Why Does My Well Pump Short Cycle?
If your well pump turns on and off every few seconds — clicking rapidly whenever you run water — that's short cycling. It's one of the most damaging things that can happen to a well pump, and it's almost always caused by one specific problem.
Short cycling puts enormous stress on the pump motor. A pump rated for 300 starts per day can accumulate that in a few hours of short cycling. Address this immediately — it will destroy your pump.
What Is Short Cycling?
A healthy well pump cycles on when pressure drops to ~40 PSI and off when it reaches ~60 PSI. That cycle should take 1–2 minutes under normal household use. Short cycling is when the pump turns on and off every few seconds — sometimes 10–20 times per minute.
Each pump start draws a surge of electricity (3–5x the running current) and puts mechanical stress on the motor bearings and impellers. A pump that short cycles for even a few hours accumulates the equivalent of weeks of normal wear.
The #1 Cause: Failed Pressure Tank Bladder
In over 90% of short cycling cases, the cause is a failed pressure tank bladder. Here's why:
The pressure tank contains a rubber bladder that separates a pre-charged air cushion from the water supply. The air cushion absorbs pressure fluctuations so the pump doesn't have to start every time you use a small amount of water.
When the bladder ruptures or loses its air charge, the tank fills completely with water. There's no longer any air cushion to buffer pressure changes.
Now every tiny pressure drop — opening a faucet, flushing a toilet — causes the pressure switch to kick the pump on. The pump builds pressure in seconds, the switch shuts it off, and the cycle repeats immediately.
Other Causes of Short Cycling
Incorrect Pressure Tank Pre-Charge
Even if the bladder is intact, the air pre-charge can leak out over time. The tank should be pre-charged to 2 PSI below the pump cut-in pressure (typically 38 PSI for a 40/60 system). Check the Schrader valve at the top of the tank with a tire gauge.
Pressure Switch Set Too Close Together
If the cut-in and cut-out pressures are set too close (e.g., 50/60 instead of 40/60), the pump will cycle rapidly because the pressure band is too narrow. This is less common but worth checking.
Oversized Pump
A pump that's too powerful for the well or the pressure tank will build pressure so quickly that the tank can't absorb it, causing rapid cycling. This is common when a pump is replaced with a higher-capacity model without upgrading the pressure tank.
Leak in the System
A significant leak can cause pressure to drop so quickly that the pump cycles rapidly trying to keep up. Check for running toilets, dripping faucets, and wet spots near the pressure tank.
How to Diagnose Short Cycling
- Listen for rapid clicking near the pressure tank — that's the pressure switch cycling
- Tap the pressure tank from bottom to top with your knuckle — a waterlogged tank sounds solid throughout; a healthy tank sounds hollow in the upper half
- Check the Schrader valve at the top of the tank with a tire gauge — if water comes out instead of air, the bladder has failed
- Check the pressure gauge while running water — if pressure swings wildly (40 to 60 PSI in under 5 seconds), the tank has lost its air cushion
- Count pump starts — if the pump starts more than 6 times in 10 minutes of normal use, it's short cycling
Frequently Asked Questions
What causes well pump short cycling?
Short cycling is almost always caused by a failed pressure tank bladder. When the bladder ruptures, the tank fills completely with water and loses its air cushion, causing the pump to turn on and off rapidly with every small water use.
How do I know if my pressure tank bladder has failed?
Tap the pressure tank with your knuckle from bottom to top. A healthy tank sounds hollow in the upper half. A waterlogged tank sounds solid throughout. You can also check the Schrader valve at the top — if water comes out instead of air, the bladder has failed.
How much does it cost to fix well pump short cycling?
If the cause is a failed pressure tank, replacement typically costs $300–$600 including labor in Southern Maryland. If the short cycling has already damaged the pump motor, you may be looking at $1,500–$3,500 for a full pump replacement.
Real Job: Waterlogged Pressure Tank — Owings, MD
An Owings homeowner's pump was starting every 8–12 seconds. We found a completely waterlogged pressure tank — the bladder had failed and the pump was short-cycling hundreds of times per day. Same-day tank replacement saved the pump motor from destruction.
Read the full project storyReal Job: Low-Yield Well Pump Replacement — Dunkirk, MD
A Dunkirk homeowner had gone through two pump replacements in three years — both failed from short-cycling on a 0.4 GPM well. We installed a Cycle Stop Valve system that has run reliably for over a year.
Read the full project story