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SWS Rower Pumps - your questions answers

Q1 "I have seen a lot of hand pumps before but the SWS Rower Pump looks most unusual. Please explain how it works and why it is set into the ground at such a strange angle?"

"The Rower Pump looks unusual but it is based on the tried and tested piston pump design. What is unusual is the way the cylinder is half buried and set at an angle of 30" to the horizontal. This lets the operator work the pump by pulling & pushing directly on a T-handle attached to the piston rod itself."

Q2 "Do you mean the valves are just like those of any other piston pump?"

"Yes. The two valves open and close alternately as in other piston pumps but they have been specially designed for both long life and very easy maintenance.

Q3 "Okay, I can see that the pump's mechanism is similar to those of other piston pumps but why is it set into the ground at an angle?"

"The pump is designed to be worked by the body's strongest muscles, including those in the arms, back and legs. When the operator pulls on the piston he uses his whole body and his weight to work the pump. Pulling upwards and backwards is the best way to achieve the maximum force.

Q4 "Most pumps have a pivot and lever. Do you mean to say that the Rower Pump doesn't actually need these features?"

"Yes, that is quite correct. Because the Rower Pump is designed for drawing water from quite shallow depths a direct pull backwards can generate enough force to operate the pump satisfactorily. The handle is wide enough for two children to work together. No pivot means there is less to wear out and go wrong than with other pumps.

diagram

Q5 "Some pumps can be damaged when the handle is banged st the beginning and end of each stroke. Has this problem also been eliminated in Rower Pumps?"

"Yes. There is no tendency for the plunger to be pushed too hard into the pump because it is beyond the operator's comfortable reach, while at the top end of the stroke, if one did pull too hard the whole plunger simply pops out of the pump.

Q6 "If the plunger can be taken out as easily as that isn't theft a problem?"

"Whether this is a problem or not depends on where the pump is being used. If the pump is being used privately for irrigation the owner may very well take the plunger back to his house at night. Similarly, if the pump is out of sight of the village a caretaker can be appointed. This man should live close to the pump so each evening he can take the plunger back to his house having first covered the pump mouth with a tin can or something similar.

Q7 "Can the pump be used by both tall adults and short children?"

"Yes most definitely. As children use the pump they should stand close to it so most of the piston stays in the cylinder. A tall person using the same pump will draw most of the piston out of the pump and stand further back. The angle at which the plunger is worked is the same for both users. It is very important to set the pump at just the right height and angle to achieve the most comfortable operating position. "

Q8 "Is the pump difficult to install and are any special tools needed?"

"No. The pump can be set up using basic hand digging tools such as a hoe and a spade. You also need some wooden stakes and rope so that the pump can be lashed into position before being packed around with earth and clay.

Q9 "What are the main applications for Rower Pumps?"

"Rower Pumps are used for both domestic water supplies and irrigation. Most Rower Pumps used for domestic water supplies are placed beside low level springs or shallow wells. In East Zaire for example, many communities depend on springs for their water supplies but often these springs are at such a low level that the water tends to gather in pools which are easily contaminated when people collect water or animals go to drink. By placing a filter into the water and setting the pump some distance away, one can draw clean spring water before it is polluted and keep people away from the source itself.

Rower Pumps can also used to draw from a variety of shallow wells including open dug wells and tube well screens jetted into sandy river beds. (These are sometimes known as washbores.) In Sudan Rower Pumps draw water from sand filters alongside canals while in Zambia they have been used to de-water hand-dug wells. They can also be used to prime mechanical engine pumps.

Q10 "What fittings are provided at the pump inlet?"

"The pump can be provided with either a l'/2" threaded take-off suitable for a hose connector or, more commonly nowadays, a plain l'/2" pipe onto which a straight socket is glued. The pump is made of the high grade plastic "ABS" but it is possible to glue on either an ABS or a PVC fitting.

Q11 "You say that the Rower Pump requires little maintenance; how much maintenance is actually needed?"

