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close this book Water purification, distribution and sewage disposal for Peace Corps volunteers
close this folder Section 5: Construction techniques
View the document Overview:
View the document Scheme
View the document Concrete
View the document Construction at the source
View the document Construction at the pumping station
View the document Construction at storage facility
View the document Construction on supply line
View the document Lesson plans

Section 5: Construction techniques

 

Overview:

The preceding sections have covered the background knowledge that a trainee must have to recognize and evaluate sources of water and to plan the development of a distribution and treatment system. Regardless of the planning, a system is only as good as its construction &flows. This section covers the techniques needed by the volunteer to adequately construct the system he has designed.

The emphasis of this instructional material is on doing. The trainee should learn by doing, for no amount of lecture can impart "how", it is only through doing that the trainee will be able to understand when, for example, concrete is wet enough,

This section covers construction with concrete, and specific projects for building and installing the mayor components of a treatment and distribution system.

SECTION 5: CONSTRUCTION TECHNIQUES

OBJECTIVE: Develop, purify and distribute water in a given community.

TASKS:

1. Develop the selected source to meet the requirements specified in the design.

2. Build an intake site and install intake pumping facilities.

3. Test the water so obtained for sanitary standards.

4. Build a treatment plant appropriate for treating water from the above developed source.

5. Construct a storage tank with a predetermined capacity; apply protective coatings on tank and pipes against heat, chemical corrosion and Insect pests.

6. Lay and connect pipes for the conveyance of water from the distribution reservoirs (storage tank) to the various service connections.

FUNCTIONAL SKILLS:

1. Recall characteristics of various types of sources.

2. Dig, drill, and bore a well in such a way as to obtain maximum yield from it.*

3. Mix concrete of a desired strength.

4. Build protective casing for a well, spring, or pump base.*

(*This skill is optional, depending on the scope of the particular training program.)

5. Build a small pumphouse to specification.

6. Determine conditions which would require low or high lift-pumps for intake of water.

7. Build a screen of wire or other materials of desired mesh around an intake terminal in a pond, lake, stream, river or any other reservoir to keep out silt, water life and vegetation, and the stress from water flow.

8. Recognize relevant treatment processes for water from a given source.

9. Construct or assemble the various treatment processes such as, filters, sedimentation tanks, etc.

10. Connect various treatment stages in their proper order.

11. Read and follow an instruction manual.

12. Put together a prefabricated structure, using reinforced concrete, painting or spraying the needed parts, and welding, soldering or riveting pipes together.

TERMINAL PERFORMANCE TESTS:

1. At a given location develop a water source from underground water which will meet the water demand of the community.*

(*This skill is optional, depending on the scope of the particular training program.)

2. Given raw materials required to produce concrete, mix concrete of a specified strength and show it meets the specification.

3. For a given source, install an intake pump.

4. Given the plan and all materials, build a house over a well (or pump).

5. In a given distribution system. state where you would use: a. Low lift pump b. High lift pump

6. Design and build a model of an intake terminal of a system if the source is: a. Lake or pond b. River or stream c. Well or cistern

7. For a given source of water, carry out purity tests and state what kind of treatment the water requires.

8. Construct separately the various component parts of a treatment system and test the efficiency at the various treatment stages.

9. Given a model treatment plant in the laboratory, assemble the various treatment units in order of performance (e.g., sedimentation-filtering).

10. Given a package of all parts of a tank or pump (or the respective models) with an accompanying instruction manual, assemble the parts and test for proper fittings.

11. Given a storage tank and its gross weight, design a foundation for its elevation to a given height above the ground.

12. Construct a tank of specific volume with reinforced concrete.

13. Given a storage tank and distribution pipes, coat to protect them from: a. Corrosion from ground and atmospheric chemicals b. Excessive heat c. Insect and other pests.

14. In a workshop, join several pipe lengths using different methods at each joint, e.g. welding, riveting, etc.

 

Scheme

HATER DISTRIBUTION SYSTEMS

CONSTRUCTION TECHNIQUES

The following sketch shows the major components of a distribution system that must be planned and constructed. In total, this represents a complete water distribution system, indicating the location of each component relative to the others.


Fig. 38 Distribution System Layout

1) Development

1) Building house

1) Constructing tank

2) Intake

2) Installing pump

2) Installing purification systems

 

Concrete

The material which is used at almost all stages is concrete For this matter, an extensive description of concrete in construction work will be included for convenience.

