Water Pump Short Cycling Diagnostic FAQs

Q&A on how to fix a pump that cycles rapidly on-off

Definition of Well Pump Short Cycling

What pump on-off frequency or interval is considered "short cycling"?

I really appreciate your comments but am having a slight problem with terminology. Is the “cycle” of a well pump measured by the time from when it turns off to when it turns back on or the time from when it turns on until the time it turns on again? I have a bladder tank set at 40 psi/65 psi.

When I run three outside hoses it takes roughly a minute from when the pump shuts off at 65 until it turns on again at 40. It then takes about 4 minutes from when it turns on at 40 until it shuts off at 65, i.e., a total of five minutes between turn on’s. So is my cycle only one minute or is it 5 minutes? And in either case, does that sound like I’m likely burning out or shortening the life of my pump? Thanks much.

A follow up question to my previous one. In general, at what frequency of turn on to turn on ((i.e., from when it clicks on at 40, pumps up to 65, drops back down to 40 and clicks on again) do you start to worry about burning out your well pump motor or your switch? Every 2 minutes? 5 minutes? Etc. Thanks so much. On 2020-08-31 by Greg

by (mod) - Opinion: 30 seconds or less

Greg

At 30 seconds or less intervals between pump on cycles I consider that short cycling that should be addressed

Pump cycles every two minutes: what are normal well pump cycling on and off times? 20 gallon pressure tank.

So I had a pressure tank installed on my well today because the system of short cycling bad. I would turn the water on and it would go up to 50 PSI and drop down to 30 PSI and repeat every few seconds. The tank I installed is a 20 Gal.

Now when I run the water the pressure goes up to 50 in about 2 mins. and then down to 30 PSI in about the same time. Is this a normal rate?

or is there still a problem? I was under the impression this tank was suppose to keep that from happening. (Sept 14, 2012) M1helmethead

Reply:

M1

You are describing what sounds normal for a small sized water pressure tank.

To get a water draw-down time that is longer there are two approaches - choose depending on your equpment's capability:

1. install a larger capacity water pressure tank - 20 gallons is not much drawdown, but you won't want to do this having just installed a new tank

2. adjust the pressure control switch to widen the gap between cut-in and cut-out pressures. Just be sure not to set the cut-out to a pressure higher than your pump can maintain. For example, if you set the cut-in DOWN to 20 or 25 psi and keep the cut-out at 50 you'll get a longer draw-down cycle.

The draw down time for a properly-charged water pressure tank (with proper air pre-charge) depends on tank size, water pressure, and the flow rate out of the tank.

Short Cycling Pump due to Stuck Water Tank Bladder

Water Pump short cyles even with a brand new bladder type water tank

Just installed a new deep well water pump and new precharged bladder tank but pump is short cycling or kicking on and of again every few seconds. Can hear the pump turning the water used to prime it and both lines running to jet in well were profiled before hooking up the pump to lines . I am stumped as to what is causing this do you have any suggestions On 2019-02-14 by Gloria

by (mod) - check for and fix stuck water tank bladder

Possibly the tank bladder is stuck against the tank inlet and ban be freed by a brief higher pressure as long as you stay below the tsnks safe upper pressure limit.

Artesian Well Floods Water Tank?

Could an artesian well be putting water into the pressure tank even with the pump OFF?

My well supply water tank is 33 gallon 30/50, tank PSI at 28. The more I read the more I am getting confused.

Pressure drops to the cycle on after running faucets 2 minutes. When it is filling it takes 40 seconds to fill again. When water isn't used the pressure gauge is steady. So no leaks

The plumber stated older style bladder pressure tank switch, drained and pressure check was all good. However, as he was draining it he emptied 5 buckets of water and the tank was still draining.

Question is - is it possible that the artesian well with its constant flow of water could have been putting water into the tank even though the well pump power was switched off?

I believe that light switch is how to shut off the power to the well pump - right? On 2019-01-19 by bvorobel@yahoo.com

by (mod) -

BV

Thanks for an interesting question.

Certainly if you turn off power to the pump - as you indicated and as we see in the photo - then a flowing artesian well condition could continue to send water up to the pressure tank and building plumbing.

Some wells can temporarily function as a flowing artesian well (read about those by searching this site for ARTESIAN WELL) .

But "emptying 5 bucket of water" from a pressure tank isn't a decisive fact.

First: your water pressure tank is one that uses an internal bladder.

