Pumps & Pressure Tanks

A pressure tank keeps water pressure at a constant level within the home. As water is pumped from the well into the pressure tank, the air in the tank is compressed until it reaches a preset level, generally 40 to 60 pounds per square inch (psi).

A pressure tank is important because it keeps water pressure at a constant level. It also keeps the water and air separated. Without these features, the water pump would turn on and off quickly – a problem caused by cycling – which can quickly burn out the pump motor.

After a well is drilled, a water pump is installed along the well casing to push or lift water from below the ground into your home. It is placed below the water level within the well so that it will not be affected by any water drawdown or periods of drought.

The size of this pump is determined by the size of your home, the number of plumbing fixtures, and peak water demands. A typical water pump for domestic use can usually pump 10 gallons per minute out of the well using a ½ horsepower motor. Some homes that use a significant amount of water for irrigation, a home business or feeding animals may need a larger pump.

Jet pumps, which can be located above ground, are sometimes used in shallow wells that are 4 inches in diameter or less. But submersible pumps are most often used in wells today and is likely the type of pump in your home. Submersible pumps know when to turn on when the pressure within the home’s water system drops below a certain level

As water is pumped from the well into the pressure tank, it compresses the air in the tank until it reaches a preset level, typically the 40 to 60 pounds per square inch (psi). When someone turns on a faucet, air pressure in the tank forces water throughout the plumbing until the pressure drops to the preset trigger pressure, usually the 20 to 40 psi. That tells the water pump to turn on, and water is then drawn into the house and tank. When the faucet is shut off, pressure builds until it is restored to its default shut-off level. The amount of water delivered by the pressure tank between the time the pump shuts down and the time it starts again is called the drawdown.

Pressure tank size and the drawdown will depend on the amount of water the pump can draw into the home in 1 to 2 minutes. Some tanks hold as little as 10 gallons, others more than 200 gallons. The most common size of pressure tanks in residential homes hold about 44 gallons and have a drawdown of about 16 gallons. If your home uses more than the average amount of water or has a well with a low yield, a larger pressure tank may be needed.