Concrete is a strong, durable and inexpensive construction material when properly prepared. After concrete has set, there is no simple non-destructive test to evaluate how strong it is. Therefore, the entire responsibility for making concrete a strong material in accordance with specifications rests with the supervisor on the fob and the people who prepare, measure and mix the ingredients, place them in the forms, and watch over the concrete while it hardens.

The most important factor in making strong concrete is the amount of water. Beginners are likely to have too much. See the entry on a slump cone for further details.

The proper proportion of all the materials, designed for the application, is essential. The concrete calculator will help give the proper proportions and amounts, for your job.

Properly graded, clean, sharp aggregate and sand is required to make good concrete. When we glue two pieces of paper together, we spread the glue evenly and in a thin layer, and press firmly to eleminate air holes. In concrete, the cement is the glue, and the sand and aggregate the material being joined.

By properly graded we mean that there are not too many of any one size grains or pebbles. Visualize this by thinking of a large pile of stone all 1 1/2" in diameter. There would be spaces between these stones where smaller pebbles would fit. We could add to the pile just enough smaller stones to fill the largest voids. Now the voids would be smaller yet, and even smaller pebbles could fill these holes; and so forth. Carried to an extreme, the pile would become nearly solid rock, and only a very small amount of cement would be needed to stick it together. The resulting concrete would be very dense and strong.

Sharp aggregate and sand is desirable. Smooth, rounded stones and sand can make fairly good concrete, but sharp, fragmented particles work better because the cement as a glue can get a better grip on a rough stone with sharp edges.

It is extremely important to have the aggregate and sand clean. Silt, clay, bits of organic matter will ruin concrete if there is very much present. A very simple test for cleanliness makes use of a clear wide-mouth jar. Fill the jar about half full of the finer material available, the sand and small aggregate, 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 what 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 cone by putting the sand (and fine aggregate 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 aggregate 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, stirred in two buckets of water you could carry away about 27 buckets of damp sand. The chart does not take this extremely dry sand into account. If your sand is completely dry, add some water to it or else do your measurements 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 a proper cure. 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 so necessary to keep the surface damp continuously.

Mixing the materials and getting them in place quickly, tamping and spading to a dense mixture is important. This is covered on the entry on mixing.

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

CONCRETE CALCULATOR

Use the alignment chart as follows. Make a light pencil mark on the left-most scale representing the area of concrete needed. Make a similar mark on the slanted thickness scale. Draw a straight line through these marks intersecting the third scale. This is the volume of your concrete. If your project has a complex shape, add up the volumes of all the parts before proceeding.

Now mark the total volume of concrete on the third (volume) scale, and the kind of work on the fourth. (See definitions.) A line through these two points will give the amount of fine aggregate needed. Continue on a zig-zag course as shown in the KEY to calculate the coarse aggregate, sacks of cement, and water.

It may be necessary to make slight adjustments to the mix, depending upon the type of aggregate used. The final mixture should be wet enough and workable enough to go into the forms fairly easily, requiring light spading or tamping to produce a dense mixture. Too much moisture produces a weak cement. The figures in the alignment chart do not allow for waste which may run as high as 10%.

All materials can be measured in "buckets" instead of cubic feet. The nomograph will still give the correct proportions. The total amount of concrete produced, however, will depend upon the size of the bucket used as the measure. Most buckets are rated by the number of gallons they can hold. To convert to cubic feet, then, you must know that one cubic foot equals 7.5 gallons. A four gallon bucket would hold 0.533 cubic feet. Incidentally, one cement sack holds exactly one cubic foot, so "buckets" can also be substituted for "sacks" on the chart.

Similarly, if your volume of concrete needed is less than 15 cubic feet, you can multiply this by some convenient factor (say 10) and then divide the amounts of materials the chart says to use by the same factor to get the actual amounts needed.

Definitions used in the chart are given on the fold-out page.

HAND MIXING CONCRETE:

Proper mixing of ingredients is necessary to get the highest strength concrete. Hand mixed concrete made with these tools and directions can be as strong as machine mixed concrete.

