Hand pumps for water lifting
Practical Action
The reciprocating suction pump has the pump cylinder situated above ground or near the surface.
Pulling up the plunger lowers the atmospheric pressure in the cylinder (creates suction) causing
the atmospheric pressure outside the
cylinder to push the water upwards.
The main limitation of this pumping
method is that the atmospheric
pressure difference between the
inside and outside of the cylinder is
only large enough to raise water up to
a maximum of 7m from the water
table. If the shallow well is over
used, the level of the water-table
may fall as the underground water
reservoir is depleted. If the water
table level falls to a depth of greater
than 7 metres, the pump will no
longer work.
Figure 5: Shallow-well piston pump
The following section describes three
different types of reciprocating suction
pump used for raising water from
shallow-wells of up to 7 m in depth
i.e. the piston pump, the rower pump
and the treadle pump.
Shallow-well piston pump
Piston pumps, based on the same design shown in Figure 4, are relatively cheap and are widely
used as household hand pumps.
Traditional piston pumps have to be “primed” before use which means pouring water into the
cylinder so that the seal around the piston is airtight. It is very important that clean water is used
for priming, to avoid contamination of the pump and the spread of water-borne diseases.
More recent VLOM designed piston pumps using better suction valves have removed the need for
priming.
The shallow-well piston pump can be adapted to deliver water to a higher elevation than the pump
e.g. to a water storage tank or to deliver water under pressure to village water mains. This “force”
pump uses the same operating principle as the piston pump but the design is slightly altered so
that the top is airtight. This is done by putting a valve on the spout and adding a "trap tube" and
air chamber which maintains the pressure (and hence flow) during the up-stroke. Typical
elevations achieved using force suction pumps are between 5 – 10 metres.
Advantages
Relatively simple maintenance (main pump
components positioned above ground)
Large piston diameter gives fast water delivery
(24-36 litres/min at 7 m depth)
Disadvantages
Limited to wells of less than 7 metres in depth
Pump priming may cause water contamination.
Most designs have maximum usage of around
50 people/day
5