Short cycling water pumps:
Well pump turns on and off rapidly or too often: this article defines short cycling or rapid cycling well pumps and the various causes and cures for that problem.
We explain why rapid on-off switching of the water pump can be harmful and how it also affects building water pressure.
We explain that often sort cycling indicates the need for air in a water pressure tank. In companion articles we explain several ways to add air to a building water pressure tank, and how to detect and correct air and water leaks in a building water supply system where a private well is the water source.
We also discuss how to adjust the building water pressure by setting the cut-in and cut-out pressure on the pump pressure control switch.
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?
Several alternative procedures for adding air to a water pressure tank are described below along with advice about what to do when things go wrong, such as finding air and water leaks.
The illustration at page top is courtesy of Carson Dunlop Associates, Inc. in Toronto.
[Click to enlarge any image]
Short cycling of a 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. "Short cycling" means switching on and off every 30 seconds or less.
Extreme water pump short cycling may occur every second or less and means you should turn off the pump system to avoid damaging the pump or controls.
Reader question typical of pump short cycling problems:
9/1/14 William said: my well pressure switch keeps clicking on and off rapidly
If this is the problem with your water pump,
WATER PUMP SHORT CYCLING CAUSES describes the most common causes of this problem.
We also provide a complete
WATER PUMP 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,
read SHORT CYCLING WATER PUMP.
Intermittent water pump cycling which is discussed
at INTERMITTENT WATER PUMP CYCLING 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
2017/03/26 Anonymous said:
I have a small pressure tank and expect that the pump will have to turn on and off, but when is it cycling too fast? How many seconds should it run before kicking off and then restarting?
This question and reply were posted originally at WATER TANK DIAGNOSIS & REPAIR
How fast is "rapid cycling" or pump short cycling? good question.
IT depends on tank size, and more, on the water outflow or usage rate, and also the pump's pumping rate capacity in gpm for the whole system including total vertical lift, piping restrictions & distances.
If a pump, tank, piping, well are in perfect condition and the pump is cycling on and off for a moderate water flow usage rate such as someone running a bathroom sink faucet, then if the pump is turning on and off more often than every 30 seconds I'd want a larger pressure tank.
The pump manufacturers, are, however the final authority on this so you'll want to check with the company who makes your tank.
Certainly if a pump under any circumstances is turning on and off every few seconds or less, something's seriously wrong and the pump or its controls are likely to be damaged or to have a short life.
Watch out: For pressure boosting pumps that do not use any pressure tank (the control that turns the pump on and off is built into the pump), the pump turns on as soon as a plumbing fixture is opened to run water and runs all the time water is being run.
If the pressure booster pump that does not use a pressure tank (such as the new Grundfos Scala2 tankless pressure pump) is cycling on and off repeatedly in short intervals further investigation is needed: there may be a plumbing leak soaking your building.
Watch out: with tankless booster pumps: any small leak such as a running toilet or pinhole leak in a pipe may cause the pressure booster pump to cycle on and off more frequently than the manufacturer intends - risking damage to the pump.
The "water storage tank" is doing more than storing water. Its air charge acts like a spring to smooth the delivery of water in the building. If the building water supply pump is "short cycling" - coming on and off rapidly, you may need to add air to the water pressure tank.
This step is important to protect your private pump and well from damage due to short-cycling due to loss of air in the pressure tank. Short cycling of the pump motor can burn up the pump relay control.
The minimum that a building owner or occupant needs to know is that short cycling is an on-off cycle of the water pump in a house with a private water pump and water supply well system. The "short cycling" water pump is turning on and off rapidly, perhaps every 10 to 20 seconds or even more frequently.
Water pump short cycling can damage the pump or controls. Repair is needed at one or more of: the water pressure tank, water pump pressure control switch, water pump, water filter, or the well or building water supply piping. If you are not interested in tackling this easy repair yourself, call a plumber.
The sketch shown at the top of This article shows the components of a typical residential water well, water pump, water pressure tank, and water pump control system. Below we include other drawings and photographs of wells, water tanks, and their associated valves and controls.
At some properties the well pump may be inside rather than in the well as in this drawing, and on your tank the water pressure gauge may be mounted on a special air volume control fitting on the back of the water tank itself rather than as shown in this sketch. Sometimes people think this water tank is to "store" water for use in the building. That's rarely the case. Usually water is "stored" by being present in the well and in the ground around the well.