TOOLS AND MATERIALS

Lumber - 2 pieces 6' x 3' x 2"

Galvanized sheet metal - 6' x 3'

Nails

Saw, Hammer-

Or concrete for making a mixing floor. (About 10 cubic feet of concrete are needed for an 8' diameter mixing floor made 2" thick with 4" high rim.)


Concrete calculator

Kind of work

- "5" means "5 gallon paste" which is concrete subjected to severe wear, weather, or weak acid and alkali solutions Examples would he the floor of a commercial dairy

- "6" means "6 gallon paste" for concrete to he watertight or subjected to moderate wear and weather Examples: watertight basements, driveways, septic tanks, storage tanks, structural beams and columns

- ''7" means ''7 gallon paste's for concrete not subjected to wear, weather, or water

Examples Foundation walls, footings, mass concrete, etc. where water tightness and abrasion resistance are not important

Fine Aggregate

- Sand or rack screenings up to one quarter inch in diameter Should he free from fine dust, loam, clay and vegetable matter or the concrete will have low strength Particles should vary in size, not all fin. or coarse.

Coarse Aggregate

- Pebbles or broken rock from 1/4" up to 1-1/2". Nothing coarser than 3/4" should he used for a 5 gallon paste

Condition of Sand

- Dry-feels slightly damp hut leaves very little water an the hands

Average-feels wet; leaves a little water on the hands

Wet-dripping wet, leaves quit. a bit of water on the hands

Gallons

- The chart is hosed on the U S. Gallon (This is 0. 835 of on- Imperial Gallon )

Material From

-Designed by John Bickford from data furnished by the Portland Cement Association of Chicago, Illinois, U. S. A

DESIGNER BY JOHN BICKFORD FOR VOLUNTEERS FOR INTERNATIONAL TECHNICAL ASSISTANCE INC. 9\28\62


Fig. 40 CONCRETE MIXING

On many self-help projects the amount of concrete needed may be small or it may be difficult to obtain a mechanical mixer. Under these circumstances hand mixing of the concrete will be necessary and, if a few precautions are taken, the quality of concrete can be made equivalent to that from a mechanical mixer.

The first requirement is a watertight and clean base upon which the mixing can be done. This can be a wood and metal mixing boat (Fig. 40A) or a simple round floor made of concrete (Fig. 40B).

The ends of the wood and metal mixing boat are curved to make emptying easier. The raised edge of the concrete mixing floor serves to prevent loss of water form the concrete.

The procedure for mixing is similar to that for mechanical mixers in that the dry materials should be mixed first. As a minimum it is recommended that the pile of stone, sand, and cement be turned completely once. It should be completely turned a second time while the water is being added. Then it should be turned a third time, Anything less than this will not adequately mix all materials. When this last step is completed the mix can be placed as usual.

Correctly placing the fresh concrete in the forms or shuttering is important in making strong structures. The wet concrete mix should not be handled roughly either in carrying to the shuttering or putting into the shuttering. In either case it is very easy, through joggling or throwing, to separate the fine from the coarse material. We have said before that the strongest concrete comes when the various sizes of aggregate and cement are well mixed together. The concrete mix should be firmly tamped into place with a thin (3/4") iron rod.

Be sure to rinse concrete from the mixing boat and tools when finished each day with the work. This will prevent rusting and caking of cement on them for smooth shinny tool and boat surfaces make mixing surprisingly easier, and the tools will last much longer. Also try to keep wet concrete off your skin, for the material is somewhat caustic.

When the shuttering is full the hard work is done, but the process is not finished. The shuttering must be removed and the concrete protected until adequate strength is attained. The hardening action of cement begins almost immediately after the water is added, but the action may not be fully completed for several years.

Concrete reaches the strength used in the designing after 28 days and is strong enough for light loading after 7 days. In most cases the shuttering can be removed from standing structures such as bridges or walls after 4 to 5 days. In small ground supported structures such as street drains it is possible to remove the shuttering within 6 hours of completion provided this is done carefully. Special conditions, usually specified on the plans, may require leaving the shuttering in place for a much longer time.

During the early stages of hardening or curing the cement in the concrete continues to need moisture. If there is insufficient water available the cement is unable to complete its job of gluing the aggregate together. Because of this, it is recommended that new concrete be protected from drying winds and the sun, and that the surface of the new concrete be kept damp. For cement floors or open construction a covering of banana or palm leaves will be adequate, but these should be given a sprinkling of water at least once and perhaps twice each day for a period of not less than one week.

