on a village level and you don't have a jack hammer (compressor), you will need:

1) Mining bar

2) 75 meters of extension cord flex

3) 1 roll of insulation tape

4) 1 flat file (to sharpen mining bar)

5) 5 flash light 1.5 volt cell batteries, size D

6) Dynamite and detonators

7) One 2-meter spoon

How to Place Charges

As I have said before, the number of charges is In proportion to the depth of the blast holes and the diameter or the well. A good rule of thumb is two charges per hole (blast hole) and:

3 holes for 1 m ø

5 holes for 1 m 25 cm ø

6 holes for 1 m 40 cm ø

7 holes for 1 m 80 cm ø

but depending on the rock, you may have three charges per hole (or one). Never blast if your holes are not deep enough. It is a waste of dynamite. The blast holes should be at least the length of a man's arm, 80 cm and preferably more. The deeper the better. Blast holes should always be in the most protruding places.


Figure A.


Here is a good diagram of where to place them in general

The charges toward the outside walls of the well should slope out as In Figure A and In the case of 4 - 1 charges.

How to Make up Charges

There are two methods thee I use: placing side by side, or one on top of the other.


Figure B.

I prefer the side by side method where the hole is large enough. This is done by unwrapping the wax paper around the dynamite and sticking the two charges together, then rewrapping. The detonator is then inserted until completely inside the dynamite. This method has the advantage of never having only one charge go off because the other got covered by mud and separated from the first charge as in the one on top of the other method. But in really hard rock it is sometimes not always possible to make the blast hole wide enough. The one on top method is also better for really deep holes as you can put 3-4 charges in with no difficulty. I might also mention that the tighter the fit of the dynamite, the better blast you are going to get. once the dynamite is in the hole with the detonator securely in the dynamite, pack the hole with damp sand. And pack the sand with a stick so it is well in and well packed.


Well packed hole

Don't pussy-foot but don't pound as if you were driving railroad spikes. This insures that the dynamite has some thing to push off on and that the gas does not escape out the open hole. Never till your hole up to the top with dynamite. This just is a noisy waste.

If you have more than one charge as you will most of the tame, you most hook them up in series. Each detonator has two wires, on one will be a flag.


Figure C. (a)

Now in order to hook up a series, you must hook flag to non flag of another charge:

This leaves you with one flag and one non flag which is than attached to the extension cord that goes above ground. Next collect your ends and tie them to the extension cord:


Figure C. (b)

If you have four detonators, there should be five joints left out of the *not, and so on. Make sure those are separated so as not to cause a short circuit.


Figure C. (c)

Also make sure that this knot is above the water level- -Preferably as high as possible without pulling the detonators out - and that is easier than imagined even when the charges are packed in sand. Than get out of your well, being careful not to pull on the extension cord.

How to Dig the Blast Roles

Using the blade end of the mining bar, pound the rock. This must be done while continually rotating the blade so as to make a nice neat round hole. At intervals, add water to make a slurry - this is messy but necessary. After a bit, use the 2 mater long spoon to get out the dust and dirt made from pulverized rock; or if the hole is wide enough, use your hand. Never make holes wider than your hand (fist) as this is Just wasteful of dynamite.

The sand will be blown out and little rock will be blasted. This is hard work and can take several days.

Ignition

To set off the dynamite, place the four or five batteries end to end and touch the two ends with the two ends of the cord. Make sure you do this firmly and keep the cord touching until you have counted five (oven though the explosions will happen spontaneously). This could save you many hours of looking for live charges that did not go off. For 1-3 charges, four batteries. Add one battery for every additional charge; i.e.

for 5 charges, 6 batteries; for 6 charges, 7 batteries, and

for 7 charges, 8 batteries.


Figure D.

Before you fire, clear the site. Let no one stand nearer than 50 meters to the well. Let a Togolese do the firing. There are two reasons for this. If someone gets hurt you did not pull the trigger, and Togolese-American relations will not be upset. Also, you are needed to keep a sharp look out for

falling rocks, impulsive children, or new arrivals. But if anything does happen, you will still be responsible for the sit. and though not legally, you will be held responsible in the eyes of. the people you are working with.

Once the explosion has gone off waft a minute. You will often be surprised how long ft takes rock to fall back to earth. Then pull up the extension cord and count the number of detonator wires. If all have gone off great, but if one is severed half way up, there is a chance it is still alive. Also, if there is anything holding the cord don't yank ft up. This could well be the wire that did not fiew, and by following it you will easily find the unfired charge instead of digging all over to find ft. Now waft 15 minutes half an hour until the smoke clears. You can choke to death by smoke inhalation even if the smoke is not toxio per se.

What to Do if a Charge does not go off

First, climb down and check your detonator wires. If one stays stuck, dig around it reasonably carefully. (If an explosion could not sat the charge off, you would really have to try). There is not too much danger if you are careful. When you reach sand, pull the detonator out slowly, then dig out the charge. The charge is now harmless. Or you can also rewire the detonator, climb out, and fire ft. If this does not work and you cannot extract the charge, put a net one In on top of it and fire that. This way your well is clean. Then sand workers down but Nor until you have at least extracted the detonator(s).

The causes of unfired charges are:

1) A short circuit

2) A sot of old batteries (no power)

3) Old detonators

After each explosion, chock out your cable and patch or cut. Then place batteries at one end and the two wires on your tongue at the other end' if ft tingles, all is well. Coil and put away. If not, find the short. Always do this after each explosion. It saves embarassmant when nothing goes off. You can work in up to 1 meter of water.

Recap of Procedure Rules

1) Only use dynamite where nothing else works.

2) Never use before it is absolutely needed, even when the work is hard.

3) Follow all official procedures in obtaining it.

4) Make sure It is not outdated stuff.

5) Never we fuses, always electric detonators.

6) Don't keep it at home, store safely.

7) Never send an inexperienced person to got it out of storage. Go yourself.

8) Keep dynamite separate from detonators and detonators separate from batteries.

9) Use commonsense (take all the risks that need taking yourself).

10) Don't use more than you have to.

11) Make sure the site is cleared of people.

12) Keep children away from site.

13) Get someone else to fire it while you watch.

14) Don't lot others handle dynamite or detonators or batteries.

15) When you are in well, keep batteries in your pocket. This is your only insurance.

16) After explosion, chock for unfired charges.

17) Never go after unfired charges unless you hero secured the batteries

18) Place all charges yourself.

19) Always pack some sand on top of a charge.

20) Make sure your detonators are wired properly and that the jointed ends don't touch.

21) Tie the wires to the cord.

22) Make sure knot is above water.

23) Don't pull on cord. You might extract detonators by accident.

