Water Pressure Tanks

How Water Pressure Tanks Work in Supplying Your Home’s Water Needs

By Mark J. Donovan




If your home gets its water supply from a private well, then located in your basement or utility room, near where the water pipe comes in from the well, is a large metal tank known as a water pressure tank

Purpose of Water Pressure Tanks

Water pressure tanks work in conjunction with private wells to supply water to your home. Water pressure tanks serve three key functions. First, they provide a constant water pressure to your home’s water supply system. Second, they help protect and prolong the life of the submersible well pump that sits in your well. Third they act as a reservoir for holding water.

How Do Water Pressure Tanks Work

A water pressure tank is a large steel tank that contains a rubber diaphragm in it that separates the pressure tank into two sections. The upper section of the tank is filled with air. As water feeds into the bottom of the tank the rubber diagram is forced upwards toward the top of the tank and compresses the air.

The result is a pressurized holding tank of water. Via a pressure switch hanging off of the pressure tank and the well pump, the pressure in the tank is kept constant between a range of 20 and 60 pounds per square inch, or PSI.
So for example, when someone turns on a water faucet in the home the water pressure tank supplies a relative constant water pressure to the faucet.When the tank pressure eventually drops to a level of around 20-30 psi a signal is sent to the submersible well pump to turn on and replenish the water in the pressure tank.
Water pressure tank

When the tank pressure reaches around 40-60 psi, a signal is sent to the submersible well pump to shut off. As a result a relatively constant water pressure is maintained in the home’s water supply system. In addition, with a water pressure tank, the submersible well pump does not need to turn on every time a faucet is turned on in the house, thus prolonging the life of the well pump. A well pump’s life is directly proportional to the number of times it is switched on and off.

When Shopping for a New Water Pressure Tank

Over time the water pressure tank will fail. It is either caused by the loss of air pressure in the upper half of the tank, or the diaphragm has failed. You can tell if this is the case by tapping on the tank. If it sounds hollow at the top and like a dull thud on the bottom, then the tank is most likely okay. On the other hand, if the tank sounds like a dull thud both at the top and bottom then chances are the diaphragm has failed and a new pressure tank is required.

When shopping for a new pressure tank it is important to know the number of plumbing fixtures in your home and the gallons per hour flow rate of the well pump.


With this information you can look at a pressure tank manufacturer’s buying guide to determine the right tank for your specific home’s needs. Note, however it is always better to go bigger when buying a pressure tank as this will reduce the number of on/off cycle times of the submersible well pump.


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