TESTING THE STRENGTH OF CONCRETE

The Slump Cone

The following tools and materials are needed:

Heavy galvanized iron

Strap iron - 4 pieces 1/8" x 3" x 1"

16 iron rivets 1/8" diameter x 1/4" long

Wooden Dowel 24" long, 5/8" diameter


Fig. 41 The Slump Cone

In making reinforced concrete, it is important to have just enough water to make the concrete settle finely into the shuttering (forms) and around the reinforcing when it is thoroughly tamped.

The easiest way is to look at the mix and at the way the workmen place the wet concrete. If the mix appears soupy and the aggregate shows up clearly in the mix, then it is too wet. At the same time it will be noticed that the workmen dump the mix into the shuttering and do very little tamping because. if they do any amount of tamping, large amount of water will immediately appear on the surface. The workmen will soon complain if the mix is too dry.

A more accurate method of making a decision on the proper amount of water is to use the slump test. This test requires a small cone made of fairly strong metal and open at both ends. Dimensions of the cone and tamping rod are shown in the sketch. Once this simple equipment is available the slump test becomes very easy. The steps to follow are listed below.

1. Set the slump cone on a smooth clean surface and stand on the hold-down clips at the bottom of the cone.

2. Have someone fill the cone to 1/4 of its height and tamp this layer 25 times.

3. Fill the cone to 1/2 its height and tamp this layer 25 times.

Avoid tamping the first layer again.

4. Fill the cone to 3/4 its height and tamp 25 times. Avoid tamping the previous layers.

5. Complete filling of the cone and tamp this layer 25 times.

6. Step off the hold-down clips and lift the cone vertically and very carefully off the concrete.


Fig. 42 Slump cone plans

Since this process will have taken only a few minutes the concrete will still be very soft when the cone is removed and the top will fall to some extent while the sides bulge out. This is called the slump. Obviously, if the mix is too wet the concrete will lose its shape completely and become just a soft pile. A good mix, as far as the water-cement ratio is concerned will slump about 3" to 4" when the cone form is removed. It is well to keep in mind that dirty or muddy water can cause as much trouble as aggregate with excessive fine materials. Use clean or settled water.

 

Construction at the source

DEVELOPING THE SOURCE:

Sources which require much development are ground water sources. The development of wells, is covered extensively in the "well construction manual". Constructions in spring development are similar to those for wells.

The quantity of water from a spring can very often be substantially increased by digging out the area around the spring down to an impervious layer to remove silt, decomposed rock, and other rock fragments and mineral matter (usually calcium carbonate) sometimes deposited by the emerging ground water. In doing this, particular care should be taken, especially in fissured limestone areas, to avoid disturbing underground formations to the extent that the spring is deflected in another direction or into other fissures.

Springs in general, and gravity springs in particular, are subject to contamination in the area close to the point of emergence. A thorough sanitary survey should be conducted before development work is initiated. Such a survey should yield information on the origin of the ground water, the nature of the water-bearing strata, the quality of the water, its yield in various seasons of rainfall, the topography and vegetation of the surrounding area, and the presence of possible sources of contamination. To protect the spring, the collection structures should be so located and built as to force surface water to pass through at least 10 ft of soil before reaching the ground water. It is also customary to exclude all animals and habitations from a substantial area (perhaps 100-300 ft), around the collection chamber, and to dig a diversion ditch above and around this to interrupt surface run-off and divert it away from the groundwater collection zone. Springs emerging from solution channels in limestone formations should be carefully investigated and observed, since under such conditions very little, if any, natural filtration takes place in the ground.

Such springs are likely to yield grossly polluted and turbid water soon after heavy rains, and should not be used as a source of domestic supply without a thorough study, including frequent bacteriological examination, and without the provision of corrective measures, such as filtration and/or disinfection. Other protective measures are discussed below.

Springs, especially those which can be piped to the user by gravity, often provide an economical and safe solution to the water-supply problems of rural communities. Fig. 43 show typical methods of collecting water from springs.

