Waterlogged Well Pressure Tank

What waterlogged means

A well tank stores water under a cushion of compressed air. In a bladder or diaphragm tank, a rubber membrane keeps the two apart. In an older air-over-water tank, the air sits right on top of the water.

As the pump fills the tank, the air compresses. When you open a tap, that compressed air pushes water out while the pump stays off. Lose the air and the tank becomes a steel pipe full of water with no spring in it. Pressure collapses the moment you draw water, and the pressure switch calls the pump right away.

Signs your tank is waterlogged

• The pump clicks on within seconds of opening a faucet, and clicks off soon after you close it.
• The pressure gauge needle bounces quickly between cut-in and cut-out.
• Water pressure surges and drops while you shower.
• The tank sounds solid all the way up when you knock on it, instead of hollow near the top.
• On a bladder tank, water comes out when you press the air valve on top.

What causes it

Air leaking from a bladder tank. The air charge in a bladder tank slowly leaks out through the valve or seals over the years. Amtrol notes that shorter pump cycles can come from lost tank air pressure.

A torn bladder or diaphragm. Once the membrane splits, water floods the air side. This is the end of the tank.

Air dissolving in an air-over-water tank. With no membrane, the air slowly dissolves into the water, which is why HomeGuide says these tanks need more maintenance. Many have an air volume control on the side meant to stop this. When that fitting fails, the tank waterlogs over and over.

A wrong pre-charge from the start. If the air charge was never set to match the pressure switch, the tank holds less water than it should and acts waterlogged even with an intact bladder.

Why you shouldn't live with it

Every faucet opening becomes a pump start, and starts wear out pumps, switches and control boxes. Franklin Electric rates its single-phase submersible motors up to 3/4 hp for 300 starts a day, and its 1 to 5.5 hp single-phase motors for 100. The manual also says a motor should run at least one minute each time to shed the heat from starting. A waterlogged tank breaks both rules all day long. Goulds lists a waterlogged tank among the causes of a jet pump that cycles too much.

The pressure switch contacts take a beating too, since they arc on every start. A switch that's chattered for months is worth replacing along with the fix.

How to confirm it with a tire gauge

1. Turn off the pump breaker.
2. Connect a hose to the drain valve at the bottom of the tank and drain it to a floor drain. Open a couple of faucets to speed it up.
3. When the water stops and the plumbing gauge reads zero, press a tire gauge onto the air valve on top of the tank.
4. Compare the reading to your cut-in pressure. It should be 2 psi below cut-in. On a 30/50 switch that's 28 psi, and on a 40/60 switch it's 38 psi.

If the gauge reads near zero, or water comes out of the valve, you've found the problem.

How to fix a waterlogged pressure tank

Bladder or diaphragm tank that only lost air

Read the tank's own manual before you add air. Amtrol's Well-X-Trol manual says not to adjust or add pressure if there has been a loss of air, and to call a licensed professional if the tank appears to be malfunctioning. Where a tank maker does allow a pre-charge adjustment, Amtrol's rule is to make it only with the tank empty of water, the system off and the tank at ambient temperature.

If you aren't sure the tank can safely be recharged, treat a tank that lost its air as a replacement job and have a well contractor look at it.

Bladder tank with water at the air valve

Replace the tank. The membrane is torn, and adding air just pushes it out through the hole. See pressure tank replacement for the swap.

Galvanized air-over-water tank

Drain the tank completely so air can get back in, then close the drain and let the pump refill it. That restores the cushion. If it waterlogs again within days or weeks, have the air volume control checked, or consider swapping to a bladder tank.

How to drain a waterlogged pressure tank

Power off first. Attach a garden hose to the drain valve at the base, run it to a floor drain or outside, and open the valve. Opening a couple of faucets lets air in and speeds the flow. When nothing more comes out and the gauge reads zero, the tank is empty. If you're recharging a bladder tank, keep the faucets open and the power off until the air is set.

Recharge or replace

Recharge only when the tank maker's instructions allow it, the bladder is intact and the tank holds its charge afterward. Replace when water comes out of the air valve, the shell is rusting, or the charge keeps leaking away. HomeGuide puts well pressure tank life at 10 to 15 years, so an old tank that waterlogs is near the end anyway.

HomeGuide's range for replacing a well pressure tank is $800 to $1,500 with labor. Angi's figure for the tank alone is around $400 on average. More on pressure tank cost.