A well pump that turns on and off every few seconds is short cycling. Most often, the pressure tank has lost its air. Other possible causes include an incorrect precharge, a worn pressure switch, a leak, or a check valve that no longer holds water. At Wilfrid David in Chénéville, this is one of the well problems we regularly address across La Petite-Nation, and it should be corrected promptly, since every start wears the pump.
Why the pump starts too often
A pressure tank holds a cushion of air above a diaphragm or bladder. The pump fills the tank with water, the air compresses, and the pressure switch stops the pump when the high setting is reached. When you open a tap, the air pushes water into the plumbing, and the pump only restarts once pressure falls to the low setting. This provides a good reserve of water between starts.
Without air, that cushion disappears. The tank fills in a few seconds, the pump stops, then restarts as soon as you draw a glass of water. The gauge shows it clearly: the needle rises and falls rapidly.
The manual from a major submersible motor manufacturer explains that frequent starts wear out the controls and can damage or overheat the motor. The same manual recommends that a motor run for at least one minute every time it starts. A pump restarting every fifteen seconds falls well short of that.
A waterlogged tank
This is the first cause to check. The same motor manufacturer's troubleshooting chart names it explicitly: waterlogged tank, check the air charge.
Two clues help identify it. When you tap gently on the tank, the top often sounds as full as the bottom rather than hollow. And if you press the air valve on top (similar to a tire valve) and water comes out instead of air, the diaphragm or bladder is torn. One tank manufacturer uses exactly this test: water at the valve means the water cell needs to be replaced. In that case, adding air will not solve the problem. Our article on the signs a pressure tank needs replacing covers this in more detail.
An incorrect precharge
Even a tank in good condition performs poorly if the air is not at the correct pressure. According to manufacturers, the precharge is set 2 psi below the pressure switch cut-in: 28 psi on a 30/50 setting and 38 psi on a 40/60 setting.
Manufacturers all describe the same procedure for checking it. Switch off the pump at the electrical panel. Open a tap near the tank until the pressure drops to zero. Only then place a tire gauge on the air valve. The reading should never be taken with water under pressure in the tank, as it would be inaccurate.
An important caution applies. A major tank manufacturer's manual states that you should not add air to a tank that has lost air, shows rust on the outside, or is cycling faster than before. Lost air can be caused by internal corrosion, and re-pressurizing the tank can cause it to burst. The same manual specifies that only qualified professionals should check or adjust the precharge. We therefore recommend limiting yourself to reading the precharge, if you are comfortable doing so, and leaving the re-inflation or replacement of a tank that has lost its air to us.
The pressure switch
The pressure switch is the device that controls when the pump starts and stops. Over time, its contacts can burn or stick, and its setting can drift. The motor manufacturer lists it among the possible causes, including welded contacts and incorrect adjustment. Because it contains live terminals, it should never be opened while the power is on, and its adjustment springs should not be altered without the proper knowledge.
A leak or a faulty check valve
Close every fixture: taps, toilets and washing machine. Then watch the gauge. If the needle still drops and the pump restarts on its own, water is escaping somewhere.
- A toilet that runs continuously, which is often easy to overlook.
- An outdoor tap, or a pipe seeping in the crawlspace.
- The line between the well and the house; a patch of ground that is always wet can be a clue.
- The check valve. If it stays open, water flows back down the well every time the pump stops. The troubleshooting chart confirms it: a damaged check valve will not hold pressure.
A leak in the buried line and a worn check valve produce the same symptom on the gauge. An accurate diagnosis calls for a professional.
When to call a professional
If the pump starts every few seconds, contact us without delay at 819-428-3161. The same applies if water comes out of the air valve or if the gauge drops while everything is closed. We check the tank, the precharge, the pressure switch and the check valve, and replace any worn components. If you have no water at all, start with what to check when there is no water. Evenings and weekends, emergencies are handled on call. For more information, see our wells and pumps page.
Filed under Wells and pumps