How Does a Pressure Tank Work?
Some buildings have their water supplied by a private well system. These systems feature pressure tanks which supply water to plumbing fixtures located throughout the building. Air pressure that is maintained in the tank has several purposes. It helps prevent water from surging out of faucets, and shower heads. It also prevents the pump from burning out due to overuse, acts as a spring to drive water out of the tank and maintains water pressure throughout the piping system. There are two types of compression tanks: steel tanks and diaphragm tanks.
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Plain Steel Tanks
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A plain compressed steel tank doesn't contain any moving parts. When the tank is first filled with cold water, the ratio in the tank is about 2/3 water and 1/3 air. When water in the piping system expands (and takes up more space), the water that the pipes can't hold anymore spills over into the tank, where it puts the air in the tank under more pressure. The newly-compressed air creates an increase in pressure in the piping system. The pressure is created by the increase in the temperature of the water; the warmer the water, the more it expands, and the more pressure it creates.
Diaphragm Tanks
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Diaphragm tanks serve the same purpose as enclosed steel tanks, but work in a different way. Diaphragm tanks, which are usually smaller than steel compression tanks, use a rubber diaphragm to keep air, and water in the tank separate. One side of the diaphragm is pre-charged with compressed air, causing the diaphragm to fully expand in the tank. When the tank is connected to the system, and water is pumped in, the pressure created by the influx of water presses against the diaphragm, compressing it. This keeps water pressure up throughout the system.
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