Causes of & cures for water pump short cycling on and off:
This article explains how to diagnose all of the various causes of well pump short cycling - what causes the well pump to run too often or to turn on and off too rapidly.
By understanding the cause of too-frequent water pump on/off cycling we also point to the necessary repair.
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Short cycling of a water pump which is defined at SHORT CYCLING WATER PUMP means that the water pump or "well pump" turns on and off too rapidly or too frequently when water is being run in the building.
If this is the problem with your water pump, this article (below) describes the most common causes of this problem.
The most-common cause of pump short-cycling is loss of air in the water pressure tank.
This is the topic discussed at length below, and corrective steps are detailed. However there could be other, less common plumbing problems that cause this symptom. Before "fixing" a problem it's useful to identify the correct problem, less we waste time, effort, and money.
This article describes the most likely water pump short cycle causes include the following, listed more or less in the order of probability:
Our complete diagnostic list of all known causes, diagnostic steps, and repair procedures for well pump short cycling is
at WATER PUMP SHORT CYCLING DIAGNOSIS TABLE
Loss of sufficient air charge in the water tank is perhaps the most common cause of water pump short cycling, and is a particularly common problem with older non-bladder type water pressure tanks or with newer bladder type water tanks if the bladder has become damaged.
The remedy for a water tank that has lost its air charge is pretty easy and is discussed in great detail below at
A defective water pressure control switch. Switch contacts can burn-up, or the opening into the switch
which senses the water pressure in the system can become clogged with sediment or debris. This usually
shows up as failure of the pump switch to turn on or off at all, rather than short cycling. But the switch could be damaged or improperly adjusted, causing "short water pump cycling."
Technical note: Clogging of the Water Pump Pressure Control Switch if your water has a high level of silt, debris, or minerals, it's possible that the tubing or piping connecting the pump pressure switch to the pump or water piping, or the pump switch bottom orifice through which the pressure switch senses the water pressure in the system has become clogged.
The small diameter of this tubing and still smaller diameter of the pump switch orifice makes clogging easy if your well water is high in sediment or minerals.
A clogged water pump pressure control switch will often fail to turn on the well pump at all, even though the pressure in the system has dropped below the water pump "cut in" pressure. Reader Jeff Crosby reported an example of this pressure switch clog problem:
[When our well pump kept short cycling and I was unable to get the well pump pressure control switch to work properly, ...] I ended up calling the pump service company to come over. There was an extreme amount of mineral buildup inside the pump where the copper tubing initially comes out to travel to the pressure switch. I thought about checking that out but did not know how funny.
There has always been an awl sitting on the pump base for the longest time. One of their maintenance guys left it there long ago. Now I know why - ever since that date when they come do their yearly check up they knock out this sediment [using the awl to open the tubing so that the pressure switch can accurately sense the water pressure in the system]. -- Jeff Crosby
On rare occasions we can tap on the well pump control switch and it will begin working again, but not for long, and not reliably. Another water pressure control switch failure is the rupture of a rubber disk or "bladder" inside the switch itself. If you detect or suspect a defective pressure control switch, try replacing it with a new one.
We see a similar problem affecting water pressure gauges on private water systems: debris or mineral deposits can clog the pressure sensing orifice on the water pressure gauge, causing it to fail to respond at all, or to respond inaccurately to changes in water pressure.
When we find a clogged water pump pressure switch or the tubing connected to it, or a clogged water pressure gauge, we replace those items. A well pump pressure gauge that does not respond to pressure changes is potentially unsafe as it could lead to excessive pressurization of the water tank and building piping.
A blockage in the water supply piping. For example, a clogged or nearly-clogged water filter can cause the pump control to cycle on and off rapidly. This is because the blockage causes water pressure (between the pump and the filter) to rise very rapidly when the pump turns on. The author once replaced a pump control switch only to discover that the real problem was a clogged filter, so check this item if you have filter(s) installed on the system.
A clogged water filter can block water flow between a pump and water tank or between a water tank and the rest of the building.
Try changing the water filter by installing a new cartridge; temporary diagnosis can be
made by simply removing a suspect water filter cartridge from its canister entirely. I've also seen a clogged
water filter cause water pump short cycling, with a rapid "on-off" pump cycle (which is bad for the pump and
pump relay switch.)
Tips for diagnosing water filters as a cause of well pump short cycling:
If your water filter has a bypass valve, try opening that valve to see if the short cycling stops. If there is no bypass valve for your water filter, turn off the pump and valves around the water filter, then remove the water filter cartridge and reassemble the unit. If the short cycling problem stops you probably had a clogged water filter. Replace the water filter cartridge.
