If you live on a private well and you can hear the pump click on, run for a few seconds, click off, and do it again a minute later, something is wrong, and it is almost always the same thing. It is called short cycling, it is easy to diagnose, and it is worth fixing quickly, because it quietly destroys the most expensive part of the system.
Short cycling means the well pump switches on and off far more often than it should, often every few seconds. The most common cause is a pressure tank that has lost its air charge or has failed, so the tank cannot hold a cushion of pressurized water and the pump must start every time a tap opens. Other causes are a worn pressure switch, a leak in the house or in the line from the well, and a clogged tank connection. Left alone it wears out the pump motor and the switch quickly.
- A pressure tank is the cushion of the system. When it fails, the pump does all the work and starts far too often.
- Short cycling is a symptom, not a fault in itself. The tank is the usual cause, but not the only one.
- Check the pressure gauge and listen to the cycle. Fast on and off with pressure swinging quickly points to the tank.
- Do not open electrical parts yourself. Turn the power off at the breaker before touching anything near the pump or the switch.
- A pump replaced without checking the tank is the classic way to pay for a second pump.
How a well system works, in one paragraph
A pump brings water from the well and pushes it into a pressure tank. The tank has a rubber bladder or diaphragm with air on one side and water on the other. As water enters, the air is compressed and the pressure rises. When it reaches the upper setting, a pressure switch cuts the pump off. When you open a tap, the compressed air pushes the stored water out, the pressure falls, and when it reaches the lower setting the switch starts the pump again. The tank is what lets you draw a good amount of water, such as a shower or a load of laundry, before the pump needs to start.
What short cycling is
If the tank cannot hold a cushion of water, there is no stored volume to draw from. Open a tap and the pressure falls straight to the lower setting, and the pump starts. Close it, and the pressure climbs back to the upper setting almost immediately, and the pump stops. The result is a pump that starts and stops over and over, often every few seconds.
Each start is hard on the motor. Starting current is several times the running current, and every start heats the motor windings and wears the contacts in the switch. A pump that should start a few times an hour can be starting thousands of times a day. The motor overheats, the switch burns out, and eventually the pump fails, usually at the least convenient moment.
The usual causes, in order of how often we see them
1. The pressure tank has lost its air charge
The air side of the tank is charged at the factory and slowly loses pressure, or a valve leaks. With little air, the tank becomes "waterlogged": it is mostly full of water and has no room to compress. Symptoms are fast cycling, pressure that swings quickly, and a tank that feels heavy and cold all over when you tap it. Often the air can be restored by recharging the tank.
2. The tank bladder has failed
If the rubber bladder or diaphragm has torn, water gets to the air side, and the tank cannot hold a charge however many times you add air. The giveaway is water coming out of the air valve when you press it. A failed bladder means the tank is replaced.
3. A worn or misadjusted pressure switch
The switch controls when the pump starts and stops. Burned contacts, a clogged port or a wrong setting can all cause erratic cycling. The switch is inexpensive compared with the pump, which makes it a good place to look, and also a reason not to ignore it.
4. A leak somewhere in the system
A dripping toilet, a leaking fitting, an outdoor tap left slightly open or a leak in the buried line from the well all let pressure drain. The pump starts to make it up, over and over. If the pump cycles when no one is using water, look for a leak.
5. A clogged connection or a problem at the well
A partly blocked line between the pump and the tank, a failing check valve or a pump that is wearing out can all change how the system behaves. These are less common, and are the reason a proper diagnosis looks at the whole system, not just the tank.
What you can check safely
Before anything else, know that this system is under pressure and connected to power. Turn off the breaker for the pump before you touch anything other than the outside of the tank.
- Listen and time it. With all taps closed, does the pump cycle on its own? If it does, there is a leak. If not, open one tap and listen: how long does the pump run, and how long is the pause? Cycles of a few seconds point to the tank.
- Read the gauge. The pressure gauge is on or near the tank. Watch it as you open a tap. A fast, steep drop to the lower setting means the tank is not cushioning.
- Tap the tank. A healthy tank sounds hollow at the top (air) and solid at the bottom (water). A tank that sounds solid all over is waterlogged.
- Look for leaks. Check the tank, the fittings and the base for water. A rusted or wet base is a warning sign.
- Check the date. Most pressure tanks have a manufacture date on the label. An old tank is a likely suspect.
What you should not do: open the pressure switch, adjust it without knowing the settings or work on the pump. The tank air charge is also something that has to be checked with the pump off and the tank empty of water, at a pressure set relative to the switch, and it is better done by someone who does it regularly.
Repair or replace
The honest answer depends on what is wrong. A tank that has lost its charge but is otherwise sound can be recharged. A tank with a torn bladder, or one that is rusted or leaking, should be replaced. A bad switch is replaced on its own. And whichever part failed, a good diagnosis looks at the others, because a pump that has been short cycling for a while may already be damaged.
At Royal Flush Affordable Plumbing we work on the plumbing side of a well system: the pressure tank, the switch and gauge, the connections and valves, and the line to the house. Tell us the pump type and depth if you know them, and what you see and hear, and we will say what we can do before we book. Our page on well pump and pressure tank service has more.
Protect the system afterwards
- Fix leaks quickly. A dripping toilet on a well system means thousands of unnecessary pump starts.
- Install a sediment filter at the main if the water carries grit, to protect fixtures and appliances. See our page on whole-house water filters.
- Check the tank charge once a year, or have it checked, and record the date.
- Know where the breaker is and how to switch the pump off in an emergency.
- Keep the area around the tank dry and clear, so a leak is noticed.
Frequently asked questions
How often should a well pump turn on?
It depends on how much water you use, but with a healthy tank the pump should run for a good stretch and then rest for a decent period while the tank supplies the house. Starting every few seconds is not normal.
Can I add air to my pressure tank myself?
Some homeowners do, but it has to be done with the pump off and power disconnected, the tank drained below the lower setting, and the pressure set a couple of pounds below the switch cut-in. If you do not know your switch settings, have it done by someone who does.
How long does a pressure tank last?
It depends on the water, the tank and how well the system has been looked after. A tank that has been waterlogged or short cycling for a while may be worn out. Age, rust or water at the air valve tell you it is time to replace it.
Will a bigger pressure tank stop short cycling?
A bigger tank holds more water and lets the pump rest longer between starts, which is good. But if the cause is a failed bladder or a leak, a bigger tank will not fix it. Fix the cause first, then size the tank to the household.
Why does my well pump run when nobody is using water?
Because the pressure is falling somewhere. The usual causes are a leak in a fixture or in a pipe, or a failing check valve. Look for a dripping tap or toilet, and check for wet ground over the line from the well.
Is a well pump covered by the same plumber as the rest of the house?
We work on the plumbing side of the system, and for the electrical and deep well parts we tell you honestly what we can do before we book. Describe what you have when you call.
Licensed Houston plumbers since 2007. Residential, commercial and industrial plumbing, 24 hours a day, with upfront pricing and no hidden charges.