So there is NO reason that the tank should EVER need emptying. The bladder keeps water and air separated. Air doesn't get absorbed into water and air isn't lost from the tank unless the tank or its air valve or the internal bladder (one of those) is damaged or leaky.

The fact that your plumber was trying to empty an internal bladder pressure tank suggests inexperience or error.

If someone is trying to empty a tank like yours (which I said is not necessary nor useful) the air pressure in the water tank would make the tank continue to "empty" until pressure on the gauge and tank and system dropped to zero.

Your initial description of how your water system is operating does not sound odd to me except that the tank fills pretty quickly. That can be normal IF your submersible well pump is a powerful one and the well has great flow rate.

The tank air pre-charge of 28 psi is correct for a 30 psi CUT IN pressure control switch.

So in sum your system was probably working normally to start with.

Finally, you can rule out an "artesian well" as supplying water to your tank simply by turning off the valve (not shown , so I don't know if one is installed) between the supplying water line from the well and the tank itself.

but DO NOT do that if the pump is turned on as that could cause damage.

Turn off power to the pump

Close the valve

Drain the tank (for no reason as it's not necessary except for your own edification)

Notice that ultimately pressure measured at the tank drain or elsewhere in your home falls to zero and water stops leaving the tank.

At that point, IF you measured air pressure at the air pressure gauge on the tank top (under that little black cap on the right side of the tank top in your photo) you should see 28 psi of air pressure - that's the tank pre-charge pressure.

Close the tank drain.

Confirm the tank air pre-charge

Turn the pump on.

Done

Thanks so much for your information. You are the only one who made sense by writing in more layman terms.

Thanks so much for your information. You are the only one who made sense by writing in more layman terms.

I believe the large dial on the piping is a shut-off valve so you can stop the well water from coming into the house from the well.

The plumber couldn't shut that down so I am assuming the artesian well water flow was still entering even though he turned the submersible well pump power off.

The well pump is 1/2 hp and the well is only about 100 feet deep when they hit the spring.

The outside water gate ("faucet") at the top of the well pipe (14 Inches above ground) flows continuously (ALWAYS) with an air space of about 3 inches into another pipe that flows underground to a creek

. I am assuming that would be enough water pressure to continue into the house on its own volition without power. That is why when the plumber was attempting to drain the basement water storage tank water just kept running out of it. Thanks again. I think I will leave well enough alone. I was concerned about the 40 sec it took to fill the tank as being too short of a time.

And that tapping the outside of the tank didn't offer two different sounds like one part (top) being a hollow sound as far as I can tell.

Sometimes it seems like it an then again it doesn't. When it fills I can hear the movement of a balloon type sound or some type of movement. https://inspectapedia.com/water/Artesian_Flow_Disch_MI_050s.jpg On 2019-01-19 by bvorobel@yahoo.com

by (mod) -

BV

In your photo the green handled valve appears to be a shutoff between well piping and the pressure tank and switch.

It's common for an old, seldom-used water valve to fail to work when needed. It can be replaced by a plumber.

Your description of conditions at the well sound like a flowing artesian well.

You will want to read details at ARTESIAN WELLS, WELL SPOOLS inspectapedia.com/water/Artesian_Well_Spools.php

Your concern about a short 40-second tank fill time was reasonable- in that ***IF*** also the draw-down time in water volume and time before the pump turned on was also vey short - that would be "short cycling" of the well pump, described at

WELL PUMP SHORT CYCLING inspectapedia.com/water/Short_Cycling_Pump.php

where we give causes and cures.

BUT your case, driven by a (at least sometimes) powerful voluntary water flow out of a flowing artesian well is a different situation. The water tank re-fills so quickly because your well is sending water up to the tank at an unusually fast rate.

The movement and "balloon" expanding sound you hear may be the rubber bladder inside your water pressure tank as it expands and contracts.

Above (for other readers) is the illustration you were attempting to attach

Proper Tank Air Charge to Avoid Short Cycling

What's the proper pump air pre-charge pressure to avoid short cycling?

Our water pump runs short cycle recharge tank when drained water what should the pressure be and when filled what is its pressure to be for 40-60 ? (Nov 29, 2012) Jerry

Explanation by (mod): how and what air pressure to set in the water tank

With an empty tank and pump off the air precharge should be set to 2 psi below the cut-in pressure.

But

Watch out: it's not just pressure measured under any circumstances.

Properly your water tank must be empty when you set the air pre-charge pressure. - Daniel

 

Well or Piping Leaks vs Short Pump Cycling?