INTAKE STRUCTURE

The intake may consist of a submerged pipeline used with a submerged crib or a screened bellmouth at the open end. It should be placed well below the water surface since the water is cooler at a greater depth and, also. because of ice formation In cold climates; but it should not be close to the river bottom, in order to avoid sediment and suspended matter moving along there. The intake should also be located some distance from the shore and should be large enough for entrance velocities to be kept to a minimum, preferably less than 6 in. per second. Fig. 43 shows a simple intake structure for small water-supply systems from rivers or lakes.


Fig. 43 Small Intake Structure

Reproduced from Hardenbergh W. A. (1952) Water supply and purification, p. 52, by kind permission of international Textbook Co., Seranton, Pa., USA

Intakes from small streams frequently require the construction of small diversion dams. In this manner provision can be made for a sufficient depth of water at all times above the intake pipe; for the settling of suspended matter, thereby reducing the turbidity of the water; and for keeping floating leaves and other debris from obstructing the intake structures. Depending upon circumstances such as the depth of water in the river, location, and degree of permanency of the structure, a floating intake made of empty oil drums held in place by a suitable frame and supporting a flexible inlet hose may be used. Intakes should always be designed to function with a minimum of attendance. More elaborate 'designs are shown in Section 2.

 

Construction at the pumping station

The pump-house will vary, depending on the type of pump used, the materials available and the capacity of the system. In general, the pump base should be built of concrete.

Precuts concrete slabs are suitable for floors and walls of a cheap but efficient pump-house.

Corrugated iron (or asbestos) sheets should be used for roofs for larger houses. For small houses, precuts concrete slabs can also be used.

The roof (at least part of it) should be removable so that a crane can be used to haul out the pump in case of repairs.

The manufacturers usually supply a manual for installing their pumps. Such directions must be followed closely. If necessary; an expert should be called to install the pumps, especially where electric power is used to run the pump.

 

Construction at storage facility

STORAGE TANKS

Storage tanks can be built on high grounds in which case they are termed ground-level reservoirs, or they are elevated reservoirs.

Ground-level reservoirs are usually built of masonry, mass concrete, or reinforced concrete, according to the materials and local skill available (see below)


Fig. 44 Ground-Level Reservoirs

A = Cross-sections of reservoir

B = Types of walls for reservoirs

C = Sketch detail of manhole opening in reservoir cover

D = Typical valve arrangement for ground-level reservoir with two compartments

Aa = Effluent

Bb = Supply

Cc =Overflow

Dd = Drain


Typical Spring Collection-Chamber For Towns

A = Ground level

B = Water-bearing formation

C = Impervious stratum

D = Collection chamber

E = Opening protected by a stone-and-gravel pack in order to exclude sand and debris

F = Collecting room

G = Measuring weir

H = Measuring rod, bottom of which is level with lower edge of weir

I = Outlet pipe to reservoir or town

J = Floor drainage

K = Locked entrance door

L = Screened opening through door for ventilation purpose

M = Diversion ditch for surface run-off. Should be at least 15 m (49 ft) away from the collection structure


Property Protected Spring (I)

A = Protective drainage ditch to keep drainage water a safe distance from spring

B = Original slope and ground line

C = Screened outlet pipe: can discharge freely or be piped to village or residence

Springs can offer an economical and safe source of water. A thorough search should be made for signs of ground-water outcropping. Springs that can be piped to the user by gravity flow should be checked.


Property Protected Spring (II)

A = Protective drainage ditch to keep drainage water a safe from spring

B = Screened outlet pipe: to discharge freely or be piped to village or residence

In order to prevent leakage in the reservoirs, the following should be done:

1. Build concrete walls with as few joints as possible

2. Copper or polyethylene strips should be built in vertical joints if possible.

3. Paint the whole inside surface with a bitumen compound or with a solution of sodium silicate (water glass).

4. Render interior surface with about 3/4 inch thickness of mortar composed of water-proof cement and sand, after thoroughly rough ending the surface to be rendered to ensure a good key.

Elevated reservoirs may be of reinforced concrete or-of steel. Reinforced concrete is suitable when many tanks of similar size are to be built in a series of villages, so that the system is used over and over again. The construction techniques involved are the same as for ground-level storage, except that the elevating walls should be built first.

Steel reservoirs are suitable for single reservoir plans. The tank can be ordered from the manufacturers and comes complete with the accompanying assembly manual which is easy to follow. The tower foundations are to be locally built of concrete.

