How long a well pressure tank lasts: 10–15 years

What the lifespan figure rests on

We found no agency or extension service that publishes a lifespan for well pressure tanks. The 10 to 15 year figure comes from Mid Atlantic Water, which sells tanks, and its author reports seeing Well-X-Trols last 30 to 40 years. Treat it as a rule of thumb. The firmer numbers are the warranties: Amtrol lists a three year limited warranty on its diaphragm, full acceptance and partial acceptance designs, and Pentair covers its Wellmate WM01 and WM02 inline tanks for five years.

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What shortens it

Mid Atlantic Water names three causes: acidic water with a pH below 6.5, sediment, and a tank too small for the pump, which makes the pump cycle constantly. EPA's secondary standard for pH is 6.5 to 8.5, so a routine pH test tells you whether the first one applies.

A tank that is too small also wears the pump. Franklin Electric warns that rapid cycling can damage motor splines and bearings and overheat the motor.

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Signs the tank is failing

A waterlogged tank has lost its air charge, so it stores little water and the pump starts every time a tap opens. The Driller describes how to check: with the water side of the tank completely empty, the air charge should read about 2 psi below the pressure switch cut-in. If the tank will not hold that charge, or water comes out of the air valve, the diaphragm or bladder has failed.

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