"There are only 2 or 3 components which may need to be changed from time to time; these are all rubber seals. The cup seals receive most wear since they are the only parts of the pump where moving surfaces come into contact. To change the cup seals the piston is withdrawn and the valve removed. The worn cup seals are pulled off and replaced by 2 new ones. This may have to be done every 4 or 6 months but since the piston rod is easily withdrawn these seals can be checked regularly for wear. As the cup seals become worn the pump gradually becomes less efficient so the pump doesn't suddenly stop working. If Vaseline is used to lubricate the seals they last much longer.

The footvalve is also easy to maintain. It is pulled out of the cylinder using a piece of cord. The flat rubber disk seal can easily be replaced by one cut from an old tyre inner tube.

Q12 "These jobs seem easy but in some areas villagers are not familiar with machines and even that level of maintenance may be too difficult. What would you do in that situation?"

"We have anticipated this and suggest that complete, fully assembled replacement valves are kept in reserve so that complete valves can be exchanged. If even this is thought to be too difficult, a complete spare piston rod could be held in reserve and used until a mechanic can visit the village to change the seals on the original piston."

Q13 "You mention that these pumps are available in kit form for local assembly; what particular skills would be needed if we wanted to assemble them ourselves?"

"Kits are available to any organisations or projects involved with water supply or irrigation as soon as a significant demand for the pumps can be shown to exist. The total manufacturing process involves a number of special skills, such as injection moulding of the valve components, welding and plastic forming but the kits will provide all the components fully worked and ready for final assembly.

Q14 "How much water can be pumped with the Rower Pump?"

"This depends on the lift from water level to the pump, the pump model and the strength of the pump operator. A healthy man can pump more than 5 m3/hour (1.4 lit/sec.) but women and children would usually pump less. The large diameter cylinder enables even a child pumping slowly to produce more water than from most other hand pumps; a pull of only 45 cm discharges 1.5 litres.

Q15 "How easily can children use the pumps?"

"At low lifts a single child can use the Rower Pump quite easily but at greater lifts 2 children can work together, each taking one side of the broad T-handle.

Q16 "How many Rower Pump models do you offer?" We have two standard pumps. The first has a 75mm pipe with 65 mm internal diameter cylinder which gives the best volume at low lifts (up to about 5.0m). The "2 inch" pump has a narrower cylinder so it discharges less water per stroke but it can be used to lift up to about 8 m. One further Rower Pump option has recently been developed. The Rower Pump Delivery Model has a solid plunger which draws water into the cylinder but then pushes it back through a separate discharge port at the bottom end ofthe pump. Water can therefore be delivered under pressure either into irrigation pipelines or into an elevated storage tank. This model was developed in Zambia during 1995 and when field trials are complete it will be available as an option.

Q17 "All you have said about the SWS Rower Pump is most interesting. Can you now summarise its advantages?"

"First, reliability. The SWS Rower Pump is made from high grade stainless steel and robust modern plastic. There is nothing to corrode, there is no pivot to wear and no end-stops to knock. The pump is buried within a mound of soil so it is very secure and resistant to theft or damage.

Second, high performance. Few other suction pump can lift as much water for as little effort as the SWS Rower Pump; this is the feature that most people comment on after trying it for the first time.

Third, easy maintenance. NO SPECIAL TOOLS ARE REQUIRED. New piston cup seals can be fitted within moments while easily replaceable rubber flap seals may be cut from old tyre inner tube.

The pump's light weight is also an advantage. Many pumps are too heavy to be economically air- freighted. An SWS Rower Pump, fully packed, weighs only 5 kilos which minimises the total cost. Currently the Rower Pump cost 125 (sterling) ex-factory while a complete package including pipework, fittings and filter is about 250 ex-factory or 275 delivery by air.

It is very important to remember that Rower Pumps are not intended for deep wells but are ideal for many situations which conventional deep well hand pumps are just not suited for. In situations where villagers depend on open water holes and low level springs SWS Rower Pumps have come into their own and are hard to beat.

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© 1997 SWS Filtration | Page maintained by RHC
Last updated 18.04.01 | Contact details
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