Too much air in the water pressure tank - overcharging: If a well pump pressure control switch is set to cut on at 30 psi and off
at 50 psi, at the cutoff point the water tank is empty (a bladder type captive air tank) or nearly empty (a traditional water tank)
of water, and the air pressure in the tank is about at 30 psi.
The well pump comes on and re pressurizes the tank with incoming water, until the tank pressure of both air and water increases to the pump cut-off point of 50 psi. If someone puts too much air in a conventional water tank (overcharging) the excess air usually simply blows out of a nearby faucet the next time the water is run, and the system will correct itself. But if someone overcharges a captive air water tank the excess air can't escape.
A defective or ruptured captive-air water tank bladder: it sounded so weird we didn't believe it at first, but one reader explained that the water-containing bladder in their WellXTrol™ type water tank had collapsed and become stuck on itself.
The effect of a water tank air bladder that has collapsed and adhered to itself was that the water pressure tank would accept only a very small volume of water before the stuck-up bladder would reach the pump shut-off pressure. The bladder was replaced and things got back to normal.
If your water pressure tank has a ruptured or torn or leaky bladder that can cause short cycling of the water pump. You might "get by" temporarily by forcing air into the water tank - sometimes this works until you can get a new bladder installed or until you install a new water tank entirely.
But sometimes adding air to the water tank with a torn or ruptured bladder won't work - that suggests that the bladder has become adhered to itself inside the water tank.
Your site was very helpful for information on "short cycling" of a water well pressure sensor switch and pump relay. However, none of the listed causes matched my issue, so I wanted to relate what I discovered.
After a very cold night (approx -25F), we had some freeze-up and ruptured pipes in the system. I thawed everything and replaced the broken pieces, but the well pump was short cycling, clicking on and off.
I knew there had to be an obstruction in the supply line leading to the pressure switch, but I had thawed the line thoroughly. In a moment of insight, I realized that there might be ice in the pressure tank itself, so I shined a halogen work light on it for a few hours, and that solved the problem. Thanks again for the information your site provides. It really helped. - E.T. 12/18/2013
While it is common for water supply pipes to freeze at one or more cold spots in a home during very cold weather, it is more unusual for a water pressure tank itself to freeze up - though I could imagine that if pipes are frozen around the pressure tank, the pressure tank outlet tee itself might also freeze solid - causing well pump short cycling.
If your freeze-up occurred because the whole building lost heat for a time during very cold weather I can understand a more broad range of frozen plumbing pipes, valves, tees, and even a pressure tank or toilet tank (which sometimes will also burst when frozen).
If the freeze-up of the pressure tank that you cite occurred when your home had not acutally lost heat, I'd look at some freeze-protection steps to prevent a recurrence. The first choice is finding and sealing drafts, next adding insulation, and third, in some difficult spots adding a heat source. We have seen successful freeze protection in well pits with just the addition of the small amount of heat provided by a 75W incandescent light bulb hung close to the piping and pressure tank.
See Older steel Tanks for photos and text describing how this happens and how you might spot an intermittent air leak from a faulty water storage tank.
The Well-X-Trol should be installed as close as possible to the pressure switch. This will reduce the adverse effects of added friction loss and pressure switch bouncing, and the difference in elevation between WELL-X-TROL and switch.
Really most pressure tanks will work if placed almost anywhere. But if you have a problem such as pressure switch bouncing (the switch turning the pump on and off rapidly at the start or end of a pumping cycle) you can relocate the pressure switch to the new larger tank and run a longer wire to the pump or pump control relay. Other causes of pressure switch bounce and well pump short cycling are discussed in this same document.
Be sure to see our separate diagnostic guide Table to well pump short cycling in table form at WATER PUMP SHORT CYCLING DIAGNOSIS TABLE.
If there is a hole in the well piping anywhere between the bottom of the well and the water tank itself, water squirting out of this hole during every pump-on cycle tends to enlarge the hole over time. When the water loss at this leak is great enough, the well pump has to run longer to reach the pump control cut-off pressure, and at the same time, water running back out through this same hole drains pressure and water from the system, causing the pump to have to run more often.
If the leak in the well pipe is below the water level inside the well you will still have water and water pressure loss back through the leak when the pump stops, but you probably won't find air entering the well piping.
Watch out: If the well piping leak is severe enough the well pump may run continuously - a problem you'll notice quickly if the well pump is inside the building. But if the pump is an in-well submersible unit, it may be running continuously without anyone noticing it - until the pump fails.
Using a plumbing fixture during a power outage? Reader M.L. offered these comments [ edited for clarity and brevity]
I've searched your site for reasons why pressure is lost in a system if, during a power failure, a fixture is used somewhere in the house; in my case, a toilet. I came across it being mentioned on one of your pages, but no solutions or options offered.
After searching other sites, I drained and flushed my pressure tank; only to now have short cycling issues start with the pump.
