CEMP-E
TI 814-01
3 August 1998
impermeable boundary because little or no recharge is obtained from the direction of the
impermeable boundary.
(2) Location. Where a source of recharge such as a stream, exists near the proposed
well field, the best location for the wells is spaced out along a line as close as practicable to
and roughly parallel to the stream. On the other hand, multiple water supply wells should be
located parallel to and as far as possible from an impermeable boundary. Where the field is
located over a buried valley, the wells should be located along and as close to the valley's
center as possible. In hard rock country, wells are best located along fault zones and
lineaments in the landscape where recharge is greatest. These are often visible using aerial
photographs. Special care should be exercised to avoid contamination in these terrains since
natural filtration is limited.
j. Pumps. Many types of well pumps are on the market to suit the wide variety of capacity
requirements, depth to water and power source. Electric power is used for the majority of
pumping installations. Where power failure would be serious, the design should permit at least
one pump to be driven by an auxiliary engine, usually gasoline, diesel or propane. The most
appropriate type is dictated by many factors for each specific well. Factors that should be
considered for installation are:
- capacity of well
- power source
- capacity of system
- standby equipment
- size of well
- well drawdown
- depth of water
- total dynamic head
- type of well
(1) Type. There are several types of well pumps. The most common are line shaft
turbine, submersible turbine, or jet pumps. The first two operate on exactly the same principal.
The difference being where the motor is located. Line shaft turbine pumps have the motor
mounted above the waterline of the wel and submersible turbine pumps have the motor
mounted below the water line of the well. Jet pumps operate on the principal of suction lift. A
vacuum is created sufficient to "pull" water from the well. This type of pump is limited to wells
where the water line is generally no more than 8 m (25 ft) below the pump suction. It also has
small capacity capability.
(2) Choice. Domestic systems commonly employ jet pumps or small submersible
turbine pumps for lifts under 8 m (25 ft). For deeper wells with high capacity requirements,
submersible or line shaft turbine pumps are usually used and are driven by electric motors. A
number of pump bowls may be mounted in series, one above the other to provide the
necessary discharge pressure. Characteristics for various types of pumps used in wells are
listed in table 5-5.
5-21
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