24) Lot no one stand clover than 50 m when you blast.

25) Touch batteries firmly. Count to five.

26) Chock for dead charges yourself.

27) Wait for smoke to clear.

28) Check extension cable after each explosion.

29) Keep tools in good repair.

30) Remember you are responsible for your life and other lives.

PLEASE NOTE: Under no circumstance should dynamite be used unless an exhaustive study concernong its use has been conducted by experts who are knowledgeable In the use of dynamite.

GOOD LUCK AND TAKE CARE.

 

Appendix IV: Cement

A. Introduction to Cement

Cement is one of the most useful materials in wells construction. It can easily be mixed with sand and water to make mortar or with gravel, sand and water to make concrete. Both mortar and concrete are among the strongest and most durable materials used for all types of construction around the world. Mortar is normally used as the bonding agent between bricks or rocks while concrete is normally reinforced with steel bars and molded to the desired size and shape.

For well work, mortar or concrete is usually the best material for the lining, headwall, platform and cover of dug wells,and the platform and seal around the top three meters of casing in drilled wells.

Cement is available in almost every country in the world and sand and gravel are usually available locally. Occasionally it will be difficult to get cement for wells construction either because there are other higher priority demands for the cement or because it just costs too much. It is impossible here to say how or even whether cement can be obtained in such a circumstance.

Of the two cement compounds, mortar and concrete, concrete is the stronger. This is because the rock that makes up the gravel itself is stronger than the concrete and so contributes to its strength. Sometimes the two can be used interchangeably where lack of materials or working conditions demand it. Remember that concrete is the stronger product and should be used where possible.

NOTE: The rest of the discussion in this appendix will deal specifically with concrete. The same procedures can and should be followed if mortar is used instead.

B. Ingredients of Concrete

Concrete is made from cement, sand, gravel and water. These ingredients are combined in certain proportions to achieve the desired strength. The amount of water used to mix these ingredients is by far the most important factor in determining the final strength of the concrete. Use the least amount of water that will still give you a workable mix. Sand and gravel, which are sometimes referred to as fine and coarse aggregate respectively, should be clean and properly graded. Cement and water form a paste which, when mixed, acts as a glue to bind the aggregates together in a strong hard mass.

1. Proportions:

• There are four major ingredients in concrete: cement, sand, gravel, water.

• Dry ingredients are normally mixed in certain proportions and then water is added. Proportions are expressed as follows: 1:2:4, which means that to one part cement you add two parts sand and four parts gravel. A "part" usually refers to a unit of volume. Example: A 1:2:4 concrete mix could be obtained by mixing 1 bucket full of cement with 2 buckets of sand and 4 buckets of gravel.

• Proportions are almost always expressed as cement: sand:gravel, and they are usually labelled that way.

• There are many minor variations in the proportions used for mixing concrete. The most commonly used are 1:2:4, 1:2:3, 1:2.5:5. For our purposes all work equally well.

NOTE: A 1:2:4 mix will go a little farther than the 1:2:3 mix and allows a little more room for using not the best sand or gravel than a 1:2.5:5 mix.

• Normal range for amount of water used to mix each 50 kg bag of cement is between 20 liters and 30 liters (94 lb. bag of cement is between 4.5 gal. and 7 gal.)

• The water-tightness of concrete depends primarily on the water-cement ratio and the length of moist curing. This is similar to concrete strength in that less water and longer moist curing promote watertightness.

2. Choice of ingredients

• cement: The descriptions and properties given here are specifically of Portland cement. This is the type most commonly used and what we think of when we say cement.

When used, it should be dry, powdery and free of lumps. When storing cement try to avoid all possible contact with moisture. Store it away from exterior walls, off damp floors, and stacked close together to reduce air circulation. If it could be kept completely dry it could be stored indefinately. Even exposed to air it will gradually draw moisture, thus limiting even the covered storage time to between 6 months and 1 year depending on conditions.

• water: In general, water fit for drinking is suitable for mixing concrete. Impurities in the water may affect concrete, setting time, strength, shrinkage or promote corrosion of reinforcement.

• aggregates: Fine and coarse aggregates together occupy 60 to 80% of concrete volume.

- fine aggregate: Sand should range in size from less than .25 mm to 6.3 mm. Sand from sea shores, dunes or river banks is usually too fine for normal mixes. (You can sometimes scrape about 30 cm of fine surface sand off and find coarser, more suitable sand beneath it.)

- large aggregate: Within the recommended size limits mentioned later, the larger the gravel you use the stronger and more economical the concrete will be.

• The larger the size of the gravel the less water and cement will be required to get the same strength concrete.

• The maximum gravel size should not exceed

- one-fifth the minimum dimension of the member;

- three-fourths the clear space between reinforcing bars or between reinforcement and forms. (Optimum aggregate size in many situations is about 2.0 cm.)

The shape and surface texture of aggregates affect properties of freshly mixed concrete more than they affect hardened concrete. Rough textured or flat and elongated particles require more water to produce workable concrete than do rounded or cubical aggregates and more water reduces the final strength of the concrete.

It is extremely important to have the gravel and sand clean. Silt, clay, or bits of organic matter in even low concentrations will ruin concrete. A very simple test for cleanliness makes use of a clear wide-mouth jar. Fill the jar about half full of the sand and small aggregate to be tested, and cover with water. Shake the mixture vigorously, and then allow it to stand for three hours. In almost every case there will be a distinct line dividing the fine sand suitable for concrete and that which is too fine. If the very fine material amounts to more than 10% of the suitable material, then the concrete made from it will be weak.

This means that other fine material should be sought, or the available material should be washed to remove the material that is too fine. This can be done by putting the sand (and gravel if necessary) in some container such as a drum. Cover the aggregate with water, stir thoroughly, and let stand for a minute, and pour off the liquid. One or two such treatments will remove most of the very fine material and organic matter.

Another point to consider in the selection of aggre-gate is its strength. About the only simple test is to break some of the stones with a hammer. If the effort required to break the majority of aggregate stones is greater than the effort required to break a similar sized piece of concrete, then the aggregate will make strong concrete. If the stone breaks easily, then you can expect that the concrete made of these stones will only be as strong as the stones themselves.

In very dry climates several precautions must be taken. If the sand is perfectly dry, it packs into a smaller space. If you put 20 buckets of bone dry sand in a pile and stirred in two buckets of water, you could carry away about 27 buckets of damp sand. If your sand is completely dry, add some water to it or else measure by weight instead of volume. The surface of the curing concrete should be kept damp. This is because water evaporating from the surface will remove some of the water needed to make it cure properly. Cover the concrete with building paper, burlap, straw, or anything that will hold moisture and keep the direct sun and wind from the concrete surface. Keep the concrete moist by sprinkling as often as necessary; this may be as often as three times per day. After the first week of curing, it is not necessary to keep the surface damp continuously. (See p. 236.)