If a pump-operated water supply system is turning on and off rapidly (every few seconds) it would be smart to turn off the water or turn off electric power to the water pump and call a plumber promptly.
If your water pump comes on at odd times but is not short-cycling,
see INTERMITTENT CYCLING WATER PUMPS.
My airbladder tank pressure came pre set at 38psi but the pressure switch is 20/40 is this causing the switch to cycle on off on off? second question, there does not seem to be water in the tank,why? i get water from the spigot with pressure and the guage jumps right from 20 to 40 and back again. why? - Patty 9/17/12
Patty,
The pressure in the pressure tank should always be 2 psi below the cut in pressure of the pump. First, check the gauge when the pump first kicks in before shutting down the pump. Then, turn off the pump. Shut the water supply off to the pump, drain the pressure tank by opening the faucet furthest from the pressure tank, then release all the air from the pressure tank.
Refill the tank with air to 18 psi if the pump is actually cutting in at 20 psi. When you turn the pump back on it will fill the pressure tank and will stop cycling unless you have a leak somewhere or dirty filters. - reply from WaterWorks 9/21/2012
Watch out: After adjusting nut#2 you may need to check the actual operating water pressures in your system and adjust nut#1 to be sure that you are not pushing the cut-out (upper pressure) so high that the water pump never turns off (dangerous).
Or in a contrary case if you completely loosen the smaller nut #2 (dfifferntial adjustment) so that the pump differential between cut-in pressure and cut-out pressure is very small the water pump may short cycle on and off rapidly when water is being run in the building.
Normally the "pump on" cycle is 30 seconds to 90 seconds or longer, depending on water tank size, and the "pump off" cycle is the same or longer.
Short cycling of the water pump means that the water pump keeps turning on and off rapidly whenever you're running water at one or more fixtures in the building. The pump on-off cycle may be perhaps every few seconds, or perhaps every 10-20 seconds. This is a problem, which we diagnose, discuss, and for which we offer repair procedures below.
The minimum that a building owner or occupant needs to know is that short cycling can damage the pump or controls, and that action is needed.
These short cycling problems happen with both in-building jet pumps and with in-well submersible pumps. It's trickier to notice a short cycling submersible pump since you won't hear the pump motor, but you will hear the pump relay clicking on and off, or you can see the water pressure gauge cycling up and down rapidly.
If you are not interested in tackling this easy repair yourself, call a plumber. If the system is turning on and off rapidly (every few seconds) it would be smart to turn off the water or pump and call a plumber promptly since if you let this problem continue you're likely to damage a pump control or pump motor (expensive).
You can tell if your water pump system is "short cycling if:
If you don't know how to find your pump pressure gauge, pressure controls, switches and controls,
see WATER PUMP & TANK CONTROLS & SWITCHES
We give more description of how to detect short cycling of the water pump
How to Diagnose the Cause of a Well Pump that Keeps Turning On and Off
Watch out: before "fixing" a short-cycling well pump, you'll want to try for an accurate diagnosis of its cause - the right fix is cheaper than a whole collection of wrong fixes.
See WATER PUMP SHORT CYCLING CAUSES for an explanation of the most common causes of well pump short cycling
See WATER PUMP SHORT CYCLING DIAGNOSIS TABLE for a table that lists the all of the possible causes of well pump short cycling
Our articles listed above, WATER PUMP SHORT CYCLING CAUSES
and WATER PUMP SHORT CYCLING DIAGNOSIS TABLE list the corrective steps for a short cycling well pump - depending on the cause.
If it turns out that you want to just try the easy, quick, above-ground "fix" of adding air to the water tank, we describe how to correct water pump short cycling, in great detail and giving several methods,
at WATER TANK AIR, HOW TO ADD for conventional water tanks that do not use an internal bladder.
Bladderless water pressure tanks,
because the air charge and water are in the same container, can lose their air charge over time (air is absorbed into the water) and may need air added.
At BLADDERLESS STEEL WATER PRESSURE TANKS we discuss waterlogged water tanks and well pump short cycling.
See WATER TANK AIR, HOW TO ADD for details on how to add air to a water pressure tank.
Bladder type or captive-air water pressure tanks
and their repairs are described at WATER TANK TYPES
and at WATER TANKS HOW THEY WORK.
At WHAT GOES WRONG WITH an INTERNAL BLADDER TYPE WATER TANK?we discuss the combination of well pump short cycling and a burst water tank bladder and how this condition is identified and repaired.
