Water tank pressure creep-up:

This article describes the causes, effects, diagnosis & repair of slowly-increasing pressure in an internal-bladder type water pressure tank. It can seem very odd for tank pressure to increase above it's pre-charge or pump cut-off pressure but believe it or not it can happen.

The usual cause of un-planned water tank bladder pressure increase is a small leak that lets water into the tank's air space. Ultimately you'll need to repair this problem to stop pump short cycling or other weird water pressure behaviors in the building.

Diagnose & Fix Mysterious Increases in Bladder Type Water Tank Pressure

Reader Question: water tank pressure creeps up and water pump short cycling: pinhole tank bladder leak symptoms?

(Oct 18, 2014) Rick said:

I have a 20 gallon diaphragm tank the air pressure goes from 28 to 40 psi in about 24 hours after I drain the water and reset the air pressure and starts short cycling.

Sounds like a pin hole in the bladder after reading your articles right.

8/10/2013 D.S. said:

First off, great site with tons of information! I don't have a question so much but wanted to submit an issue I had and the resolution as it was a bit different than anything you have listed. IF you choose to use this information on your site, feel free to edit as you wish.

[At your general page on water pressure tanks found at WATER TANK: USES, TROUBLESHOOTING, I was reading about tank pressure problems and short cycling water pumps.]

We have a Amtrol Well X Trol WX-250 (44 Gallon Pressure Tank) which is about 14 years old. 40/60 Pressure Switch on our well. We noticed the well was cycling too fast. We should have a drawdown of about 11 gallons. We were getting a drawdown of 2-3 gallons.

Followed the procedure assuming I would find a waterlogged pressure tank. Cut power to pump, open valves to drain water from system. Air gauge on the tank. I should get 38 if all is tuned right maybe less if the bladder is shot. The reading however was 52 PSI. That is odd. This reading was with a dial tire gauge. Try a digital one that I have 53 PSI.

After talking with a friend who is a plumber with 40 years experience he was stumped. The only thing I could figure out is that there is a small hole in the diaphragm allowing water to leak past to equalize the air chamber with the pressure of the water (60PSI). Never have noticed air coming out of any fixtures.

So I bled off the pressure to bring it down to 38 PSI expecting to get water out of the valve in the process. No water found and tank was set to 38. Turned everything back on and things were better but I still didn't think I was getting 11 gallons of drawdown but noticeably better. Ran the system 48hrs and repeated test.

Again, cut power, drain the system and pressure test. This time I got 45PSI. How could it rise 7 PSI in 2 days?

Call the plumber but he was busy with another customer so while waiting to hear from him I call Amtrol tech support. Explain what I am seeing, what I have done as described above. The tech stated that I have a small hole in the diaphragm just like I had thought was the only plausible explanation.

I asked what options I have and he said tank replacement. He commented that this issue is one they have seen before but is one that they had a hard time figuring out for a while as the symptoms are not what is normally expected. Pressure high not low, no water from pressure valve when venting air. He stated that the tank was getting water logged but basically we caught it early in the failure process. So it had not totally failed yet.

So new tank installed and everything is back to normal. Once the old tank was removed it was quite heavy as it was getting water logged. I used a tool to remove the core of the valve to fully vent all pressure from the air chamber.

Never got any water out. Finally I tipped the tank over to see what happens and at that point I started getting water out of the tank. So it was getting water logged as the tech mentioned it was just early in the failure process.

The main reason I wanted to write you is because everywhere I looked (this site and many others) described the normal failure symptoms. Low pressure and possible water from the air valve. Another possible symptom is high pressure though. It makes sense. The air chamber should be sealed. As long as the pump is off and water drained it should be 38 or 2 lbs below cut in as your site mentioned.

If it is anything different (high or more commonly low), either it was set wrong during installation or the diaphragm has a hole or is ruptured. If it is different, adjust pressure to where it should be and run it for a couple days and check again. If the pressure changes again, odds are the tank is bad.

Thank you for setting this site up and the work you do. - D.S. 8/10/2013

Reply:

Thank you for the interesting water pressure tank water-logging and "high pressure" report - it helps us realize where we need to work on making our text more clear or more complete. A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer than we can give by email alone.

And I suspect that in the case you describe, we could have missed something to complete an explanation of the system pressure readings you observed. But with what you've said I can offer a possible explanation that fits the facts as given.

If the pressure control switch on a water pump system is working properly, the system pressure will never exceed the pump pressure control switch cut-off pressure. Your pump cut-off pressure was 60 psi using a 40/60 pressure switch. The highest pressure you recorded at the tank was 52 psi - consistent with this rule. Amtrol posed that there was a small leak in the internal water tank bladder.

This makes some sense to me and leads to speculation about what' was happening in your system.

Why would water tank pressure readings creep up in just a few days?

You asked how the apparent tank pressure could "creep up" above the cut-in pressure over several days.

I agree that the explanation probably lies in one of two areas:

1. a faulty pressure control switch OR
2. a leak in the pressure tank's internal bladder.