We hear hissing air leak sounds coming from the well and have no water

I can hear what sounds like a small air leak down in my shallow well and the pump will not run.I am wondering if I could have a bad foot value? We have just replaced the air tank,pressure switch and gauge.my well is only about 8 feet deep and has had a good supply of water for approximately 50 years.

please respond asap as I have been without water for 2 weeks and am very homesick. I'm on a fixed income and trying to figure all this out myself,with only help from a sister. (Feb 17, 2014) sue

Reply:

Sue,

I'm of course not sure what you're hearing but:

First: leaks anywhere in the water system can cause the pump to turn on and off even when nobody is using water. With a pressure tank that does NOT use an internal bladder (to protect against loss of its air charge) that can lead to loss of water tank air and then to pump short cycling.

Next: a hissing noise sounds like a leak somewhere.

Assuming you've got a one-line jet pump (which would work for a well just 8 feet deep) and the pump is above ground, with a simple foot valve at the bottom of your well pipe in the well,

THEN if you hear hissing I suspect that the pump is running but a leak at a pipe fitting connection or at a hole in well piping could be allowing air INTO the well piping;

Air in the line will cause air cavitation inside the pump body and the pump will run but not pick up water.

WATCH OUT: do not leave the pump running with no water - it can damage the pump.

As you just replaced the pressure tank I wonder: has your pump always been above ground? If so you can ignore my remarks below about snifter valves.

Start by using a good flashlight to look into the well casing: with the pump running you expect to see a single pipe in the well casing and from the above we expect to hear air entering the well pipe; but there might be something else going on.

Less likely, but you could be hearing air escaping from a bad snifter valve though I'd expect a snifter valve ONLY on a deep well with a submersible pump - search InspectApedia for "snifter valves" to read about that topic.

High Water Pressure Surging

Sudden water pressure surge to high pressure 80 psi and blew out a water pipe! Can't get pressure below 60 psi.

My water pressure suddenly went to 80 psi. It blew a water line. I’ve adjusted the pressure switch to 60-70 but cannot get it to drop below 60 psi. Is this due to a bad pressure switch? Thanks!(Apr 26, 2014) Dave Jones

Reply: repair procedure

If your pressure tank never goes below 60 psi do this:

1. Turn off power to the pump
2. Run water until no more water comes out of the tap
3. Check the water tank air pressure with an independent pressure gauge (your tank gauge could be stuck)
4. If the water tank air pressure is NOT 2 psi below your pump switch CUT-IN then release tank air to drop pressure to that point.
5. Set your pressure switch to a wider spacing such as CUT-IN at 40 psi and CUT-OUT at 60 psi or if you insisit on 70 psi then set the CUT-IN to 40 or 50 psi.
6. Adjust the empty water tank air pressure to 2 psi below the new CUT-IN pressure.
7. Turn the pump back on
8. Check the pump operation and tank pressures again

Diagnose our water pressure problems in Peru: pressure shoots up higher than permitted; how do I fix it?

I have a problem with the pressure in my water system and it is making a lot of pipes leak.

When the Pump starts the pressure shoots up to 5 bar and is designed to run at 1 bar. Can you tell me how to reduce the pressure. it is a fairly new system
Help please - (Nov 14, 2014) John Bickerton in Peru.

Reply:

Juan

Your pressure control switch may be improperly set, the pump may be over-sized, or you may need to install a pressure regulator on the house piping or at the pump outlet.

Short Cycling Pump due to Bad Motor Capacitor?

Short cycling well pump traced to bad start capacitor

My deep well submersible pump was short cycling, 4-5 seconds every minute or so. I changed the pressure switch but the problem continued. further troubleshooting revealed very high amp draw from the pump while it was trying to turn on.

The reason for this was the pump control start capacitor had burned out. The pump requires a "boost" of electrical energy to get started and run.

When the capacitor goes bad, the pump is unable to start and run, causing a high amp draw and short cycling. Replacing the start control box fixed the problem. Hope this helps. 7/23/14 M.H.

Reply:

M.H.

Thanks for the comment.

Usually short cycling is caused by a waterlogged pressure tank.

But some pump motors use a start capacitor that can fail - just as you cite.

Or a pump motor may be old, worn, and have trouble starting - needing a stronger, booster start capacitor.

See CAPACITORS for HARD STARTING MOTORS 

But because a waterlogged pressure tank can cause short cycling that can in turn damage pump controls or starting capacitor, or the pump motor itself, I'd double check that the pressure tank is not itself waterlogged.