See this detailed article on bladder-type "captive air" water tank diagnosis and repair:
at WATER TANK BLADDERS & CAPTIVE AIR
We just had our pump replaced after 18 years. Total cost with tax was $2400. Project was done on emergency basis on a Friday night and we were really stuck. During his visit the plumber/owner suggested we consider a larger pressure tank than our 20 gallon unit, also recently replaced.
The system worked well for many years and I don't see the need to purchase another larger tank. Any thoughts? - Wayne Ouellette
If your water tank is a newer bladder type, even a smaller 20-gallon tank gives the equivalent of a larger old style (non-bladder) tank in the draw-down cycle - the amount of time that you can run the water before the pump has to come on.
As long as your pump is not WATER PUMP SHORT CYCLING (which may shorten pump life), the gain from a larger tank is probably not much. If your tank is an older type with no internal bladder, the reason to go to a newer tank would be reliability and reduced maintenance.
Watch out: before you go to the trouble and expense of replacing a water pressure tank, make sure that you have correctly diagnosed the problem that you are "curing" - you wouldn't want to replace a water tank only to find that you still have the water pressure or quantity problem because another, perhaps less costly, part was at fault.
...
Below you will find questions and answers previously posted on this page at its page bottom reader comment box.
On 2022-11-16 by Jorge - Drummond Shallow Well Pump is short cycling
Our Drummond Shallow Well Pump is short cycling. It’s fed through a reservoir non pressurized tank that feeds water through gravity. It used to run less often but in the last couple months runs more often say for a flush it would run 2-3 times, now it runs 5-7 times.
From what I can tell the pressure is dropping too quickly from 50 to 30 psi causing it to run more often. What could be causing this? We changed the filter and there was debris in there.
On 2022-11-16 by InspectApedia (Editor) - Drummond Shallow Well Pump is short cycling
@Jorge,
Most likely the cause is one of those listed above on this page, such as loss of an air charge in the water pressure tank. Please read through that article and let me know how that works for you.
On 2022-04-30 by scott
our well during the night when there is no draw turns on every 10-11 minutes and runs for 20 seconds consistently all night is it in the pressure tank ?
On 2022-04-30 by Inspectapedia Com Moderator - leaky valve causing intermittent cycling
@scott,
Most likely there's a leaky check valve
See the diagnostics at
WATER PUMP INTERMITTENT CYCLING
On 2022-04-18 by Mike
My water pump short cycles rapidly every second. Checked the tank, set to 28psi. Replaced the 30/50 pressure switch. This started right after the pump impeller was replaced. Any ideas what can be checked? Thanks.
On 2022-04-18 by Inspectapedia Com Moderator - check pressure gauge as well s other diagnostic steps
@Mike,
Our best ideas of what to check are listed on the page above, but you might also want to watch the pressure gauge:
If the gauge shows the pressure falling rapidly from 50 psi down to 30 then the switch is doing what it should and there's water running somewhere or a leak in piping, such as a stuck or failed check valve between pump inlet and well.That might happen, for example, if yours is a jet pump that incorporates a check valve right at the pump inlet - something that was disturbed or omitted during impeller replacement.
On 2022-03-26 by Anonymous
Submersible pump runs constantly at 40psi. Pressure switch is 40/60 settings. Air pressure in 2gallon tank is 40psi
On 2022-03-26 by Inspectapedia Com Moderator
@Anonymous,
See the diagnosis and repair at
PUMP WON'T STOP RUNNING
On 2021-12-02 by Anonymous
my presurized shalllow well thank kikcs on and off repedly
On 2021-12-02 by Inspectapedia Com Moderator
@Anonymous,
The article above is designed to help you diagnose and fix exactly that problem: a well pump that kicks on and off repeatedly.
Do take a look and keep me posted, or ask if anything you read isn't cleaer.
On 2021-10-28 by jeni - Just wanted to say thank you for this. You saved me money.
Just wanted to say thank you for this. My small setup(shallow well pump in the garage) was switching off and on every 5-10 seconds and puslating, went ahead and checked the air pressure in the bladder thanks to this article.... and it was at 0. Quick fix with just a bike pump and a tire gauge, back to 28 and all is well. Ya'll probably saved me 100$
(obviously I need to have a conversation with my children about touching the pump again)
On 2021-10-28 by inspectapedia.com.moderator
@jeni,
Thank you so much for the nice comment; we're really grateful when a reader finds our website useful and trusted.
Daniel
On 2021-10-23 by Larry Gilliam - Could this be a bad bladder in the tank?
