Waterlogged Pressure Tank? How to Stop Well Pump Short Cycling

Your pump clicks on, runs a few seconds, clicks off, and then does it again the moment someone washes their hands. That rapid on-off is called short cycling, and the most common cause is a waterlogged pressure tank. Left alone, it wears out the pressure switch, overheats the motor and can kill a pump years early. Here is how to confirm it and fix it.

What a pressure tank does

A bladder or diaphragm tank holds a cushion of compressed air above a reservoir of water. When you open a faucet, the air pushes water out so the pump doesn't have to start for every glass of water. The usable water between pump start and stop is called drawdown. When the air cushion is lost, drawdown drops to almost nothing and the pump starts and stops constantly.

Signs of a waterlogged tank

  • The pump turns on and off every few seconds when water is running.
  • The pressure gauge jumps quickly between cut-in and cut-out.
  • The whole tank sounds or feels solid and heavy when you tap the top (it should sound hollow above the water line).
  • Water spits out of the air valve when you press the pin. This means the bladder or diaphragm has failed.

Check the air pre-charge (10 minutes)

  1. Turn off power to the pump.
  2. Open a faucet near the tank and let it run until no more water comes out and the gauge reads zero.
  3. Check the air valve on top of the tank with a tire gauge.
  4. Set the pre-charge to about 2 PSI below your pressure switch cut-in: 28 PSI for a 30/50 switch, 38 PSI for 40/60. Add air with a small compressor or let some out.
  5. Close the faucet, restore power and watch a full cycle.

If the air reading was low, re-charging may fix it. If the tank loses air again within weeks, or water came out of the valve, the diaphragm has failed and the tank needs replacing.

Other causes of short cycling

  • Tank is too small for the pump's flow. See our pressure tank sizing guide.
  • Leaking check valve or foot valve lets pressure drain back down the well, so the pump restarts with no water in use.
  • Leak in the house: a running toilet or dripping outdoor spigot.
  • Clogged pressure switch tube gives a false reading. Clean it or replace the pressure switch.

Why winter makes it worse

Tanks in cold garages and pump houses lose a little air pressure as the temperature drops, and short cycling motors heat up in tight, insulated enclosures. A quick pre-charge check in the fall is cheap insurance.

Replace or add a tank?

A failed diaphragm can't be repaired. Replace the tank with one of the same or larger drawdown. Flexcon Challenger tanks are a popular choice with well-system installers; see the PC66FR (20 gal), PC122 (33.5 gal) and PC244FR (81 gal), or all pressure tanks. If you can't fit a bigger tank, a CSV1A Cycle Stop Valve keeps the pump running steadily during long draws and is a proven fix for short cycling with a smaller tank.

Step-by-step: replacing a failed tank

  1. Turn off power and drain the system to zero pressure.
  2. Note the pressure switch setting and measure the space available.
  3. Disconnect the tank from the tank tee and remove it.
  4. Check the new tank's factory pre-charge and adjust it to 2 PSI below cut-in before you connect it.
  5. Install the new tank on the tee with fresh thread sealant, restore power and check every joint for leaks.
  6. Time a full pump cycle. It should run at least a minute.

When to call a pro

If the pump keeps cycling with a new, correctly charged tank and no leaks in the house, the problem is likely down the well (a check valve or drop pipe) and a well contractor should pull the pump. Call us first with your pump and tank models and we'll help you narrow it down.

Quick checklist

  • Pump off, tank empty, air checked.
  • Pre-charge set 2 PSI under cut-in.
  • No water from the air valve.
  • No running toilets or dripping spigots.
  • Pressure switch tube clear.
  • Run time at least 1 minute per start.

FAQ

How often should a well pump cycle?

As a rule of thumb, a pump should run at least one to two minutes each time it starts. Starts every few seconds mean short cycling.

Can I drain a waterlogged bladder tank and fix it?

Old-style plain steel tanks without a bladder can be drained and re-aired. Bladder and diaphragm tanks get waterlogged only when the air charge is low or the bladder has failed. Re-charge first; if it fails again, replace it.

How long do pressure tanks last?

It varies with water quality and how hard the system cycles. Many last 10 years or more. Short cycling and wrong pre-charge shorten that.

Will short cycling damage my pump?

Yes. Each start draws a surge of current and heats the motor. Frequent starts wear switch contacts and shorten motor life.

Need a hand? Call our pump team at (866) 202-8388 (Mon–Fri, 9 AM–5 PM ET) or email help@supremewatersales.com with your pump model, well depth and tank size. We will tell you what fits before you buy, no obligation.

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