Well pumps · troubleshooting

Well pump short cycling: causes and fixes

Short cycling means your well pump turns on and off rapidly — every few seconds or minutes — instead of running in longer, steady cycles. It is one of the most common well-system complaints, and it shortens pump and pressure-switch life. Most causes live in the pressure tank, the switch, or a check valve. Here is a triage order that starts with the cheap, likely problems.

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Signs your pump is short cycling

• The pressure gauge swings between cut-in and cut-out in seconds while a faucet runs.
• You hear the pressure switch click on and off repeatedly.
• Water pressure surges and drops in the shower.
• The pump kicks on when nobody is using water.

Triage order: most likely to least likely

1. Waterlogged or wrongly charged pressure tank. With power off and the system drained, check the air valve on the tank. The usual target is about 2 psi below the switch’s cut-in pressure. If water comes out of the air valve, the bladder has failed and the tank needs replacing. Full how-to: pressure tank precharge.
2. Tank too small for the pump. An undersized tank gives the pump a short drawdown, so it cycles more. This is common after a pump upgrade. A well contractor can match tank drawdown to pump flow.
3. Clogged pressure switch port. The small tube or nipple under the switch can fill with sediment or scale, so the switch sees false pressure. Clean or replace the nipple. See replacing a 40/60 pressure switch.
4. Worn or mis-set pressure switch. Burned contacts or a switch whose differential has drifted narrow can chatter. Replacing it is inexpensive.
5. Leak in the system. A running toilet, a dripping outdoor spigot, or a leak in the buried line lets pressure bleed off, so the pump restarts with no faucet open. Shut every fixture and watch the gauge — if it falls, you have a leak.
6. Failing check valve. If the check valve in the well or at the tank leaks back, pressure drops right after the pump stops. Down-well check valves are contractor work.
7. Pump or control problems. A failing motor, a bad control box, or a dry-running well can trip protection repeatedly. Constant-pressure pumps such as the Grundfos SQE behave differently — they modulate speed instead of cycling. See SQ vs SQE.

Quick check you can do yourself

1. Note the cut-in and cut-out pressures on the gauge while running a faucet.
2. Turn off power to the pump, open a faucet, and drain the system to zero.
3. Check tank precharge with a tire gauge at the air valve. Set it to about 2 psi below cut-in.
4. Restore power and time a full cycle with one faucet open. Longer, steadier runs mean the tank was the culprit.
5. If the gauge reads wrong or sticks, replace it — a bad gauge sends you chasing the wrong fix.

When to call a pro

• The tank precharge and switch check out, but the pump still short cycles.
• Pressure drops right after the pump stops with no fixture open (possible down-well check valve or buried-line leak).
• The pump trips its breaker, runs hot, or delivers sand or air.
• You are replacing the pump or upsizing the tank and need the system matched.

Related across the site

• Sump pump check valves — the same backflow problem, in the basement
• Iron in well water — iron and scale can clog switch ports

Sources

• Amtrol Well-X-Trol installation instructions — precharge about 2 psi below pump cut-in.
• Square D pumptrol pressure switch instructions — cut-in/cut-out settings and safety.
• Grundfos SQ / SQE product literature — constant pressure operation.

More in this section

• Residential well pump basics
• Pressure tank precharge
• Replacing a 40/60 pressure switch
• Well pumps section hub