Steel reservoirs can also be used for ground-level tanks on rocky sites or in areas where masonry rocks are scarce. In such cases, the tank must be slightly elevated to allow painting of lower parts. Elevated storage tanks have valves to stop overflowing. When a float valve is used to control the level in the tank, the overflow should never come into action if the valve is working properly. In the case of a "floating" tank it is usual to control the inflow through a float valve and the outlet joins the delivery pipe through a non-return (see Fig. 48 ). A depth gauge operated by a float and wire shows the amount of water within the tank, and is visible from the outside.


Fig. 48 Elevated Storage Tank

Outlet always taken from 6 in above tank floor; wash-out at extreme bottom of tank

A = Diagrammatic arrangement of pipes when overhead tank acts as balancer ( floating tank ). Not suitable for use with reciprocating pumps.

B = Diagrammatic arrangement of pipes when pumping direct to storage tank

When a float valve is not used, there is no control on the depth of water except the intelligence of the operator of the supply pump and the overflow, and carelessness in adjusting the hours of pumping to the draw-off can result in considerable waste, while the farther the tank is from the pump-house the easier it is to overlook such waste. The simple indicator shown below is one way of reducing this to the minimum as, properly sited, it can be seen for a considerable distance. However, the nearer the tank is to the pump-house the easier this control becomes.


Fig. 49 Water-Level Indicator For Elevated Storage Tanks

A = Suitable indicator for top two three feet of water in tank

B = Appearance of indicator from a distance; it should be orientated so that it appears against the skyline from observation point; it can be seen clearly a mile away.

C = Section at a, showing construction and operation of lower indicator

In the construction of storage facilities, the following provisions should be made:

1. Manhole covers must be tightly fitting to prevent surface water from entering the reservoir . They should be locable.

2. Surface covers must be water-tight and light-proof to prevent algae growth.

3. Ventilation must be included to let out air as water fills the tank. These must be covered with fine-mesh wires (not less than 18-mesh).

4. Inlet and outlet pipes, overflow and wash-out pipes should have mesh at their open ends. The outlet pipe should be 6 in. above the bottom of the tank. If the tank has concrete floors, the floor should slope towards the wash-out pipes to enhance cleaning. The diagrams below illustrate the proper design for a concrete storage tank.


Fig. 50 Storage Tank


Fig. 51 Manhole covers


Fig. 52 Typical valve and toy


Fig. 53 Piping Installation

WATER PURIFICATION SYSTEM

Water purification systems are usually incorporated in the storage tanks. Where only disinfection (chlorination) is required, the treatment tank can act as distributing reservoir. The cistern is a typical storage-purifier combination.

The cistern filter is a sand filter which keeps organic matter from entering the cistern. The water may then be disinfected and stored in the cistern. The diagrams below show the construction design for such a filter.


Fig. 54 Cistern Filters

A catchment area always collects leaves, bird droppings, road dust, insects, etc. A cistern filter removes as much of these as possible before the water enters the cistern.

The sand filter is usually built at ground level and the filtered water runs into the cistern, which is mostly underground. The largest pieces, such as leaves, are caught in the splash plate. The splash plate also serves to distribute the water over the surface of the filter, so that the water does not make holes in the sand. A piece of window screen forms the splash plate.

Most filters are made too small to handle the normal rush of water from rainstorms. This results in the filter always overflowing or a channel being dug in the sand, which will ruin the filter. The filter area should be not less than one-tenth of the catchment area. A typical filter area would be 4 feet by 4 feet for a family-sized unit with average rainfall intensity.

About every 6 months, the manhole cover to the filter must be removed and the filter cleaned. Remove all matter from the splash plate and scrape off and remove the top half-inch of sand. When the depth of sand becomes only 12 inches, rebuild it with clean sand to the original depth of 18 inches.

A simple way to discard the first runoff from the roof, which is usually mostly leaves and dirt, should be provided. This will make your filter last longer between cleanings. The easiest way is to have a butterfly valve (like a damper in a stovepipe) in the downspout. After the rain has washed the roof, the valve is turned to allow the runoff water to enter the filter. A semiautomatic system is shown in Fig.

When building the filter, it is important to insure easy cleaning and to use properly-sized sand and gravel. The filter is usually mounted right on the cistern but can also be close to it. It rust have a screened overflow.