3. Making Quick-Setting Concrete

To produce quick-setting concrete with high initial strength, calcium chloride can be added to the mixture.

This will not affect the estimation of materials needed because the calcium chloride will be dissolved in the water used to mix the concrete.

Quick-setting cement is often useful for example, when repeated castings are needed from the same mold. A concrete mixture which contains calcium chloride as an accelerator will set about twice as fast as a mixture which does not. The mixed batch must be put into the forms faster, but since quick-setting batches are usually small, this is not a problem. Calcium chloride does not lessen the strength of fully-cured concrete.

No more than 1 kg (2 pounds) of calcium chloride should be used per sack of cement. It should be used only if it is in its original containers, which should be moisture-proof bags or sacks or air-tight steel drums.

The best way to add the calcium chloride is to mix up a solution containing 1/2kg per liter (1 pound per quart) of water. Use this solution as part of the mixing water at a ratio of 2 liters (2 quarts) per sack of cement.

4. Estimating quantities of materials needed

1. Calculate the volume of concrete needed.

2. Multiply the volume of concrete needed by 3/2 (1.5) to get the total volume of dry loose material needed. The cement and sand do little to add to the volume of the concrete because they fill in the air spaces between the gravel.

3. Add 10% (1/10) for losses due to handling.

4. Add the numbers in the volumetric proportion that you will use to get a relative total. This will allow you later to compute fractions of the total needed for each ingredient. (1:2:3=6)

5, Determine the amount of cement needed by multiplying the volume of dry material needed (from step 2) by the proportional amount of the total mix (amount cement needed) = 1/6 x (volume dry materials).

6. Divide by the unit volume per bag, 33.2 liters per 50 kg bag cement or 1 cubic foot per 94 lb. bag cement. When figuring the number of cement bags round up to nearest whole number.

NOTE: This calculation, even with the 10% addition for handling losses, rarely leaves any extra concrete, particularly for small jobs requiring less than 5 hand mixed bags of cement.

Here is an example:

• the volume of a cylinder = Pr2h =(3.1416)(radius)2(height)=(3.1416)(radius)(radius)(height)

• the volume of concrete needed to build the lining and platform of the pictured well could be computed as follows (See Fig. IV-1).

- the volume of the lining and headwall would be the volume of the 20.8m high cylinder with a 0.7m radius minus the volume of the 20.8m high cylinder with a 0.6m radius.

- V = [P(.7)2(20.8)-[ P(.6)2(20.8)]

= [(3.1416)(.49)(20.8)] - [(3.1416)(.36)(20.8)]

= 32.0-23.5

= 8.5m3


FIG. IV-1. CROSS SECTION OF TYPICAL WELL FOR CALCULATION OF CONCRETE NEEDS

- the volume of the platform would be the volume of the .08m high cylinder with a 2m radius minus the volume of the .08m high cylinder with a .7m radius.

- V = [(3.1416)(2)2(.08)] - [(3.1416)(.7)2(.08)]

[(3.1416)(4)(.08)] - [(3.1416)(.49)(.08)]

= 1 - 0.1 = 0.9 m3

Following the steps outlined above the volume of materials necessary to construct the well would be computed as follows:

1. total volume = 8.5 + .9 = 9.4 m³

2. (9.4)(1.5) = 14.1 m³ dry material estimated

3. 14.1 x 1.1 = 15.5 m³ dry material necessary because of losses in transport.

4. 1:2:4 cement:sand:gravel 1+2+4=7

5. 15.5 x 1/7 = 2.2 m³ cement

15.5 x 2/7 = 4.4 m³ sand

15.5 x 4.7 = 8.9 m³ gravel

6. 2.2 m³ cement = 2,200 liters (1.) of cement

2,200 1. cement 33.2 1. per 50 kg bag cement = 66.26 bags of cement

67 bags of cement will be needed.

C. Construction with Concrete

1. Outline of Concrete Work

• build form;

• place rerod;

• mix concrete;

• pour concrete;

• finish surface;

• cure concrete;

• remove forms.

2. Interior Well Forms

a. Introduction

An interior well form or mold is circular with a smooth exterior surface which will form the inside surface of the lining. This form can be used either on the surface with other forms to make lining rings or in the well to form a lining that is poured in place. (See Fig. IV-2.)


FIG. IV-2. INTERIOR LINING FORM

Freshly mixed concrete is heavy and plastic. Forms for holding it in place until it hardens must be well braced and should have a smooth inside surface. Cracks, knots, or other imperfections in the forms may be permanently reproduced in the concrete surface.

Forms should be easy to fill with concrete and easy to remove once the concrete has hardened. Be sure that the fasteners used to hold the form together are both accessible and easy to unfasten.

NOTE: When using nails to hold a wood form together, do not drive them all the way in. Leave them sticking up just enough so that they can easily be pulled when necessary to remove the form.

b. Materials for Forms

The following materials are used to construct interior forms:

• steel: forms made of steel range in height from 1/2 m to 1 m. They are heavy, awkward, and expensive but last for a long time.

• sheet metal: with a simple triangular interior support, forms made of sheet metal have proved to be successful. They are lighter and more maneuverable than steel forms but are not as strong and durable.

• wood: this material is commonly used because it is lightweight and strong. It must be carefully bent, waterproofed, and reinforced.

By using boards as wide as possible, form construction will be easier and quicker. It will also reduce the number of lines on the concrete surface that form at the junction of two boards. Plywood is excellent, especially if it has a special high density overlay surface. This allows for a smoother concrete finish, easier form removal and less wear on the forms.

If unsurfaced wood is used for forms, oil or grease the inside surface to make removal of the forms easier and to prevent the wood from drawing too much water from the concrete. Do not oil or grease the wood if the concrete surface will be painted or stuccoed.

• earth: Any earth that can be dug into and still hold its shape can also be used as a form. Carefully dig out the desired shape and fill it with concrete. Once the concrete has set and cured it can be dug up and used where needed. A new form will have to be dug out for each piece of concrete poured. (See Figs. 8-12 and 9-10.)

• other materials: Plastics and fiberglass are a so occasionally used and continue to be experimented with as form materials. Fiberglass is much lighter than steel and, if taken proper care of, should last for a long time. Its cost and availability in developing nations seem to be the only factors limiting more widespread trials.

3. Concrete Reinforcement

Reinforcing concrete will allow much greater loads to be carried. Design of reinforced concrete structures that are large or must carry high loads can become too complicated for a person without special training.