My pressure is short cycling bringing the well pump on and off as the water is on. It does not cycle when water is off. Could this be a bad bladder in the tank?
On 2021-10-23 by inspectapedia.com.moderator - bad bladder can cause short cycling
@Larry Gilliam,
Yes, if the pressure tank bladder has a hole in it or is ripped, then water can leak into the air chamber and the tank can become waterlogged.
That in turn will cause short cycling of the water pump.
On 2021-10-20 by Anonymous - pressure switch is trying to go to 90 psi even a 100
What if your gage at pressure switch is trying to go to 90 psi even a 100 and u have little to no water pressure in
On 2021-10-20 by inspectapedia.com.moderator
@Anonymous,
Watch out: That could be a pump pressure switch control problem and it sounds dangerous as you could burst a water tank and injure someone nearby.Often the problem is simply that the gauge's water pressure inlet port is debris clogged. Try replacing the gauge.
First of all, my apologies if this question has already been asked and answered, I'm new to the site. I believe I have a short cycling problem. This is a cottage application.
The pump cuts in at 28 psi and charges to about 42 psi and then cuts out. When the pump cuts out the pressure on the gauge drops immediately to 30 psi.
Then of course after a short water usage the pump cuts in and repeats the above.
The cycle used to be charge up to 42 psi, cut out and settle at 40 psi, draw down to 30 psi and then the pump would cut in.
This problem started after I needed to replace a foot valve in the cistern. Do you think it's a pressure problem in my bladder tank? If so, how can I return it the original cycle described above. Thanks in advance for any assistance you can provide. - Dan Lowry 8/27/11
(Sept 1, 2014) william said:
my well pressure switch keeps clicking on and off rapidly
Reply:
Dan that sounds like short cycling to me. I've often seen that a pressure gauge reads higher when the pump is running and drops at pump shutoff. But when you add that running just a few gallons of water turns the pump back on, that suggests that the tank has lost its air charge.
If your tank really has an internal bladder, that's not supposed to happen. So if you have indeed lost the air charge, the bladder may be torn or damaged.
See the well pump short cycling diagnosis & repair articles we provide starting at
WATER PUMP SHORT CYCLING - home
William please see the short cycling well pump diagnostics at
WATER PUMP SHORT CYCLING CAUSES
and let me know how you make out
On 2016-06-01 by Nicole - water goes off and on every 5 seconds
I've only had this house a little over a year and recently my pump has been short cycling.
Any time my water is running the pump kicks on about every 5 seconds. Sometimes while taking a shower I will lose water completely but it will kick back on after 2-5 minutes.
My tank says it's a Controlled Air Water Tank. Somebody help me. From what I'm reading I think my bladder has burst so should I just get a new tank or just repressurize it
On 2016-06-01 by (mod) - well pump is short cycling on and off too often
Nicole
Above you can read diagnosis and repair of this problem. Beware that a short cycling well pump can damage the pump or its control switch.
when I flush the toilet my well pump cycles on to 70 lbs then right off and drops to 40 lbs and back on to 70 lbs then drops down to 40lbs and back on to 70 lbs it does this 21 or 22 times in a matter of just a couple of minutes then it stays at 40 or 39 lbs. I think it's doing this the whole time the toilet is filling back up? What would cause this?? - Jim Gale 10/17/11
what can be wrong with my well i put a new pressurer swithch the blader tank is good not lossing air but pump cut on and off ever two min what do i have to do to fix the problem - Anon 3/1/12
The pump is new and the pressure tank is old and the pressure switch is new. I run the water the pump clicks on and off every 10 seconds. I can see condensation line above the half way line on the tank. Whats the problem? - Rep 6/5/12
My switch cycles constantly and finally (sticks and holds contact. Is this an air pressure problem in my water tank? - Martin 7/19/12
My well is for outdoor irrigation only and has a very small (maybe 3-5 gallon?) bladder tank and pressure switch set-up.
When I turn on a hose the pump clicks on and then off immediately, just a few seconds then the water pressure from the hose dwindles down and then the pump kicks back on just for a second and right back off
so I get a burst of water then the dwindling again & it just keeps going like that. Isn't the point of the pressure switch & bladder tank to make the pump stay on while water is running, keeping the pressure constant?
What adjustment to the pressure switch should I make....increase or decrease the cut-on or cut-off point? - Jen 7/20/12
Reply:
Everyone above and Martin, I'm not 100% sure of course, but I don't think it's an air problem.
