For a shallow-well piston pump with pressure tank, a shallow-well float-type control will be needed.
When the water level in the pressure tank gets too high, the float
riding on the water surface inside the tank is high enough to open the
air valve in the control. This allows the pump to draw outside air into the
air-control volume, past the air valve and into the tube that connects to the
suction side of the pump. From there it is drawn into the pump where it
mixes with the water into the pressure tank. The air then separates from the
water and rises to the top of the tank.
As air accumulates in the tank the water level lowers due to the
increasing pressure. The float rides at a lower position, and a point is
finally reached where the float will not open the air valve at any time
during the pumping period. This shuts off air to the pump until the water
level in the tank rises high enough to again open the valve.
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