Concrete alone has great compression strength but little tension strength. Concrete is very difficult to squeeze (compression), but breaks relatively easily when stretched (put in tension). Reinforcing steel has exactly the opposite properties; it is strong in tension and weak in compression. Combining the two results in a material (reinforced concrete) which is strong in both compression and tension and therefore useful in a large number of situations.

Concrete is best reinforced with specially made steel rods which can be imbedded in the concrete. Bamboo has also been used to reinforce concrete with some success although it is liable to deteriorate in time.

• Reinforced concrete sections should be at least 7.5 cm thick and 10 cm is much better.

• The reinforcing rod (rerod) usually comes in long sections of a given diameter.

• The range of different diameter sizes commonly manufactured is usually measured in millimeters; for example, 4 mm, 6 mm, 8 mm, 10 mm, and 12 mm.

• Exactly how much rerod is needed in a particular pour will depend on the load it will have to support. For most concrete work, including everything discussed in this manual, rerod should take up 0.5% to 1% of the cross-sectional area.

• Reinforcing rods should also have clean surfaces free of loose scale and rust. Rods in poor condition should be brushed thoroughly with a stiff wire brush.

• When placing rerod in a form before the concrete is poured it should be located:

- at least 2.5 cm from the form everywhere.

- in a plane approximately two-thirds of the way into the thickness of the pour from the side which will have a weight or force pressing on the concrete. (See Fig. IV-3.)


FIG. IV-3. REINFORCING ROD PLACEMENT (ALSO SEE FIGS. 8-3 AND 8-5 FOR REROD PLACEMENT IN LINING)

- in a grid so that there is never more than 3 times the final concrete thickness between adjacent rods.

- no closer than 3 cm to a parallel rod.

• Rerod strength is approximately additive according to cross-sectional area. Four 4 mm rods will be about as strong as one 8 mm rod. The crosssectional area of four 4 mm rods equals the crosssectional area of one 8 mm rod.

• The rod should be arranged in an evenly spaced grid-type pattern with more and/or thicker rod along the longest dimension of the pour.

• All intersections where rods cross should be tied with thin wire.

• When tying one rod on to another to increase the length of the rods, they should overlap 20 times the diameter of the rod and be tied twice with wire. (See Fig. IV-4.)

Rod size

Overlap

6 mm

12 cm = 120 mm

8 mm

16 cm = 160

10 mm

20 cm = 200

12 mm

24 cm = 240


FIG. IV-4. REROD OVERLAP

• Larger sizes of rod often have raised patterns on them which are designed to allow them to be held firmly in place by the concrete. Smaller sizes of rod are generally smooth. When using smooth rod always make a small hook at the end of each piece that will be in the concrete. Without the hook, temperature changes may eventually loosen the concrete from the rod thereby losing much of its reinforcing effect.

• Rerod should be carefully prepared so that the rod is straight and square where it should be. Sloppy rod work will result in weaker concrete and wastes rod.

• For particularly strong pieces or where small irregular shapes are being formed, the rerod can be put together in a cage-like arrangement. Use small rod for the cross-sections and larger rod for the length. This system is used to reinforce pieces like a cutting ring, with its irregular shape, or perhaps a well cover,which may have many people standing on it at one time.

• Where possible, it is usually best to assemble rerod inside the form so that it will fit exactly.

• The proper distance from the bottom of the pour in a slab can be achieved by setting the rod on a few small stones before the concrete is poured or simply pulling the rerod grid a couple of centimeters up into the concrete after some concrete has been spread over the whole pour.

4. Mixing Concrete BY Machine or By Hand

a. Mixing by Machine

Concrete must be thoroughly mixed to yield the strongest product. For machine mix, allow 5 or 6 minutes after all the materials are in the drum. First, put about 10% of the mixing water in the drum. Then add water uniformly with the dry _ materials, leaving another 10% to be added after the dry materials are in the drum.

b. Mixing by Hand

On many self-help projects, the amount of concrete needed may be small or it may be difficult to get a mechanical mixer. Concrete can be mixed by hand; if a few precautions are taken, it can be as strong as concrete mixed in a machine.

The first requirement for mixing by hand is a mixing area which is both clean and watertight. This can be a wood and metal mixing trough (Fig. IV-5) or a simple round concrete floor (Fig. IV-6).


FIG. IV-5. MIXING TROUGH


FIG. IV-6. MIXING PLATFORM

Use the following procedure:

1) Spread the fine aggregate evenly over the mixing area.

2) Spread the cement evenly over the fine aggregate and mix these materials by turning them with a shovel until the color is uniform.

3) Spread this mixture out evenly and spread the coarse aggregate on it and mix thoroughly again. All dry materials should be thoroughly mixed before water is added.

When work is finished for the day, be sure to rinse concrete from the mixing area and the tools to keep them from rusting and to prevent cement from caking on them. Smooth shiny tools and mixing boat surfaces make mixing surprisingly easier. The tools will also last much longer. Try to keep from getting wet concrete on your skin because it is caustic.

A workable mix should be smooth and plastic -neither so wet that it will run nor so stiff that it will crumble.

If the mix is too wet, add small amounts of sand and gravel, in the proper proportion, until the mix is workable.

If the mix is too stiff, add small amounts of water and cement, maintaining the proper water-cement ratio, until the mix is workable.

Note the amounts of materials added so that you will have the correct proportions for subsequent batches.

If a concrete mix is too stiff, it will be difficult to place in the forms. If it is not stiff enough, the mix probably does not have enough aggregate, thus making it an uneconomical use of cement.

5. Pouring Concrete into Form

To make strong concrete structures, it is important to place fresh concrete in the forms correctly.

The wet concrete mix should not be handled roughly when it is being carried and put in the forms. It is very easy, through joggling or throwing, to separate the fine aggregate from the coarse aggregate. Do not let the concrete drop freely for a distance greater than 90 to 120 cm. Concrete is strongest when the various sizes of aggregates and cement paste are well mixed.

Properly proportioned concrete will have to be worked into place in the form. Concrete that would on its own flow out to completely fill in a form would be too wet and therefore weak.

When pouring concrete structures that are over 120cm high, leave holes in the forms at intervals of less than 120cm through which concrete can be poured and which can later be covered to permit pouring above that level. Alternatively, a slide could be used through which concrete could flow down to the bottom of the form without separating.

Any "u"-shaped trough wide enough to facilitate pouring concrete into it, narrow enough to fit inside the form, and long enough so that the concrete can slide down the chute without separating will work.