Water Purification Plant

Tools and Materials

3 barrels, concrete tanks or 55-gallon drums

1 eight inch funnel or sheet metal to make a funnel

2 smaller tanks, about 5 gallon or 20 liters in size, equipped with float valves

4 shut-off valves

1 throttle or needle valve (clamps may be used instead of the valves, if hose is used) some pipe or hose with fittings hypochlorite of lime or sodium hypochlorite (laundry bleach)

This plant can be used in small systems, using laundry bleach as a source of chlorine.

The water purifier should be made as in the drawing. The two large barrels on top of the structure are for weakening the bleach. The two smaller tanks on the shelf below are for holding equal amounts of weakened bleach solution and of water, at a constant pressure. This makes a constant flow of the solution water, at the same speed, into the hoses leading to the mixing points. The mix is further controlled by the valves and may be seen through the open funnel. If a throttle valve is not available, a shut-off valve may be used and a throttle action obtained by this valve and valve #4 in series.


Fig. 55 Chlorination system

Placing the two barrels at a height of 10 feet causes a pressure of only about five pounds a square inch. Thus the plumbing does not have to be of high quality except for valve #1 and the float valve of the water holdup tank, if the rain water supply is under higher pressure.

Sometimes special chlorinators are required; in which case when hypachlorinators are ordered, the following data should be furnished to the manufacturers:

If water is pumped:

1. Sketch of pumping installation

2. Number and type of pumps

3. Manual or automatic operation

4. Pumping rate (liters/second or gallons/minute) and total water pumped per day (cubic meters or gallons)

5. Electric current available (volts, phase, cycle)

6. Pressure on pump discharge (minimum and maximum)

7. Suction lift

8. Sizes of suction and discharge pipes

9. Other data (space available for installation, sizes of foot valves, check valves, etc.)

For gravity system:

1. Sketch of system, indicating source of water supply and distances

2. Size of main

3. Size of meter, if any, giving make and description

4. Pressure at meter or point of installation (minimum and maximum)

5. Rate of flow (minimum and maximum)

6. Average daily flow (cubic meters or gallons per day)

7. Fire flow, if any (liters/second or gallons/minute)

8. Allowable loss of pressure (m or ft)

9. Other data (space available for installation, etc.)

Boiler for Potable Water

Sometimes it is easier to boil drinking water than to disinfect. The following design can provide enough safe water for a smell community with a distribution system, since it would require a lot of fuel to boil enough water for the system.

Tools and Materials

1 - 55 Gallon drum

1 - 3/4" Pipe Nipple 2" long. Quantity of bricks for two layers of bricks to support drum.

1 - bag of cement plus sand for mortar and base of fireplace.

1 - large funnel and filter medium for filling.

1 - metal plate to control draft in front of firebox.

1 - 3/4" valve, preferably all metal such as a gate valve to withstand heat.


Fig. 56 Boiler for Potable Water

This drum for boiling of drinking water is intended for use in your residence to provide a convenient method for preparation and storage of sterile water. The fireplace is simple, oriented so that the prevailing wind or draft goes from front to back of the drum between the bricks. A chimney can be provided but is not necessary.

The unit has been tested in many Friend's workcamps in Mexico and elsewhere. A 55 gallon drum would normally last a 20 person camp group for an entire week, and certainly would provide adequate safe water supply for two or three individuals for a much longer time. Water must boll at least 15 minutes with steam escaping around the completely loosened filler plug. Be sure that the water in the pipe nipple and valve reach boiling temperatures by purging about two liters of water out through the valve while the drum is at a full boil.

 

Construction on supply line

Pipe trenches must slope uniformly to avoid pressure variations in the pipes. Whenever a pipe has to pass over a gap in the trench, structures should be installed to support the pipes, especially at the joints. Once laid, the pipes should be coated, and accurately recorded in the systems map.

Different joints are used for different connections, The choice of a joint depends on the number of branches desired at a point. Positions of joints with many branches should be marked and protected as it is usually the main source of trouble.

The diagrams attached illustrate the various joints used in distribution systems. The supplier should provide simple guides, for joining pipes. If not available, a plumber's manual should be obtained. This should not prove necessary however, since this often involves only screwing parts together.

