The pump discharge line must be connected to a storage tank. The tank, also called a pressure tank, is generally located on the lower level of the house but might also be located in an outside pump house. Water from the tank is forced into the house supply pipe whenever there is a demand at one of the plumbing fixtures. A properly functioning tank provides a water reservoir that balances the capacity of the pump against the usage demand. It prevents excessive short-cycling (too rapid starting and stopping), which can cause switch and motor trouble.
The water in the storage tank is under pressure. Since water cannot be compressed, the tank must be partially filled with air to function properly. Over time, the water in the tank absorbs the air, so that the tank eventually becomes completely filled with water. The tank is then “waterlogged,” and the pump performs as if no tank were used. Any small request for water, such as filling a glass, will cause the pump to cycle rapidly. This in turn will cause premature wear on the pump, motor, and switch.
The pressure range normally used for well-pumping systems is between 20 to 40 or 30 to 50 pounds per square inch (psi). If a waterlogged condition exists and there is a demand for water, you will hear the pump starting and stopping rapidly if the pump is the jet or piston type. However, when a submersible pump is used, you will not hear the pump. In this case, you can tell that a waterlogged condition exists because the pressure switch will be clicking on and off. Also, the pointer on the pressure gauge will be fluctuating between the high- and low-pressure limits. If you find a waterlogged tank during your inspection, record it on your worksheet. The condition can be easily corrected by draining and then injecting air into the tank.
Fig. 13-12. Typical submersible pump installation. Only the controls and storage tank are visible, since the pump is Well located in the well. seal
|Motor control box Fused disconnect switch Pressure switch Pressure gauge Storage tank Tee Air valve Special check valve Well vent||To house|
Some pumping systems have an air-charger apparatus that introduces air into the tank with each cycle to avoid waterlogging. Some prepressurized tanks claim to achieve a permanent separation of air and water by means of a plastic or rubber diaphragm or bag. These tanks should also be checked to determine whether they are waterlogged. I have found that on occasion they are, a condition that indicates a faulty diaphragm or bag.
In most areas of the country, the storage tank should be insulated to prevent condensation during the summer. Some tanks show signs of deterioration because of excessive rusting, a condition brought about over the years by moisture condensation on the tank. Depending on the degree of deterioration, the tank might have to be replaced or scraped, repainted, and insulated.
Pressure switch and gauge
All systems must have a pressure switch and pressure gauge. The switch automatically starts and stops the pump at predetermined pressures. The pressure differential between start and stop is usually about 20 psi. The normal pressure range, as mentioned earlier, is 20–40 psi or 30–50 psi, sometimes 40–60 psi. Pressure in excess of 65 psi is abnormal and should be checked out by a pump service company. It might be caused by a faulty pressure switch.
The switch can easily be checked by turning on a faucet. Look at the pressure gauge and watch the pressure drop until the pump is activated by the low limit. Have someone turn off the faucet while you watch the pressure building up on the pressure gauge. When the upper limit is reached, the pump should stop. If it does not or it cuts out at too high a pressure, there is a problem. If the pressure gauge is broken, this test cannot be performed. All too often, I have found inoperative pressure gauges. If you find one, it should be replaced.
Standard tanks are normally rated for a maximum pressure of 75 psi. As a precautionary measure, there should be an automatic relief valve on the storage tank or associated piping. The relief valve will prevent problems associated with excessive pressure buildup if the pressure switch malfunctions and allows the pump to continue running.
Look at the pressure gauge to see if the system will hold pressure when the pump is not running and no water is being used. If the pointer on the gauge drops, it indicates a leak. If no signs of leaks were noted during the plumbing inspection, the leak is probably between the storage tank and the well. Note this item on your worksheet, for it must be corrected.