I found your page dealing with "causes for short cycling & solutions" . It did not, however, mention the symptoms I was experiencing.
Thank you for the notes, M.L. we include them here with some clarifying comments and technical corrections. Working together makes us smarter.
The most common cause of lost water pressure after a power failure is loss of pump prime which in turn was caused by a leaky check valve or foot valve. However loss of prime will leave the pump running constantly with no water delivered - shut off the pump to avoid ruining it. This problem does not cause short cycling. Please see
PUMP PRIME, REPEATED LOSS of for a description of that problem
and please see
PRIME the PUMP, HOW TO to get things going again.
Then to fix the underlying problem see
FOOT VALVES - Editor
I located a video dealing with changing a pressure switch. In it, mention was made as how to properly drain and fill the expansion tank. and what happens if you don't do it right.
As your site comes up quite a bit when a Google search is made dealing with this, please allow me to submit the following for you to add to your "causes for short cycling" page.
When the pressure tank is drained, either for work (replacing gauge or switch) and likely even for the recommended regular (annual) maintenance to drain dirt build-up (which apparently reduces the possibility of the base of the tank prematurely rusting out) It is necessary to also drain the air pressure in the tank. This will allow all of the water to drain. If this is not done, water will still remain in the tank.
The reader comment above is not quite correct. In fact the air pressure in the tank is what pushes water out of the pressure tank during the draining process. However you might need to check that the proper air charge is in the tank when it is returned to service. And if a tank has become waterlogged there is no air to push water out of the tank. IN that case you'll need to open an air inlet (perhaps at the tank air charge valve) to drain water from the pressure tank. - Editor.
See WATER TANK DRAIN VALVE - Editor
When the tank is filled with water again, it will appear to fill regularly up to about 30 lbs. at which point the needle on the pressure gauge rapidly shoots up to 50 - 55 lbs. and the pump shuts off. When water is first run, there seems to be proper water pressure at the taps, but this drops off very fast, and the pump begins to short cycle.
This is because of the water still in the tank and the apparent air-lock this has created. When the tank was refilled (without having had all the pressurized air drained) the pressure tank did not properly fill and only the house lines were pressurized. When the tap was open this causes the pressure to rapidly drop, causing the short cycling.
Not quite correct: this is not an air lock problem but rather a sign of a water-logged pressure tank. That can occur because someone thought they had properly drained the tank and inserted the proper air charge when in fact they have not done so. To get the proper air charge in the tank we need either to drain it completely by gravity or we need to pump air into the tank.
See WATER TANK AIR, HOW TO ADD - Editor
To avoid this: Turn off supply valve to house, after pressure tank. Drain tank. Drain air pressure from tank. Re-pressurize tank.
Clarifying: you won't need to "drain air pressure from the water tank": if you drain the tank completely you'll also allow any air pressure above ambient to blow out of the tank drain.
There may be some confusion between a bladderless water pressure tank and tanks that include an internal bladder keeping water and air separate. In case someone has over-charged the air pre-charge in an internal bladder type tank you'll need to release the excess air through the tank's air valve. Set the air pre-charge pressure to 2 psi below the pump control switch CUT-IN pressure and you'll be OK. - Editor
Turn well pump back on and allow to re-fill with water (gauge should now fill slowly and steadily to set cut off point).
Open supply line tap to house.
To confirm proper operation and no more short cycling, open tap in sink and monitor gauge. All should operate properly now.
Based on the number of similar questions regarding this situation I came across while searching for answers, I'm sure this will come in handy.
- M.L. 6 Dec 2014
Short cycling of a water pump (which is discussed in this article) means that the water pump turns on and off too rapidly or too frequently when water is being run in the building. We also provide a complete
SHORT CYCLING DIAGNOSIS TABLE that lists all possible causes of well pump rapid cycling on and off.
If you are not sure what "water pump short cycling" means or how it is recognized, see
SHORT CYCLING WATER PUMP.
Intermittent water pump cycling which is discussed at
INTERMITTENT WATER PUMP CYCLING When No Water is Running means that the water pump comes on for no apparent reason.
Loss of water pressure means that the pressure with which water enters a plumbing fixture has become too slow, or is sometimes too slow or weak in water flow rate, or water flow may stop entirely.
See WATER PRESSURE LOSS DIAGNOSIS & REPAIR
Continue reading at WATER PUMP SHORT CYCLING DIAGNOSIS TABLE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Or see WATER PUMP SHORT CYCLING CAUSE FAQs - diagnostic questions help understand the causes of well pump switch cycling on and off quickly
Or see WATER PUMP SHORT CYCLING FAQs for diagnostic questions that explain why the pump cycles on and off quickly
Or see WATER TANK AIR, HOW TO ADD
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