Troubleshooting

Well Pump Short Cycling: Why It Turns On and Off So Often

Frequent starts wear out a pump faster than almost anything else. The good news: short cycling is usually caused by the cheapest parts of the system.

By Well Pump Handbook EditorialPublished How we research

On this page
  1. Is it really short cycling? Time it
  2. The bucket drawdown test
  3. Short-cycling decision tree
  4. Causes and what to do about each
  5. What to do until it's fixed
  6. Sources
Short answer

Short cycling means the pump runs for only seconds before shutting off, then starts again soon after. In most homes the cause is a pressure tank that has lost its air cushion — a failed bladder or low precharge — so there's almost no stored water between cut-out and cut-in. The other common causes are a leak or a check valve that lets pressure bleed away (cycling even when no water is used), a tank too small for the pump, and a pressure switch or clogged sensing port that makes the switch chatter.

Why it matters

Minimum run time
Franklin Electric says a submersible motor should run at least 1 minute per start to get rid of the heat from starting.[1]
Starts per day
Franklin's maximum for single-phase motors: 300 starts per 24 hours up to ¾ HP, 100 starts for 1–5½ HP.[1]
What wears out
Franklin lists pressure switches, relays and capacitors, plus motor spline and bearing damage and overheating, as effects of rapid cycling.[1]

Is it really short cycling? Time it

You need a phone stopwatch and a view of the pressure gauge.

  1. Open one faucet or shower at a normal flow and leave it running.
  2. When the pump starts (you'll hear the switch click, or the gauge begins to rise), start the timer.
  3. Stop the timer when the pump shuts off at cut-out. That's the run time.
  4. Then time how long it stays off with the faucet still open. That's the off time.
  5. Close the faucet and watch for another 10 minutes: does the pump start again even though nothing is open?
Pressure over time for a normal pump cycle versus short cyclingA chart of system pressure over time between the cut-in and cut-out lines. The normal trace rises over about a minute and falls slowly while water is used. The short-cycling trace forms a tight sawtooth, rising and falling every few seconds. cut-outcut-in time → psi Normal: pump runs 1+ min, then rests Short cycling: runs seconds, restarts quickly

Illustration, not measured data. The shape is what matters: short cycling looks like a tight sawtooth on the gauge.

What your timing results suggest
ResultWhat it points to
Runs a minute or more, rests a whileNormal operation.
Runs under 20–30 seconds with a faucet open; gauge swings fast between cut-in and cut-outLittle or no drawdown: waterlogged tank, low precharge, failed bladder, or a tank too small for the pump.
Restarts with every faucet opening, even brieflyAlmost no stored water — typical of a waterlogged tank.
Starts again with nothing openPressure is leaking away: a fixture, a buried-line leak, or a check valve letting water run back down the well.
Switch clicks rapidly (chatters) right at cut-in or cut-outPressure switch or a clogged sensing nipple; sometimes a pump near the end of its range.

The bucket drawdown test

This measures how much water the tank actually delivers between pump cycles — the drawdown. It's the most useful number you can collect before calling anyone.

Safe to check

  1. Let the pump run until it shuts off at cut-out. Note the gauge reading.
  2. Turn the pump's breaker off.
  3. Open a faucet near the tank (a laundry tub or hose bib) into buckets you can measure.
  4. Close the faucet when the gauge reaches your cut-in pressure. Measure the gallons you collected.
  5. Turn the breaker back on.

Compare your result with what the tank should hold. A 30/50 system with the precharge set correctly delivers roughly 30% of the tank's total volume; a 40/60 system about 26% (The Driller's worked example: 25.1 gallons from an 85-gallon tank at 30/50 and 21.9 gallons at 40/60).[2] If you collect a small fraction of that, the tank has lost its air cushion. Our tank size calculator shows the expected drawdown for any tank and switch setting.

What happens inside a bladder pressure tank during one pump cycleThree tanks. Empty, the air side is at the precharge pressure of 28 psi. At the 30 psi cut-in only a little water remains. At the 50 psi cut-out, water has compressed the air and fills about a third of the tank. The water released between cut-out and cut-in is the drawdown. air Empty air at 28 psi air water Pump starts cut-in 30 psi air water Pump stops cut-out 50 psi draw-down

Illustrative levels for a 30/50 switch with a 28 psi precharge. The usable water between cut-out and cut-in is the drawdown; everything else in the tank is air or water that never leaves.

Short-cycling decision tree

  1. Does the pump start again when no water is being used?

  2. Close the valve on the house side of the tank tee and watch the gauge with the pump off. Does pressure still fall?

    • Yes Pressure is escaping between the tank and the well: a check valve leaking back, a buried-line leak, or a leak at the tank tee. See cause 3.
    • No Go to step 3.

  3. Pressure holds with the house valve closed. Can you find a running toilet, dripping fixture, softener or filter regenerating, or a wet spot?

    • Yes Fix that leak — the pump is responding normally to water loss.
    • No Hidden plumbing leak. A plumber can pressure-test the house lines.