Short cycling of a water pump describes the pump turning on and off too often when water is running, but not a sticky or misbehaving pressure switch.
Burned switch contacts, a failing switch, a loose connection in the wiring, or a dirt-clogged sensor port on the pressure control switch base or in the tube that conducts water pressure to the switch are more likely at fault.
Martin when you swapped in the new switch, if you left a clogged tube on which the switch mounts or that feeds water pressure to the switch, even the sensor port on the new one could be blocked as well.
I'd also check voltage levels.
And that the pressure tank is not waterlogged.Jen when the pump turns on and then immediately off it's as if there is no air in the pressure tank - so as water is not very compressible, the system reaches cutoff pressure immediately.
If the irrigation system draws water fast enough, or if the pressure tank has an air charge, the symptom you describe should not occur.
Take a look at WATER PUMP SHORT CYCLING. I think your water tank may be waterlogged
my airbladder tank pressure came pre set at 38psi but the pressure switch is 20/40 is this causing the switch to cycle on off on off? second question, there does not seem to be water in the tank,why? i get water from the spigot with pressure and the guage jumps right from 20 to 40 and back again. why? - Patty 9/17/12
Reply: pressure tank [starting pressure at installation] should be 2 psi below the cut in pressure of the pump
Patty,
The pressure in the pressure tank should always be 2 psi below the cut in pressure of the pump. First, check the gauge when the pump first kicks in before shutting down the pump. Then, turn off the pump. Shut the water supply off to the pump, drain the pressure tank by opening the faucet furthest from the pressure tank, then release all the air from the pressure tank.Refill the tank with air to 18 psi if the pump is actually cutting in at 20 psi. When you turn the pump back on it will fill the pressure tank and will stop cycling unless you have a leak somewhere or dirty filters. - reply from WaterWorks 9/21/2012
On 2020-10-25 by BOB - good pressure then drops and go right up
When I run water in my sink I have good pressure then drops and go right up
On 2020-10-25 - by (mod) -
Bob that sounds as if your pump pressure control is not switching on when it should - perhaps it's debris clogged and needs replacement.
On 2020-09-07 by Ray - explain short cycling Zoller Air E Tainer Model 122
My system is short cycling with the pump kicking on after about a gallon of flow (Zoller Air E Tainer Model 122 - 33.4 gal, max working 100psi, precharge from factory 28psi, drawdown at 30/50 psi 10.3 gal) but I can't quite figure out how it's happening.
When I turn a faucet on the pressure drops from 68 to 38 as about a gallon of water flows then the pump kicks on and runs it back up to 68 in about 5 seconds (10 gpm rated pump) switches off and the pressure begins to drop again.
This has been going on for a couple of weeks (at least...just bought the house so it could have been longer). The tank is almost exactly 1/2 full of water (water level is obvious from temperature difference) so it seems unlikely there is a bladder/diaphragm leak.
There are no leaks in the system (pressure is rock solid at 65psi for 60 minutes when not running water and pump never comes on when not running water).
So, three questions. 1) could a stuck bladder/diaphragm be causing this?
Basically the system is behaving like the bottom half of the tank is filled with rocks and only has room for 1 gallon of water or the diaphragm can only move 1 inch instead of 10 inches but that would mean it's holding back a pressure differential of about 25psi which is a lot on 400 sq inches...seems impossible.
2) Should I turn off the pump and drain the water? I'm nervous because if the stuck diaphragm theory is correct that will make the pressure differential even higher with the demand side at 0 instead of 38psi. I'm in a very remote area and if the diaphragm tears it could take a couple of weeks to replace the tank...
3) Any other theories that explain the behavior I'm seeing?
On 2020-09-07 - by (mod) -
Ray
How are you determining that the water pressure tank has the proper air charge?
Also, perhaps you want an independent check of the pressure in the system. The pressure gauge as well as the pressure control switch can beome to blocked with debris and can act abnormally.
On 2020-02-14 by John - how long can a pump continue to short cyclone before damages?
I will be replacing my tank within a few days but the short cycling has been going on for a few weeks...how long can a pump continue to short cyclone before damages?
On 2020-02-14 - by (mod) -
That's a great question John and I don't think there's a single correct answer. A lot depends on whether a pump is running dry, and on the pump model brand and bearing design. In any case if the pump appears to still be working, once you've fixed the short cycling cause, you wouldn't replace the pump itself unless or until there was a sign of failure such as a bearing leak or inability to reach shut off pressure.
...
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