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The Pressure Tank: What It Does and How It Fails

Most well problems people blame on the pump are the tank, and the tank is the simpler half of the system to put right.

The short of it

The pressure tank is why the pump does not run every time a tap opens. It holds water under air pressure between a cut-in and a cut-out setting. When the bladder fails the cushion goes, the stored volume collapses, and the pump begins to cycle.

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What it is for

Without a tank, the pump would have to start every time anyone ran a tap. The tank holds water under pressure so small draws come out of storage, and the pump only runs when storage falls far enough to matter. It exists to protect the pump.

Cut-in and cut-out

Two pressures define the system. Cut-in is where the switch starts the pump; cut-out is where it stops. The gap between them is what gives the pump a rest, and a common pairing is a twenty-pound gap. The gauge on the tank should swing slowly between those two figures during normal use.

A gauge that swings quickly is short cycling. A gauge that never moves is not reading.

How a tank fails

Modern tanks separate air from water with a bladder or diaphragm. When that fails, air dissolves into the water and leaves with it, the tank waterlogs, and the storage disappears. Older galvanized tanks had no bladder at all and lost their air charge routinely, which is why they needed periodic recharging.

What that means for a quote

A contractor who diagnoses short cycling and quotes a pump has skipped the tank. Ask which one was tested and how. It is a fair question and the answer is quick.

On a well, nobody else is going to notice it failing.If the pressure has gone or the pump is cycling, that is worth a call today rather than next week. We route to contractors who work on wells specifically and cover your area, matched on the ZIP code you give, and you are never charged. Nor does it have to be the well; any plumbing work is routed the same way.

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