Well Pressure Tank Problems

How the tank is supposed to work

Inside a modern tank, a rubber bladder or diaphragm separates the water from a cushion of compressed air. The pump fills the water side until the pressure switch hits its cut-out, then shuts off, and the squeezed air pushes water to your taps while the pump rests. When that air cushion shrinks or the bladder fails, there's nothing left to push. The pump has to start nearly every time someone opens a tap.

That matters because starts are what wear a pump out. Franklin Electric lists a waterlogged tank as one of the causes of a motor that starts too often.

Symptoms and what they usually mean

Checks you can do yourself

Work through these in order. The first two take a minute and tell you a lot.

Knock on it

HomeGuide's quick test is to tap the tank: a waterlogged tank sounds solid rather than hollow. Knock near the top and near the bottom. A healthy tank sounds different at the two spots because the top holds air.

Press the air valve

The air valve on top looks like a tire valve. Angi's method is to press the valve core gently with the tip of a screwdriver. Air should hiss out. If water comes out, the tank is full of water, and on a bladder or diaphragm tank that means the membrane has a hole. Stop there, because no amount of air will fix it.

Check the pre-charge properly

If only air comes out, measure the charge. This is the test that settles most arguments about a tank.

1. Turn off the pump breaker.
2. Hook a garden hose to the tank's drain valve and drain it to a floor drain or bucket. Opening a couple of faucets speeds it up.
3. When the water stops and the plumbing gauge reads zero, read the air valve with a tire gauge.
4. Compare the reading to your pressure switch. Amtrol says to set the pre-charge 2 psi below the cut-in pressure, for example 38 psi on a 40/60 switch. Angi gives the same rule, 28 psi for a 30/50 setup.
5. Make any adjustment only while the tank is empty, the system is off, and the tank is at room temperature.

One catch. Amtrol's manual says not to adjust or add pressure if there has been a loss of air, and warns that lost tank air pressure may indicate internal corrosion. So a big shortfall points toward replacement, not a refill.

Rule out the rest of the system

If the pre-charge is right and the pump still short cycles, the tank may be innocent. Goulds lists a defective foot valve or suction check valve, a waterlogged tank, a pump set more than 5 feet from the tank, and high-friction valves between pump and tank as causes of excessive cycling. Franklin adds a bad or misadjusted pressure switch, a check valve stuck open and leaks anywhere in the system. Our pressure switch troubleshooting page covers the switch side.

Pressure tank leaking from the bottom

Water under a tank comes from one of two places: the fitting where the tank meets the plumbing, or the steel shell itself. Dry everything off and watch. A drip at the tank tee or drain valve is a plumbing fix. A weep from a seam or a rusty spot on the shell is not.

HomeGuide treats visible corrosion on the outside as a sign of deterioration inside, and Amtrol says a tank that looks like it's malfunctioning or shows corrosion needs a licensed professional right away. If the tank sits where a leak would damage floors or finishes, Amtrol calls for a drip pan piped to a drain.

Can a bladder tank be repaired?

HomeGuide notes that bladder tanks use a replaceable bladder. Whether yours can be rebuilt depends on the model, so check the label or manual before you buy parts. Many homeowner tanks are sealed units, and on those a failed diaphragm means a new tank. Older galvanized air-over-water tanks have no bladder at all. HomeGuide says they need more upkeep because the air slowly dissolves into the water, which is why they waterlog. Our waterlogged pressure tank page explains how to recharge one.

Pressure tank maintenance

There isn't much to it, which is why tanks get ignored until they fail.

• Have the whole system, tank included, checked by a licensed professional every year, and more often as it ages, as Amtrol recommends.
• Check the pre-charge with the tank drained whenever the pump starts cycling faster than it used to. Amtrol notes that shorter pump cycles can come from lost tank air.
• Keep the tank out of direct sun, away from freezing, and out of spaces that top 130°F.
• Expect a tank to last 10 to 15 years, less with hard water or heavy minerals, according to HomeGuide.

The drain valve on many tanks is a cheap boiler drain that drips once it's been opened a few times. Have a spare and a roll of thread sealant on hand before you start.

Repair or replace, and what it costs

Replace the tank when the bladder has failed, the shell is rusting or leaking, or it keeps losing its charge. HomeGuide puts the cost to replace a well pressure tank at $800 to $1,500 including the tank and labor, with labor alone at $250 to $500 or more.

Angi's DIY guide puts a new tank at around $400 on average, with $125 to $200 for labor if you hire it out. Prices climb if the pressure switch, gauge or pump also need replacing. For the full job, see pressure tank replacement and pressure tank cost.

Call a well contractor if the tank is leaking from the shell, if water comes out of the air valve and you'd rather not swap a heavy tank yourself, or if the pump keeps short cycling after the charge checks out.