Diagnose hot well pump motor, no water

I have a water pump that I don't use often. Today when I turned the water on I did not have any.

I check the pump and the motor felt warm to the touch. I disconnected the power supply and turned the shaft. I plugged it back up and it eventually started back pumping. It stopped again and I replaced the pressure switch.

It worked fine for several hours but now I have not water and the pump is not cutting on again. What could be the cause of this? (Oct 31, 2014) Anonymous

Reply:

Anon
Sounds as if the motor is seizing; you might try checking for lubrication requirements or for an impeller that is debris clogged.

IF the pump is removed and disconnected from power and the motor won't turn freely, replace it.

Short Cycling vs Finding Cause of Tank Air Leak

Short cycling farm well pump - couldn't find an air leak

Our farm well pump is short cycling when the water is run.

A constant pulse or surge.

It is supposed to cut in at 30 psi and cut out at 50 psi. However, the system shows 110 psi at the gauge. Turn the water on and it quickly drops to 80 psi where the pump cuts in and pegs the gauge, pulses between the peg and 100 psi until you shut off the water. Then it short cycles and settles at 110 psi. Although gauge shows 110 psi, water pressure appears normal..not 110 psi. I'm stumped.

Water pressure gauge shows 110 but I know pressure is not that high.

Also, the short cycling is a pulse or surge with constant clicking of the relay.

Reply:

Monte,

Watch out: That very high pressure is likely to exceed what your water pressure tank can safely handle. The risk is an exploded water tank or burst pipe that injures or kills anyone nearby and of course also there's a risk of pipe leaks.

Set the CUT-OUT pressure down to 70 psi or below.

The rest of your problem sounds like classic short cycling due to a water-logged tank and probably a debris clogged pressure gauge.

Try the diagnostic list at WATER PUMP SHORT CYCLING DIAGNOSIS TABLE

Monte replies: We also found that the pump starting capacitor seems to be corroded and leaking dielectric.

Moderator reply:

That s ounds like the pump needs repairs to start and run normally. Other readers have reported pump short cycling and having trouble starting when the starting capacitor for the pump motor is bad.

Monte Myers follow-up: damaged pressure gauge repair; tank lost air charge but don't know why

Dan,
The gauge face was bent causing the dial to spin on its' shaft. It wasn't clogged. I installed a new gauge. The tank had lost its' air. I added air and the short cycling stopped. However,I couldn't find any cause for the air loss.

Moderator reply:

Thanks for the update Monte.

Air may be lost from a pressure tank by absorption into the water passing through if the tank is *not* one that uses an internal bladder to keep water and air charge separate. Air can also leak out through a pinhole leak in a tank or from a leaky air fill valve.

Short Cycling Water Pump but Water Tank is OK

Pump short cycles but pressure tank does not seem water-logged

I have a Well Rite WR60 tank in my house system that was completely overhauled 4 years ago.
I'm experiencing short cycles and an extreme drop in pressure just as the pump is about to kick in at 40 psi.

First I replaced the 40 - 60 switch and no luck.

Then I checked the tank air pressure when drained and it was high - close to 50 psi.

Reset the air pressure to 38 psi and thing ran OK for about a week and then back to the short cycling and surging at cut in.

I've reset the air pressure several times but it never seems to last more than 4/5 days.

One thing that confuses me is that when I relieve the excess pressure there is no water coming out.
For what it's worth the tank is still under 5 year warranty but - probably pro rated ? 12/11/2014 Ron

Answer by mod: bad pressure control switch or water not entering water tank

Ron

Have you checked for a pressure switch that is not sensing water pressure due to clogging due not to the switch(which you replaced) but due to a clog in the small diameter tubing on which either the switch mounts or that conducts pressure to the switch sensing port?

Also have you confirmed that when the pump runs water is actually entering the water pressure tank? If not that could explain pump short cycling even though the water tank is "empty".

IF we find high air pressure in the tank after it's drained:

There could be a small leak in a tank bladder - in odd cases water leaks out of the bladder into the air space enough to keep pressure there abnormally high. If you think the tank is "empty" of water but it still feels heavy it may contain water.

I know we expect water to squirt out of the air valve when a tank is fully waterlogged, but it is possible for some water to be in the tank bottom but air still at the tank top (the water should be in the bladder not outside it in most designs).

I think of this as described by a few other readers as "pinhole leak in water tank bladder results in abnormally high air pressure creeping up in the pressure tank"

See PINHOLE LEAKS in WATER TANK BLADDER