What the pressure tank does
A well pump pushes water into a pressure tank. The tank holds a cushion of air that squeezes the water and keeps pressure steady. Because the tank stores some water under pressure, the pump doesn't have to start every time you open a faucet or flush a toilet. It runs, fills the tank, and rests.
Most newer tanks keep the air and the water apart with a rubber bladder or diaphragm. The air side is filled at the factory and has its own air valve on top. The water side connects to your plumbing.
Signs the tank is the problem
- Rapid cycling. The pump clicks on and off every few seconds. Frequent on-and-off cycling is a reason to call a professional, according to the National Ground Water Association.
- Sputtering or spitting taps. Air and water arrive in bursts.
- Pressure that swings. Strong, then weak, then strong.
- A waterlogged tank. The tank has lost its air cushion and is mostly full of water. The pump has almost nothing to push against, so it cycles fast.
A bad pressure switch can look the same. So can a leak in the plumbing. The well pump not working guide gives the order to check things in, and well pump repair and replacement covers the pump itself.
Check the air charge, or replace the tank?
The air charge is the air pressure in the tank when no water pressure is on it. Flotec's owner's manual for its pre-charged tanks says to set or check the charge with no water in the tank and no water pressure in the system. Turn the pump off, open a faucet until the pressure is gone, then read the air valve with a tire gauge.
The manual's chart sets the tank's air charge a little below the pressure at which the pump switches on. For a pump switch set at 20 psi on and 40 psi off, the chart calls for 18 psi in the tank. Your tank's label and manual have the right number for your system. The manual also says to check the air charge once a year, and to put the valve cap back on, because a missing cap can let air out and lead to a waterlogged tank and a failed bladder.
What that means in practice:
- Low air, tank still sound. A plumber or pump installer may be able to restore the charge. This is a quick job.
- Air keeps disappearing. The bladder or tank is probably failing. Adding air only buys time.
- Water comes out of the air valve. Flotec's manual describes this as a bladder leak. On a tank like that, the fix is a new bladder or, more often, a new tank.
Bladder tanks and older tanks
Older systems often use a plain steel tank with no bladder, where air and water touch. The air slowly dissolves into the water, so the tank needs air added back from time to time. Manufacturers' manuals still describe both types, and they give different settings for the pressure relief valve on each, which is one reason to let a pro handle the swap.
A tank that is rusting through, leaking at a seam, or soaked at the base should be replaced. Don't wait for it to fail on a cold night.
Sizing, in general terms
A bigger tank holds more usable water between pump starts, so the pump runs longer and rests longer. A tank that is too small makes the pump cycle more often. The right size depends on the pump's flow rate, the switch settings and how much water the house uses. A plumber or pump installer can match those. Don't size one by guessing from the shape of the old tank.
Wells outside the city
Many homes in rural Washington, Carter and Sullivan counties are on private wells. If yours is one, you own the whole system: well, pump, tank, switch and the pipe to the house. The EPA advises testing a private well every year for total coliform bacteria, nitrates, total dissolved solids and pH, and testing again after flooding or when the water's taste, color or smell changes. Its private well guidance says to contact your local or state health department for advice on testing. The National Ground Water Association recommends a professional well inspection every year, and says pumps often wear out before the well does.
Before you call
Note what you hear and see: how often the pump starts, whether the gauge needle jumps, and whether the problem is worse when two taps run. Say you're on a well when you call.
Stay safe
Pump wiring carries voltage that can injure or kill. One pump maker's manual labels it "hazardous voltage" and says to disconnect power before installing or servicing. Turn off the breaker before you touch anything near the switch or the pump wiring. Never open or cut a tank that still has pressure on it.