As the concrete is being placed it should be compacted so that no air holes, which would leave weak spots in the concrete, are left. This can be done by tamping the concrete with some long thin tool or vibrating the concrete in one of several ways. Tamping can be accomplished with a thin (2 cm) iron rod, a wooden pole or a shovel.

On large commercial jobs concrete is compacted with a special vibrator usually powered by an air compressor which is submerged in the concrete immediately after it is poured. The concrete will be compacted to some extent as it is moved into its final position in the form. However, special attention must be paid to the edges of the pour to make sure that the concrete has completely filled in the form up to the edges. If the forms are strong enough they can be struck with a hammer on the outside to vibrate the concrete just enough to allow it to settle completely in against the forms. Too much tamping can force most of the large aggregate toward the bottom of the pour, thus reducing the overall strength of the concrete.

6. Finishing

Once the concrete is poured into the forms, its surface should be worked to an even finish. The smoothness of the finish will depend on what the surface will be used for. Where more concrete or mortar will later be placed on this pour, the area should be left relatively rough to facilitate bonding. Where the surface will later be walked on, as for example the cover of a well on which a pump will be mounted, it should be somewhat rough to prevent people from slipping on the concrete when its surface is wet. This somewhat rough texture can be achieved by finishing with a wooden float or by also lightly brushing the surface to give it a texture. A very smooth finish can be made with a metal trowel. Overfinishing (repeated finishing) can lead to powdering and erosion of the surface.

7. Curing Concrete

After the forms are filled, the concrete must be cured until it reaches the required strength. Curing involves keeping the concrete damp so that the chemical reaction that causes the concrete to harden will continue for as long as is necessary to achieve the desired strength. Once the concrete is allowed to dry the chemical hardening action will gradually taper off and cease.

The early stage of curing is extremely critical. Special steps should be taken to keep the concrete wet. Once the concrete dries it will stop hardening; after this happens it cannot be re-wetted in the field to re-start the hardening process.

Covering the exposed concrete surfaces is usually easier than continuously sprinkling or frequently dousing the concrete with water which would otherwise be necessary to prevent the concrete surface from becoming dry to the touch. Protective covers often used include canvas, empty cement bags, burlap, plastic, palm leaves, straw and wet sand. The covering should also be kept wet so that it will not absorb water from the concrete.

Concrete is strong enough for light loads after 7 days. In most cases, forms can be removed from standing structures like bridges and walls after 4 or 5 days, but if they are left in place they will help to keep the concrete from drying out. Where concrete structures are being cast on the ground, the forms can be removed as soon as the concrete sets enough to hold its own shape (3 to 6 hours) if there is no load on the structure and measures are taken to ensure proper curing.

The concrete's final strength will result in part from how long it is moist cured. As can be seen from the graph, concrete will eventually reach about 60% of its design strength if not moist cured at all, 80% if moist cured for 3 days, and almost 100% if moist cured for 7 days. If concrete is kept moist it will continue to harden indefinitely.

You will also notice from the graph that even though the concrete may be cured for 7 days, at that point it will only have gained about 60% of the strength it will ultimately have and that it will be another 3 weeks before it reaches 90% of its ultimate strength. Practically,this means that when pouring a concrete ring which will later be put in the well even after curing has stopped, the ring should be left alone for at least another week (and preferably longer) before it is installed in the well. It will during that time harden to reach about 75% of its final strength.


GRAPH: STRENGTH OF CONCRETE AFTER DAYS OF MOIST-CURING

 

Appendix V: Leveling and plumbing the mold

When you check the level of the mold you also take a measure of whether or not the sides of the mold are perfectly plumb. If they are perfectly plumb the shaft will go straight down. A well does not have to have a shaft that goes straight down; it could just as easily curve or go down at an angle. Plumb is easy to measure, however, and there are many reasons why it is desirable to keep the well plumb.

1) A plumb well shaft and lining is a stronger structure than one that is not plumb.

2) Sinking the hole straight down requires less excavation work than an angled or a curved hole.

3) Fewer materials are required to construct a lining that will support the well.

4) If a pump is to be installed, the pipe that reaches to water should be perfectly plumb. If it is not plumb, there will be greater stress on the pipe and pumping components will wear out much sooner than they should.

1. Tools

Use a commercial level (see Fig. V-3 ) or a clear plastic hose with water in it. (See Fig. V-4.)

For the purpose of demonstration, level the interior lining mold in the well with a commercial level (spirit level, or water level). The normal ordinary level has a clear glass or plastic tube which is slightly curved and full of liquid with one air bubble; there will also be two marks on the tube, one on either side of the center of the tube. To read the level set it, with the tube side up, on whatever you want to check; the object will be level when the air bubble in the tube is exactly centered between the two marks on the tube. (See Fig. V-1.)


FIG. V-1. BUBBLE BETWEEM TWO MARKS INDICATING LEVEL OBJECT

If the object is not level the bubble will be off-center toward the side which is highest. (See Fig. V-2.)


FIG. V-2. BUBBLE ON HIGHER SIDE OF UN-LEVEL OBJECT

2. Care of the level

Levels are sensitive and exact instruments which arrive adjusted from the factory. Great care should be taken never to drop a level or otherwise damage its edges. Many levels also come with insets for checking verticality (plumb) and 45° angles, (See Fig. V-3.)


FIG. V-3. COMMERCIALLY MANUFACTURED LEVEL

If a level is not commercially available, you can easily make your own level with a clear plastic hose and water. (See Fig. V-4.)


FIG. V-4. CLEAR HOSE AND WATER USED AS LEVEL

If the surface of the water in the hose is even with the edge of the mold on one side, then when the edge of mold on the opposite side of the hole is even with the surface of the water in the other end of the hose, the mold is level in that direction.

Water in two ends of the same tube will always be at the same height no matter what the tube does between the two ends.

NOTE: If the diameter of the clear plastic hose is small, a "meniscus" (U-shaped surface due to capillary action) may form. All level readings should be made at the same point of the meniscus, preferably at the center.

3. Checking the level of a horizontal object

Always check the level in two opposite directions before declaring that an object is level.

For a flat plate, see Fig. V-5.


FIG. V-5. LEVEL CHECKED IN TWO DIRECTIONS ON FLAT SURFACE

For a lining mold, see Fig. V-6.


FIG. V-6. LEVEL CHECKED IN TWO DIRECTIONS ON LINING MOLD

To check two objects not connected with each other, find a straight object (a board, a shaft etc.) that can be laid down between the two objects to be laid two objects to be leveled. (See Fig. V-7.)


FIG. V-7. USING A STRAIGHT BOARD TO CHECK LEVEL ACROSS MOLD

Check the straightness of the board by looking along its edges from one end.