VALVES

Valves are used for specific purposes:

a. Gate valves - control the flow of water. Should be placed in junctions so that sectional repairs can be carried out without interruption of service. Should have manholes and be easily accessible. b. Check valves - allows one directional flow only. Used between pumps and pipe lines.

c. Air-Valves - allows air to escape from high points in the pipelines

d. Pressure-reducing valves - to reduce water pressure in pipes of any desired value.

METERS are not essential in rural water supply systems.

HYDRANTS - Where fire protection is provided, these should be designed to provide connections for 2 1/2 inch diameter fire hoses.

SERVICE PIPE -Connects street distribution pipe to the houses plumbing system. Should be rigidly connected to the street pipe.


Fig. 57 American standard cast iron flange fittings

 

Lesson plans

CONSTRUCTION TECHNIQUES

LESSON NO. 1

LESSON OBJECTIVE: To build an intake site and install pumping facilities.

TOPIC

INSTRUCTIONAL PROCEDURE

SUPPLEMENTAL MATERIALS/RELATED READING

Intake Structures

Discuss need for and effectiveness of, various types of intake structures.

WHO Monograph Series #42,

Chapter 5.

 

Take field trip to an open source with a visible intake structure

Intake Structure.

Designing Intake Structures

Divide class in small groups. Let each design (and construct) a simple intake structure.

structure.

 

Draw conclusions indicating when to use an intake structure.

 

Pump Selection

Discuss in class what sort of lift pump is required.

Section 3 on Pump Selection.

Concrete in Construction Work

Introduce concrete in construction work - its structure.

Concrete blocks.

Raw ingredients for making concrete.

 

Demonstrate how to determine the amount of each ingredient.

 
 

Demonstrate how to mix concrete properly.

 
 

Let students determine the required amount of each ingredient using the chart.

 

Testing Concrete

Demonstrate the test for strength.

Slump Tester.

 

Discuss in class the need for reinforcing concrete.

Concrete pipes:

a) reinforced

b) not reinforced.

 

Test reinforced concrete and one not reinforced.

Strain-Stress Testing Machine.

Bu Tuing a Pump House

Discuss when a pump house is necessary.

 
 

In the field demonstrate how to build a pump house. (If not possible, the students should be given chance to work with a building crew).

Building Materials.

 

CONSTRUCTION TECHNIQUES

LESSON NO. 2

LESSON OBJECTIVE: To teat water obtained from a source for drinking water standards.

TOPIC

INSTRUCTIONAL PROCEDURE

SUPPLEMENTAL MATERIALS/RELATED READING

Testing Water

Samples

Ask students to recall the characteristics of water that should be tested.

WHO Monograph #42, pp. 46-54.

 

In the laboratory (or in the field) demonstrate how to use the various kits commonly used in the field.

Portable water laboratory field kit. Microfilte tester.

Exercise on Water Tests

Divide class into convenient groups and let each group test for a different pollutant.

 
 

Verify each result.

 

 

CONSTRUCTION TECHNIQUES

LESSON NO. 3

LESSON OBJECTIVE: To construct a treatment system appropriate for simple water purification.

TOPIC

INSTRUCTIONAL PROCEDURE

SUPPLEMENTAL MATERIALS /RELATED READING

Assembling

Treatment Systems

Ask students to recall the functions of component parts of various treatment processes.

Sand filters, chlorinators, aerators, settlement basins, chemicals, measuring vessels.

 

Divide students in working groups.

Section 4 on the functions of component parts of various

 

Let each assemble a most complete purification system. processes.

 
 

Test the efficiency of the constructed treatment systems

 

 

CONSTRUCTION TECHNIQUES

LESSON NO. 4

LESSON OBJECTIVE: To install a storage tank and distribution pipes properly suited to the local environment.

TOPIC

INSTRUCTIONAL PROCEDURE

SUPPLEMENTAL MATERIALS/RELATED READING

Building a Distribution

Reservoir

Take a field trip to storage sites.

Section 4 on storage tank. Central distribution system.

 

Using model designs, let each student assemble a distribution reservoir.

Plans and model block instruction manuals on assemblage.

 

Stress the importance of outlet, inlet and overflow pipe screens.

Paint and brush (or spray).

 

In a field inspection of local systems, let each student trace a distribution line from reservoir to a house.

 

Pipe Laying

As field exercise, take the whole class to dig a trench and lay 50 ft. of pipe.

Short pipes of different diameters, pipe joints, welding torch

Rivets.