  4. With the pump off and the tank drained to 0 psi, press the tank's air valve briefly. Does water come out?

  5. Check the air pressure with a tire gauge (tank still drained). Is it close to 2 psi below your cut-in?

  6. Did the bucket test deliver close to the expected drawdown, and does the pump still run under a minute?

Causes and what to do about each

1. Waterlogged tank (failed bladder or diaphragm)

Symptoms
Pump starts almost every time a faucet opens; pressure drops the moment water runs; the switch clicks constantly.
What sets it apart
Water comes out of the tank's air valve, or there's no air pressure at all with the tank drained. The tank may sound solid, not hollow, near the top when tapped.
Safe checks
Power off, drain the tank through a nearby faucet until the gauge reads zero, then check the air valve.[3]
Don't
Don't keep "burping" or recharging a tank that has water on the air side — it will flood again. Don't try to tip or move a waterlogged tank: water weighs about 8.3 pounds per gallon, so a large tank full of water can weigh several hundred pounds.
Likely fix
Replace the tank. HomeGuide reports $800–$1,500 installed on average, depending mainly on size.[4] See how to tell if a pressure tank is bad.

2. Low precharge (bladder intact, air leaked out)

Symptoms
Shorter run times than you remember; pressure falls faster than it used to.
What sets it apart
Air, not water, comes from the air valve — but the reading with the tank drained is well below cut-in minus 2 psi.
Safe checks
Read the precharge with the pump off and tank empty. The target for a pressure-switch system is 2 psi below cut-in — 28 psi for 30/50, 38 psi for 40/60 — per Amtrol and Pentair.[5][6] Use the precharge calculator for other settings.
Don't
Don't simply pump air into an older tank. Amtrol warns that a tank which has lost air or cycle time may have internal corrosion, and that re-pressurizing a corroded or damaged tank can make it burst.[5] Look for rust at seams and fittings, and follow your tank maker's instructions.
Likely fix
A contractor resets the precharge on a sound, newer tank, or replaces a tank that is corroded or keeps losing air.

3. Leak or check valve letting pressure bleed away

Symptoms
The pump comes on by itself every few minutes (or hours) with nothing running. Sometimes you can hear water running back toward the well, or a bang (water hammer) when the pump starts.
What sets it apart
Pressure drops with the house valve closed and the pump off.
Safe checks
The house-valve test above. Walk the buried line route for wet ground.
Don't
Don't have a check valve drilled or removed as a "fix." Franklin says only positive-sealing check valves should be used, and that missing, leaking or drilled check valves cause backspin, upthrust and water hammer that damage pumps and motors.[1]
Likely fix
Replace the check valve (the one in or near the pump means pulling the pump) or repair the line. Franklin calls for a check valve within 25 feet of the pump when the pump has none built in, and says swing-type check valves should never be used with submersibles.[1]

4. Tank too small for the pump

Symptoms
The tank passes every air check, the bucket test matches its rated drawdown, yet the pump still runs less than a minute. Often starts after a bigger pump was installed.
What sets it apart
Everything tests "good" — the numbers just don't fit.
Safe checks
Find the pump's flow in gallons per minute (from its label or model curve) and use the tank size calculator. Water Well Journal's method: pump GPM × minimum run time (1 minute below 2 HP, 2 minutes at 2 HP and up) gives the drawdown you need.[7]
Don't
Don't widen the switch differential beyond 20 psi without checking with the tank manufacturer. The Driller recommends confirming this first.[2]
Likely fix
A larger tank, or a second tank piped in. See pressure tank sizing.

5. Pressure switch or clogged sensing port

Symptoms
Rapid chattering at the switch, the pump starting and stopping within a second or two, pressure readings that jump.
What sets it apart
Tank checks are normal, but the switch behaves erratically.
Safe checks
Listen and watch from outside the switch. Note whether it happens at cut-in, cut-out, or both.
Don't
Don't remove the switch cover with power on. Pentair's instructions start with disconnecting power — the terminals are hazardous whenever the breaker is on.[6]
Likely fix
Replace the switch and the ¼-inch nipple or sensing tube. HomeGuide lists a pressure switch replacement at $150–$200 installed.[8] See pressure switch troubleshooting.

Short cycling is one of several symptoms with overlapping causes; the troubleshooting symptom map shows how it relates to the others.

What to do until it's fixed

  • Use water in longer, steadier draws (fill a tub rather than many short faucet uses) — each start is the wear, not the run.
  • If the pump restarts with no water in use, consider turning the breaker off between uses until the leak is found.
  • If the switch is chattering continuously, turn the breaker off and call for service.
Check my pressure tankDiagnose another symptom

Sources

  1. Franklin Electric. Submersible Motors: Application, Installation & Maintenance (AIM) Manual, 60 Hz. Accessed Sept. 28, 2026.
  2. The Driller. How to Calculate and Control Pressure Tank Drawdown — Bob Pelikan (Feb. 1, 2006). Accessed Sept. 28, 2026.
  3. Water Systems Council (wellcare). Pressure Tank Pre-charge — information sheet. Accessed Sept. 28, 2026.
  4. HomeGuide. How Much Does It Cost to Replace a Well Pressure Tank? (article dated July 25, 2025). Accessed Sept. 28, 2026.
  5. Amtrol. Well-X-Trol Residential Pre-Pressurized Well Tanks — Installation & Operation Instructions (WX-101 through WX-350). Accessed Sept. 28, 2026.
  6. Pentair. Adjusting Well Pump Pressure Switches (instruction sheet U80-129). Accessed Sept. 28, 2026.
  7. Water Well Journal. Tank Selection by the Numbers — David L. Kill, PE (April 19, 2022). Accessed Sept. 28, 2026.
  8. HomeGuide. How Much Does Well Pump Repair Cost? (article dated Aug. 6, 2025). Accessed Sept. 28, 2026.

We cite manufacturer documentation and public agencies first. Read how we choose and check sources.

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