 

Appendix VI: Pipe

A. Introduction

Water is often needed in locations where none is available. Pipe can help to meet this need if there is some force available to move water through it. Gravity and pumps can exert the necessary force on water to cause it to flow through a pipe. But pipe can be expensive and may not be appropriate for use in some situations. Where water needs to be transported from one place to another across the surface of the earth, a simple trough arrangement might work and be more easily repaired when damaged.

Generally speaking, however, pipe is superior to other water transportation devices. It is readily available and it can be used for a number of purposes, besides transporting water. It is commonly used in the casing for drilled wells and in the drop pipe for pumps. Depending on the material from which it was made, it can be used to make many handy tools or simple equipment.

NOTE: For pipes laid in the ground, always maintain sufficient pressure in a completed line of pipe so that water will leak out of any holes. If pressure around the pipe is greater than that inside it, contaminants from the ground will be forced into the pipe.

When evaluating possible pipe choices, a number of factors should be considered. They include:

• cost;

• accessibility/availability;

• pressure. Where necessary, can the pipe withstand the pressure of the water that will be carried inside it? Computing the actual pressure is beyond the scope of this manual.

It is sufficient to say here that the pressure of the water is directly related to the vertical height of the water column above that point.

• pipe connections. Can the pipe connections be made completely watertight, to prevent unnecessary loss of water and the entrance of possible contaminants?

• weight. Will you need special equipment to raise or lower the needed length of pipe?

• possibility of decay or corrosion. Is the pipe suitable for the ground and water conditions in which you intend to use it?

B. Pipe Materials

1. Bamboo

Although an appealing idea considering the widespread availability of bamboo, in fact bamboo is seldom used as water pipe. This is due to the fact that it is essentially a temporary solution, requiring considerable upkeep to keep a well from being contaminated by the rotting of the bamboo segments.

• Bamboo can take the pressure from a column of water 20m in height, or about 2 atmospheres.

• Preserve bamboo for use as water pipe with oil based paint or varnish to seal it on the outside, or soak in 5% boric acid and water solution.

NOTE: Boric acid can give water an unpleasant smell for about three weeks.

• Chisel or drill to break inner membranes of bamboo.

• Join pieces by three possible methods:

1) sliding one piece into the next, and then wrapping the joint with tar-soaked rope;

2) using extra bamboo as interior or exterior coupling and then wrapping the joint with tar-soaked rope;

3) wrapping cow-hide tightly twice around the joint and sealing it with two pieces of wire.

• There will be a three to four year life expectancy if the pipe is carefully installed.

• If chlorine is used to disinfect the water before it flows through the pipe, allow sufficient contact time for chlorine to act before the water enters the pipe.

2. Iron or Steel-commonly referred to as "black" pipe

• Iron or steel is frequently used for water pipe even though it is sometimes subject to rust and corrosion from the water.

• These materials are commonly used as casing pipe for drilled wells where the water is not corrosive.

• Iron and steel are galvanized to help prevent rust and corrosion. (See next entry.)

3. Galvanized Iron or Galvanized Steel

• Regular iron or steel pipe is simply coated with a thin layer of zinc when galvanized. This helps reduce rust and corrosion normal to iron and steel.

• The piping is joined by threaded connections. The threading process cuts through the zinc layer. Thus, threads are particularly susceptible to rusting and corrosion.

• Galvanized iron or steel is commonly manufactured in metric and English sizes.

• Because this material is strong, the pipe is also particularly useful in manufacturing many small tools and pieces of equipment to suit a specific job and location.

4. Plastic - ABS (Acrylonitrile-Butadiene-Styrene)

• ABS plastic has excellent impact resistance, even at low temperatures.

• ABS has heat resistance up to 160°F.

• It has pressure ratings of 1,000, 1,250 and 1,600 pounds per square inch (p.s.i.), depending on composition and thickness.

• It possesses excellent corrosion and chemical resistance to non-oxidizing chemicals.

• It can be joined by solvent cementing or by pipe threads where wall thickness is adequate.

ABS plastic also presents certain problems:

• It is subject to attack from organic solvents.

• Direct exposure to the ultraviolet rays of the sun reduces its strength and elongation properties. This is a gradual process which is likely to significantly affect the pipe strength only after months of exposure.

Plastic - PE (Polyethylene)

• There are three types of plastics, varying from soft to hard. Their rigidity, tensile strength, surface hardness, softening temperature and chemical resistance increase with density and molecular weight.

• They have p.s.i. ratings of 80, 100, 125, and 160, according to composition and thickness.

• They are extremely resistant to chemicals.

• This kind of plastic can be joined by flaring, using insert fittings, or by heat fusion.

• They are low cost, lightweight and flexible, long lengths can be coiled.

PE plastic also presents certain problems:

• It has low design stress and poor rigidity.

• The temperature limit varies from 100 to 180°E depending on density.

• PE plastic is sensitive to light but can be left in the open for a month or more

• It is flammable, although easily extinguished.

• American and European polyethylenes have different density ratings.

Plastic - PVC (Polyvinyl Chloride)

• PVC plastic has excellent strength and rigidity.

• Its p.s.i. ratings are comparable to those or PE and ABS.

• It is extremely resistant to chemicals and oils.

• It can be joined by heat fusion, by solvent cement, or by various kinds of mechanical joints.

• It is readily threaded if there is sufficient wall thickness.

PVC plastic also presents certain problems:

• It is readily softened by ether, ketones and chlorinated hydrocarbons.

• It is heavier than PE and ABS.

• Its temperature limit is 150°F.

• However, its many advantages make it widely used as plastic pipe.

5. Concrete

• Concrete is usually used to make large culverttype pipe.

• It can be used as well casing or lining if care is taken to seal successive sections from each other.

6. Fired Clay

• Clay is usually used to make four inch to six inch drainage tile.

• Unless it is manufactured with special end fittings, usually a bell and socket, it is not easily adapted to water transport.

• It is relatively weak and easily broken.

 

Appendix VII: Pumps

A. Introduction

There are many different kinds of pumps in use around the world. This discussion is limited to an overview of the most commonly used pumps.


FIG. VII-1. PUMP ACTION

(a) As the piston goes down, the check valve in it opens allowing the water to come through. The check valve at the base of the cylinder remains closed holding the water in the cylinder.

(b) As the piston moves up, the check valve in it closes allowing the water above the piston to be lifted. The rising piston also pulls more water up into the cylinder through the valve at its base.

(c) and (d) The continued down and up motion of the piston inside the cylinder and the opening and closing of the different valves enables water to be moved up and out or the pump.

The most common type of hand pump uses a smooth cylinder against which a piston (plunger) slides up and down. The up and down motion of the piston, coupled with the concurrent action of two valves, causes water to move through the cylinder. (,See Fig. VII-1.)

