Hand pumps for water lifting
Practical Action
Advantages
Relatively cheap, and easy to manufacture (for
wells down to 35 m rope pumps are five times
cheaper than piston lift pumps.)
Maintenance uses local skills and materials
Disadvantages
Operation limited to depths of up to 35 m.
Initial water delivery is relatively slow at
greater depths.
Water contamination possible because well is
not totally sealed.
Frequent simple maintenance required
Diaphragm pump
The diaphragm pump is a deep-well pump which can operate at depths of up to 70 metres. The
diaphragm pump delivers 25 litres/ min at 45 metres depth.
Figure 10: Diaphragm pump
The flexible diaphragm is situated
inside a cylindrical pump body at the
bottom of the well. The pump
operates by the expansion and
contraction of the flexible diaphragm
which forms one wall of a closed
chamber. The diaphragm is expanded
and contracted using a secondary
piston pump, which in turn is moved
by a foot pedal or hand lever.
The closed chamber has an inlet and outlet valve. On the contraction of the diaphragm the inlet
valve opens to draw water into the closed chamber and the outlet valve closes. When the
diaphragm is expanded the inlet valve closes and the outlet valve opens to pump water up a
flexible rising main.
The main disadvantage of this pump is that replacement diaphragms are required at relatively
short intervals. These diaphragms are expensive and can make the maintenance costs of this
pump prohibitive for many village water management organisations. In addition, this type of pump
is not suitable for water with sediment or sand particles in it since these will lead to pump
breakdown.
Advantages
Suitable for deep well applications up to 70
metres in depth.
Several pumps can be installed in the same
well or borehole.
Maintenance facilitated by easy access to main
wearing parts in the upper cylinder.
Disadvantages
Relatively expensive to manufacture.
Replacement diaphragms expensive and
required at short intervals.
Not suitable for water with sediment or sand
particles which damage the pump.
Helical rotor (or "progressive cavity") pump
The helical rotor pump is a rotary pump which can lift water from depths of up to 100 metres.
Typical water yields at 45 metres are around 16 litres/ min. Instead of a piston, the helical rotor
pump has a metal "rotor" which has a corkscrew shape and which turns inside a rubber "stator" or
sleeve (see Figure 8B). There is a continuous seal between the two parts of the pump and the
turning action forces the water upwards. Instead of a pump lever there is one or two turning
handles. The faster the handles are turned the more water is obtained from the well.
The pump is relatively reliable. Nevertheless a key disadvantage is that pump maintenance
requires that the whole pump be lifted and dismantled using specialist equipment and hence it is
not suitable for maintenance by a village level organisation.
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