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close this book A training manual in conducting a workshop in the design, construction, operation, maintenance and repair of hydrams
close this folder Session 2: Introduction to hydrams (3½ hours)
View the document Handout 2A: Potential energy
View the document Handout 2B: Hydram installation
View the document Handout 2C: Typical hydram
View the document Handout 2D: Glossary of terms for session 2
View the document Handout 2E: Hydram training workshop participant site information

Session 2: Introduction to hydrams (3½ hours)

Time: 3½ hours


By the end of this session trainees will be able to:


articulate basic issues of water supply in their communities and the implications for hydram projects;


approximate amount of water a system must deliver;


accurately describe how hydrams work;


articulate principles underlying how a hydram works;


determine amount of water that can be pumped from a hydram given the flow rate and the height of the source, and the height of the delivery point; and


use standardized notation/terms.


Part I of this session is a technical introduction to the device, providing a basic understanding of how and why it works. It presents the relationship between potential energy and the amount of flow that a hydram can deliver. Given that as a basis, trainees will follow the water flow from a source, through the ram (actual or demonstration) to a delivery point, develop an equation that describes the relationship, and solve problems. Part II examines critical issues involved in the installation of a hydram system, including access to water, present systems, needs, use and demands for water, and establishes a context for the technical training.


Handouts 2A, 2B, 2C, 2D, 2E (2A and 2B reproduced on flipchart)


A working hydram or hydram model


A physical demonstration of potential energy e.g., a pegboard with movable pegs, colored string and weights.


Problems and examples should be written in appropriate units of measurement.




1. Introduce session with a brief statement about the general application and history of hydrams, including use and revival in the U.S.

See Foreword for historical background

2. State the objectives of this session and rationale for two parts.


1. Ask for definition of potential

Use notation consistent with

energy. Write it on the board.

handout, i.e.,

Ep= m x h or Ep = w x h.

Using attachment 2A, or a peg board,

If group seems unfamiliar

demonstrate how a falling mass can

with concept, the peg board

be used to lift a mass to a higher

will probably be better, and


it should be passed around, so they can try it.

2. Refer to attachment 2B on the flip chart, and demonstrate situation in which a hydram can be used. Show how potential energy relates to the amount of water that can theoretically be pumped to a given height.


3. Point out on the diagram, the following: drive pipe, delivery head, quantity of water entering the ram, and quantity of water delivered

The vocabulary and terms are important at this point; the notation is of less importance but should be introduced

Explain that to standardize notation all terms on drive side are capitalized, and delivery terms are in lower case, i.e.:


drive head = H delivery head = h





entering = Q

delivered = q


drive pipe

delivery pipe


diameter = D

diameter = d


length of

length of


drive pipe = L

delivery pipe = 1


Refer trainees to 2B for complete list, and state that for purposes at this point, it's not necessary to know all of those terms.


4. Now that the general parameters of a hydram installation are known, it is a good time to look at how a hydram works.


5. Using attachment 2C describe the water flow through various parts of the ram. Point out that the impulse valve is open when it starts. Ask questions and bring out the following:

It might be useful to underline each part's name in a contrasting color, as you go through the description.

sufficient water coming into the impulse valve to close it


effect of water's movement being suddenly stopped ("water hammer")


moving through the check valve, into the accumulator


check valve closing, with sufficient water weight and air pressure to force water through the delivery pipe


vacuum being created under the check valve, air suction, snifter


6. Go to the actual installation. Have trainees play with the impulse valve, listen to the rhythm, describe water path again, based on what's heard. Take the valve apart, ask trainees to identify key parts (impulse valve, check valve, snifter, ram body, drive pipe, delivery pipe). If possible take the ram apart, to demonstrate.

This is easily done with a clear PVC pipe demonstration ram; which could be hooked up to an experimental stand.

7. Return to classroom. Ask 1-2 trainees to describe the movement of water and the principles. Clarify any misunderstanding, check use of terms.

The PVC hydram could be helpful here also.

8. Return to the potential energy definition, and make the analogy to amount of water pumped, using QH = qh, as a starting point. State that, because of friction and a number of other factors involved in the construction of the hydram, it's unlikely that all of the water theoretically available will or can be pumped, but that some percentage of it will be pumped. The percentage of water pumped is called the efficiency of the hydram, and is designated by 'n'. There fore, nQH = qtr. Ask the trainees to solve the equation for 'q', since the interest is in knowing how much water can be pumped.

Or refer to efficiency as percentage of energy out; use the description that best suits the technical level of the group.


amount of water delivered = (drive head) x (water entering) x (efficiency) / (delivery head)

If the algebraic manipulation confuses the group, go through this derivation process:

nQH = qh

nQH/h = qh/h

nQH/h = q

9. Review standard units of water flow; i.e., in water flow measurement sessions, measurements are in gallons per minute(gpm)

10. Trainees now should be able to tell the amount of water that can be delivered in hypothetical situations given an assumed efficiency. Ask them to solve the following problem:


A spring is flowing at the rate of 20 gpm. The hydram is located 20 ft. (measured vertically) below the spring. The storage tank is 100 ft above the spring (measured vertically) and the assumed efficiency of the hydram is 50%. How much water can be delivered?

Answer: 2400 gallons per day (gpd)

Ask one trainee to present the process and solution on the board. Check the group to see if everything is clear. Ask trainees to develop other hypothetical situations for the group to solve. Check to see that the process and units are correct. If the arithmetic is wrong continue practicing or a calculator may be used

If the diagram from attachment 2B is on the flip chart or chalk board, these figures can inserted in the appropriate places.

If participants are having problems with the arithmetic, suggest that they form study groups

11. Wrap up by reviewing the sessions objectives, and checking with the group to determine that everyone is comfortable with the concepts, vocabulary and the problem solving.


Distribute the glossary and review key words and concepts.




1. Ask participants to form groups of 5-7, and assign one trainer to facilitate each group. Group Task: Distribute participant site information worksheet and have the trainees fill it out. Then as a group have them:



Discuss responses to questions 1-5.

30 min.


List problems with present water system the hydram would solve; problems/issues that would remain the same and new problems/issues that would be created.

15 min.


Each group is to select 2 major problem areas/issues in the development of the hydram system that will be critical to its success over time

10 min.

2. Share (c) in large group. Ask for implications for their work in communities in introducing this technology.

15 min.

3. Summarize as critical issues to keep in mind as they move through the workshop.