While there are other types of pumping mechanisms which will be mentioned later, this type of pump is by far the most common.

B. Piston Pump Variations

1. Shallow/deep well pumps

Although the basic operation of cylinder pumps is always the same, there are two different arrangements of the components depending on the distance between the pump and the water surface. For the pump to work the cylinder must be within 6.5 m of the water surface in the well.

Shallow well pump: If the water level in the well is within 6.5 m of where the bottom of where the pump will be placed, the cylinder can be incorporated into the pump body. (See Fig. VII-2.)

Deep well pump: If the water level in the well is more than 6.5 m from the bottom of the pump at any time, the cylinder will have to be inside the well. (See Fig. VII-3.)

Because the working parts of the pump are all above ground in the shallow well pump, this pump is much easier to repair. Deep well pumps, however, are more common because water is not often found within 6.5 m of the ground surface.


FIG. VII-2. SHALLOW WELL LIFT PUMP


FIG. VII-3. DEEP WELL LIFT PUMP

NOTE: Contrary to popular opinion, pumps do not 'lift' water up from the source. Instead, the pump reduces the atmospheric pressure on the water in the suction pipe and the atmospheric pressure on the water outside of the suction pipe pushes the water up and into the pump. The principle is the same as that of drawing water through a straw or filling a syringe.

Theoretically a pump should be able to raise water 10.4 m up to the cylinder. However, because seals and valves can never function perfectly, the absolute limit is 6.7 meters. Where pumps are locally made tolerances are usually greater so that the practical limit is 6.5 m or even slightly less.

Elevation above sea level also plays a part in determining the practical limit of pumping height because the higher above sea level the less atmospheric pressure there is to push the water up. (See Chart.)

There is no theoretical limit to how far a cylinder can push water up above itself if the pump parts are strong enough. Practically, however, hand pumping over distances greater than about 30 m becomes difficult because of the pressure exerted by the 30 m column of water. To reduce this pressure, most pump manufacturers use progressively smaller cylinders at increasing depths. This reduces the surface area of the piston and therefore the pressure, but it also reduces the output of the pump. In arid hard rock regions where other water lifting techniques are not feasible, hand pumps have been used at depths greater than 50 m.


MAXIMUM SUCTION HEAD OF RECIPROCATING HAND PUMPS AT DIFFERENT ALTITUDES FOR WATER AT 60°F (15.6°C)

2. Lift pumps/lift and force pumps

If you plan to use the pump to force the water above the level of the pump spout, you will need a "lift and force" pump. The only difference between this and the simple lift pump is that the lift and force pump has a stuffing box around the pump rod at the top of the pump body to prevent water from flowing out that way. (See Figs. VII-3 and VII-4.)

If you are considering ordering a deep well pump, you will also have to decide whether the pump should have an extractable or non-extractable cylinder. (See Figs. VII-5 and VII-6.)

• An open or extractable cylinder is connected to a drop pipe which is slightly larger than the piston assembly in the cylinder. This allows the piston to be removed by simply pulling the pump rod up. The large diameter drop pipe is more expensive, heavier, and more difficult to work with.

• A closed or non-extractable cylinder is connected to a smaller diameter drop pipe which will not permit removing the piston assembly by itself. Instead the whole length of pipe must be removed from the well and the cylinder disconnected to permit access to the piston assembly.


FIG. VII-4. SHALLOW WELL; LIFT AND FORCE PUMP


FIG. VII-5. NON-EXTRACTABLE CYLINDER & FIG. VII-6. EXTRACTABLE CYLINDER

The cup seals in the piston assembly need to be changed every three months to three years, depending on how much use the pump gets, the cylinder material, and the quality of the water. In cast iron cylinders the first cup seals tend to wear faster than later seals, perhaps due to an initial honing action. For a closed cylinder changing cup seals will require some kind of heavy lifting device to be able to remove all the pipe and gain access to the cylinder and the piston assembly with its cup seals. The same operation performed on an open cylinder will simply involve disconnecting the pump from the pipe and pulling up the pump rod with the piston assembly attached to its bottom end.

C. Difficulties with Piston Pumps.

All piston pumps present certain difficulties in practical, everyday use.

• The cylinder will be seriously damaged if sand is pumped with water. Sand scratches the cylinder wall and wears out the cup seals.

• There is the problem of cup seal wear. The smoothness of the cylinder wall largely determines the wear rate of seals. Brass is commonly used because it has a smoother finish than cast iron or steel and will not corrode but cast iron is probably the most commonly used cylinder material. Steel cylinders are rare. Experiments are now underway with plastics and resin cylinders, cylinder liners and cup seals. The initial results are promising.

• The pump rod and handle can present problems. Most handle arrangements do not pull the rod straight up and down but allow some lateral movement. This back and forth movement adds to the wear on both the pump rod and the cup seals. For a regular handle arrangement to come close to straight up and down motion, there must be three pivot points which add to the maintenance. However, a new arrangement developed in India, the Jalna-type pump, has one pivot point and pulls the rod straight up and down. (See Fig. VII-7 and VII-8.) The "Mark II" is the latest Indian development in Jalna-type pumps and is being used in UNICEF assisted projects in India and in some African countries.


FIG. VII-7. JALNA PUMP HEAD


FIG. VII-8. LOCALLY MADE VARIATION OF JALNA PUMP

D. Other Types of Pumps

There are too many other types of water pumps to mention all of them here, but a few should be briefly noted.

1. Diaphragm Pumps

Diaphragm pumps operate similarly to piston pumps with the diaphragm going up and down causing water to move through the pump as two valves alternately open and close. (See Fig. VII9.)

They offer several advantages:

• There is no sliding friction of a seal rubbing against a cylinder wall as in a piston pump.

• Particles as big as the valve openings can be pumped, with little or no damage to the pump.

• A small capacity pump of this type could be easily manufactured by a local machine shop.

There is also one chief disadvantage:

• An uneven stress is exerted on the diaphragm causing it to wear more quickly around the piston.


FIG. VII-9. DIAPHRAGM PUMP

2. Helical Rotor Pumps

This is a modern type of pump with a spiral-shaped interior design which is preferred in several developing countries because of the extremely limited amount of maintenance that is required despite the pump's high cost. It will pump almost anything that is capable of being forced through its pumping unit with little or no damage to it.

Two handles are used to drive the gear which turns the shaft with the rotor, on its bottom end, which turns inside a rubber stator to move water upward. (See Fig. VII-10.) The pump is designed in such a way that the weight of the water is supported on a set of bearings, as opposed to piston pumps which support the weight of the water through the pump rod and pump handle. Unlike standard rotary pumps, the height to which water can be pumped with a helical rotor is not determined by the speed of the pump.


