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Handpumps

No change in size, 04:33, 24 September 2013
Handpump types
'''Suction pumps'''<br>
[[Image:rower pump.jpg|thumb|right|250px200px| The Rower Pump is a suction pump in which the piston is directly activated. Photo: [http://www.rural-water-supply.net/en/implementation/handpump-overview/rower-pump RWSN.]]]
In a suction pump, the cylinder is above the water table, usually near the top of the pump head. The rising main extends below the water table. When the pump is operated, during the upwards stroke it appears that water gets “sucked up” through the rising main into the cylinder. In fact, the atmospheric pressure forces the water into the area of low pressure underneath the piston. The theoretical limit to which the atmospheric pressure can push up water is 10 metres (m). In practice, suction pumps can be used to lift water up to about 7 or 8 m.
'''Direct Action handpump'''<br>
[[Image:DirectActionHandpump.jpg|thumb|right|250px200px| Direct action handpump mechanics. Drawing: WHO.]]
Direct action handpumps are usually made of PVC and other plastics, and are installed on boreholes of limited depth. A plunger is attached to the lower end of a pump rod, beneath the groundwater level. The user moves the pump rod in an up-and-down motion, using a T-bar handle. On the up-stroke, the plunger lifts water into the rising main, and replacement water is drawn into the cylinder through the foot valve. On the downstroke, the foot valve closes, and water passes through a one-way valve in the plunger and is lifted on the next upstroke.
'''Lever Action handpump'''<br>
[[Image:bush pump.jpg|thumb|right|250px200px|The Bush pump is a lever action pump that can handle heavier usage by many people. Photo: [http://www.rural-water-supply.net/en/implementation/handpump-overview/bush-pump RWSN.]]]
Most deep-well handpumps are of the lever action type. The increased length of the water column in deep boreholes requires more effort to draw water and the lever of the handle makes the operation easier. Besides the conventional handle, there are also pump designs, which use a flywheel to operate a crankshaft for transforming the rotation into an up-and-down movement.
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