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How To Design And Install Plumbing
The building supply main is connected to the delivery side of the pump, between the check valves and the tank. A valve (C) may be placed on this connection.
It is advisable to install a valved by-pass between the city mam and the building supply main. In case of pump failure, this valve (D) can be opened and a part of the building will be supplied with water.
The air compressor (E) is also connected to the underside of the tank. This line must be equipped with a valve and a check valve.
The electric control switch is located conveniently, and is connected to the tank with a pipe of small diameter. The varying pressures within the tank affect the mechanism of the control devices which start and stop the pumps, F.
It is absolutely essential that all connections be made on the underside of the storage tank.
Operation of an Air Pressure System. The operating principle of an air pressure system is not difficult to understand. It is based OP known facts of physics. The tank, being air-tight, serves as an air chamber. When water is forced into it the pressure of air is increased in proportion to the volume of water. Air is elastic or compressible, and water is inelastic or non-compressible. As the air is squeezed into less space, a pressure greater than that of the atmosphere is exerted on the surface of the water. Example: The tank is originally under atmospheric pressure of approximately 14.72 pounds at sea level. Atmospheric pressure under these conditions will not act as an elevating agent. This is because the same pressure exists on all sides of the confined liquid. A gauge installed on the vessel will indicate zero Pounds pressure.
When water is forced into a closed vessel that is under atmospheric pressure to the extent of one half its cubical content, a gauge installed on the tank will indicate about 15 pounds. This represents 15 pounds of pressure above atmospheric, Fig. 216A, and it will elevate water, theoretically, 34.6 feet. Should more water be pumped into the tank to the extent of two-thirds its content, a pressure of approximately 30 pounds will be indicated on the gauge,
If water is pumped into the tank to three quarters of its content, approximately 45 pounds will be indicated on the gauge, Fig. 216B. Theoretically, this will elevate the water 103.9 feet.
