Why Does My Well Pump Keep Running or Short Cycling?

A healthy well pump runs in steady cycles: it starts when pressure drops to the switch’s cut-in setting, runs until it reaches cut-out, and shuts off. Two common problems break that pattern. Either the pump won’t stop running, or it starts and stops far too often, which is called short cycling. They have different causes, so it helps to know which one you have.

Not sure? The Well Pump Problem Troubleshooter can help you sort it out.

Short cycling: on, off, on, off

Short cycling usually sounds like rapid clicking at the pressure switch while water is running, with pressure swinging up and down at the faucet.

Common causes

• The pressure tank has lost its air charge. This is the most common cause. Without its air cushion, the tank holds almost no usable water, so the pump has to start almost every time a faucet opens.
• A failed bladder or diaphragm. If water comes out of the air valve on top of the tank, the bladder has likely failed.
• A leaking check valve or plumbing leak. If the pump starts on its own when no one is using water, pressure is bleeding off somewhere.
• A pressure switch problem. A clogged inlet tube or worn switch can cause erratic on/off behavior.
• An undersized tank for the pump’s flow rate.

Why it matters

Every start is hard on a pump motor and the switch contacts. Amtrol lists rapid pump cycling as a sign a tank needs replacing, and frequent cycling is widely cited as a reason pumps fail early. Fixing a $500 tank problem can protect a much more expensive pump.

A pump that keeps running

If the pump runs long after the faucets are off, or never shuts off at all, look for these causes:

• A leak. A running toilet, dripping fixture, or broken buried line keeps pulling pressure down.
• A broken drop pipe or coupling down in the well, letting water fall back as fast as the pump lifts it.
• A worn pump that can no longer reach the cut-out pressure.
• A low water level. If the well can’t keep up, the pump may suck air and never build pressure.
• A stuck or misadjusted pressure switch that never opens, even when pressure is reached.

Safe checks you can make

1. Turn off all water and listen for running toilets or dripping faucets.
2. Watch the pressure gauge. Does it climb to the cut-out pressure, and how fast does it drop?
3. Walk the line from the well to the house and look for soggy ground.
4. Listen at the switch for rapid clicking while one faucet runs.
5. If you’re comfortable, check the tank’s air charge with the breaker off and the system drained to zero. Amtrol recommends a pre-charge about 2 psi below the cut-in pressure.

Leave anything involving the pressure switch internals, control box, wiring, or well cap to a professional. Well pump circuits typically carry 240 volts.

When to call

• The pump starts by itself with no water in use
• Water comes out of the tank’s air valve
• The pump never shuts off, or the gauge won’t reach cut-out pressure
• Your electric bill jumped without explanation