It should be noted that much of the system sizing information in this section is related to the source of water supply; namely, whether it is an adequate capacity groundwater source, a limited capacity groundwater source, or a surface water source. Certainly any distribution system must also be related to pump capacity (rate), tank capacity, and recommended water pressures.

Water System Components and Operation

A water system consists of a pump, a storage tank, and accessories needed to operate the system automatically. One arrangement is shown schematically in Fig. 6.

The pump may be one of several types: Shallow-well or deep-well and jet, submersible or reciprocating. Basically, the pump delivers the water from the well or other water source to a tank where it is held under pressure. Section (a) of Fig. 6 shows a typical shallow-well jet pump. (The term "Pump" usually refers to both the pump itself and an electric motor which together make up the pumping unit. A gasoline engine could be used, but the almost universal availability of electric power makes this the usual energy source.)

To make the system automatic, a storage system in the form of a hydropneumatic tank is used. Section (b) shows this part of the system. The pump delivers water under pressure to the tank. As the tank fills, air over the water is compressed. If no water is being used, delivery to the tank continues until the pressure reaches a set level, usually 40-50 psi. A pressure switch then opens the electrical circuit and the pump stops.

When a valve is opened in the system, air pressure in the upper part of the tank forces the water to flow. The pressure falls as the water flows out of the tank. When it drops to the cut-in setting of the pressure switch, the latter closes the circuit and the pump starts. A cycle is thus completed.