FIG. VII-10. HELICAL ROTOR PUMPING UNIT

3. Bucket pumps

A series of buckets attached to a chain or rope pick up water and dump it into the spout as the handle is turned. This type of pump can be easily made from locally available materials. (See Fig. VII-11.)


FIG. VII-11. BUCKET PUMP


FIG. VII-12. CHAIN PUMP

4. Chain Pumps

Leather or rubber discs usually attached to a chain trap water in the pipe and push it up through the pipe to the spout as the handle is turned to move the chain. This type of pump car. be readily modified to make it suitable for local manufacture. (See Fig. VII12.)

5. Motorized pumps

Motorized pumps are normally not appropriate for rural water supplies where a limited amount of water is needed. The energy required to power these pumps is usually expensive, not readily available or both.

The motorized pumps most commonly used for pumping water are:

• Centrifugal pumps which rely on an outside power source to turn a rotor fast enough to both lift and force water. (See Fig. VII-13.)


FIG. VII-13. CENTRIFUGAL PUMP


FIG. VII-14. TURBINE PUMP

• Turbine pumps which also rely on an outside power source to turn a rotor fast enough to move the water. The turbine rotors must be submerged. (See Fig. VII-14.)

6. Hydraulic Rams

Hydraulic rams cannot be used to lift water from a well, but in the proper situation can be very useful in pumping water from one location to another. Rams are most often utilized to move water from an open body of water above the ram to a storage tank or cistern which is higher than the level of the open body of water.

E. Manufacturing a Pump

Another approach to the installation of pumps which has been successful in some areas is to purchase only that part of the complete pumping unit which needs to be carefully machined. The rest of the pump can be assembled from locally available materials, with the obvious advantages of familiarity and availability.

The most widely used pump of this type is composed of a cylinder assembly,purchased from a manufacturer, attached to locally available galvanized drop pipe. The pump stand, handle and spout can be assembled from wood and pipe. (See Fig. VII-15.)


FIG. VII-15. LOCALLY MADE PUMP HEAD

 

Appendix VIII: Water treatment in wells

A. Well Disinfection

After a well is built, the whole structure should be carefully disinfected. Disinfection is needed to kill any possibly harmful bacteria that could be transferred from the pipe or concrete lining to the water and then on to the people who consume the water.

The well can be disinfected by adding enough chlorine to the well water to produce a strong chlorine solution. This solution can then be used to rinse off the rest of the well and so disinfect it.

1. First, the volume of the water in the well will have to be determined.

NOTE: The volume of water in a circular well can be easily computed by measuring the depth of the water and the diameter of the well. Multiply (water depth) x (1/2 diameter) x (1/2 diameter) x (3.1416). Expressed another way this becomes: Volume = (depth)(radius)² (3.1416).

2. From Table VIII-1 find the amount of chlorine that will have to be added to the computed volume of water to produce a strong chlorine solution.

3. Dissolve the required amount of the chemical in a bucket of water before adding it to the well. Add no more than 100 g of bleaching powder or calcium hypochlorite to each bucket of water.

4. Pour the solution into the well. It is best to agitate the water to insure that the chlorine is evenly mixed.

5. The strong chlorine solution should be left in the well for at least 12 hours and preferably for 24. It must be stressed that this strong chlorine solution is not suitable for humans or animals.

6. After the 12 to 24 hour contact time, the strongly chlorinated water should be pumped from the well until the residual chlorine level is below 0.7 mg per liter of water. (See below.) The pumping equipment to be installed on the well can be disinfected by using it to remove the excess chlorine. Choose a disposal place for the chlorine solution where it will have as little contact with plant and animal life as possible.

B. Water Disinfection

Water can be easily disinfected by adding to it one of several commonly available chemicals which contain chlorine. The most common type of household bleach is a mild chlorine solution which can be used to disinfect water.

The amount of chemical or solution needed to disinfect water will depend on the degree of contamination of the water and the amount of chlorine present in the chemical. However, in most cases where the water is clear with no suspended solid particles, the following disinfection procedure can be used.

1. Determine the volume of water to be disinfected.

2. Find the amount of chlorine compound that will be needed to disinfect that volume of water. (See Table VIII-2.)

3. Dissolve the required amount of chemical in a bucket of water before adding it to the water to be disinfected. Add no more than 100 g of bleaching powder or calcium hypochlorite to each bucket of water.

4. Pour the bucket of chlorine solution into the water to be disinfected. Agitate the water to ensure good mixing.

5. When the chlorine residual (See below.) in the water drops below 0.2 mg per liter, this disinfection procedure should be repeated.

C. Chlorine Residual

The chlorine residual is the amount of chlorine that is left in treated water. Chlorine is used up as it disinfects. Add enough chlorine to the water so that there is a little left over (the residual) after the chlorine has had at least 30 minutes to react with and kill all the living organisms in the water. This assures that all the disease causing bacteria have been destroyed and that there is still some chlorine available to kill other contaminants which might enter the water at a later time.

The recommended chlorine residual is 0.5 mg per liter. A higher residual will cause an obvious chlorine taste in the water. Above 3.0 mg per liter chlorine concentration can cause diarrhea.

Chlorine residual is easily checked with any of the commercially available color comparators. Most of these use an "orthotolidine solution", which turns progressively more yellow at higher chlorine residuals.


TABLE VIII-1 - AMOUNTS OF CHEMICALS REQUIRED FOR A STRONG CHLORINE SOLUTION CAPABLE OF DISINFECTING WELLS AFTER THEIR CONSTRUCTION*


TABLE VIII-2 - AMOUNTS OF CHEMICALS NEEDED TO DISINFECT A KNOWN QUANTITY OF WATER FOR DRINKING*

 

Appendix IX: Rope strength


Rope strength

This chart is based on a similar chart found in Engineer Field Data (1969) FM5-34, Headquarters Department of the Army, 554 pp. The original chart was given in English units which have here been converted to metric units.

The safe loads listed are for new rope used under favorable conditions. These have been calculated by dividing the breaking strength of the rope by 4. As rope ages or deteriorates, progressively reduce safe loads to one-half of the values given.

Here is an example of how the chart can be used.

A 1 meter high lining ring 10 cm thick with a 1.2 m interior diameter contains 0.41 m³ of concrete. Since concrete normally weighs about 2300 kg. per m³ the lining ring weighs about 943 kg. or 0.943 tons. A new manila rope with a diameter of at least 2.54 cm and a circumference of 7.98 cm will be needed to safely handle the lining ring.