Debris clogging can cause a pressure control switch to properly sense lower pressures, failing to turn the pump on consistently, but debris clogging at the switch does not normally cause tank over-pressure. This does not sound like the situation you describe.

Other internal bladder type water pressure tank odd behavior can be caused when a bladder sticks to itself - often causing very small draw-down volumes as water cannot enter the tank. This too does not sound like the situation you describe.

An explanation for the unexpected increase in water pressure in the tank combined with shortening draw down cycle may be that water under pressure leaks out of the bladder into the space between tank and bladder through a small leak or opening.

Because the hole in the bladder is so small, it is quite possible to turn on water in the building and receive water at a lower pressure and quantity than normally delivered from the pressure tank because the rate at which water under higher pressure could leak back into the bladder interior would be very slow.

In addition, water accumulating in the air space outside the bladder reduces the volume of that air space, thus reducing the draw-down water quantity and leading to short cycling.

Effects of a pinhole or small bladder leak in a water pressure tank

Re-stating what I think is going on, at the upper end of water tank pressure range that occurs during each pump-on cycle, some water is forced out of the water-containing bladder into the space between the steel tank and the bladder where it accumulates. The ability of water to return to the bladder interior may be less than its ability to leak out of the bladder due to the position of the particular pinhole or small leak.

That is, leakage tends to be unidirectional, pushing out of the bladder into the air space only at the top of the pressure cycle.

The result of water accumulating out of the bladder and in the space normally occupied by air in the pressure tank is that the volume of air-space is gradually reduced, leading to short water pump on-cycles just as occurs in a bladderless water pressure tank that has become water-logged.

Why no water came out of the air valve at the pressure tank top

Why, then might you have not been able to get water out of the leaky pressure tank through the air valve (as occurs in a water-logged bladderless tank)? Water has to be trapped within the tank's air space; the air valve is at the top of the tank. Water in an upright tank will be at the tank bottom.

Opening the air valve, even releasing all of the air pressure remaining in the tank will still leave water in the tank air space at the tank bottom. Upending the water tank might seem a course that would allow water to drain out of the air valve, but keep in mind that if there is no other way for air to enter the tank during this process, it will be difficult to drain any water out.

Here is a similar example; if we want to drain water out of a water heater tank, the tank drain, located at the bottom of the tank is opened.

But unless we open a valve at the top of the water heater tank (often we use the relief valve for this purpose), because there is no path for air to enter the tank except through the same valve that is draining water out, the rate at which water leaves the water heater tank is very very slow.

Water drains out at a dribble until enough vacuum is created inside the tank to stop water leaving and instead draw a gulp of air into the tank. Then more water dribbles out. This is a very very slow process occurring through the 1/2" diameter tank drain valve opening.

Now translate this situation back to an "upside down" water pressure tank trying to drain water out (and let air in) through the 3/16" diameter air valve opening. Little or no air can enter and little water will thus drain in out except at a very slow rate.

[It is also worth noting a condition that probably was not occurring on your system: in some situations we are measuring or sensing tank pressures differently at the pump control than at a tire gauge used at the air valve.

The air valve location senses air-pressure in the air space around the bladder, while the pressure gauge senses water pressure in the piping system - under normal circumstances that includes water pressure inside the bladder. In a normally-operating system these pressures (air and water) should be the same; but if a bladder is damaged and sticking over the water outlet, that pressure consistency might be lost.]

Reader follow-up:

Based on the water pressure gauge I feel that my 40/60 pressure switch was operating properly. When replacing the pressure tank I also replaced the pressure switch, connecting pipe for it and pressure gauge. These items are pretty in expensive to they were done as preventative maintenance as I don't want to go back and address these other items in a few months or so.

The pressure gauge was showing signs of sticking as it was dropping once it got to about 50 PSI. Of course the pressure gauge had nothing to do with the operation of the pressure switch other than provide feed back as to what pressure the water is at in the system.

One symptom that may be worth mentioning is that when I shut off the power to the well and opened a drain valve next to the pressure switch to drain the system I also opened a faucet in the laundry room 10' away from the pressure tank as well as a bathroom faucet upstairs. This was done to try and drain the water from the house pipes the one upstairs opened to allow air in to speed things up.

Like you mentioned in draining a water heater. So what I saw that may be worth noting.

While that valve was open, I did still see a trickle of water coming out of the valve at the pressure switch. I attributed it to water draining back from the house.

However in my case it may have been water leaking from the small hole in the waterlogged pressure tank. When I disconnected the tank it was quite heavy (compared to the new one) and it continued to drain water very slowly from the tank even though the core of the air valve was removed.

Also when I tipped it over it did drain water from the air valve. This is shown in the photo that is attached. Of course one would have to be certain that any trickle from that valve is not coming from the house plumbing as it is draining to the low point in the system.

I suspect that I didn't get any water from the air valve when venting air from 52 back down to the proper level of 38 because as you mentioned the air valve is at the top of the tank and it appears that no air never left the tank (via plumbing) other than what I vented explaining the high pressure.

Because of this head space the water never reached the air valve when venting while it was hooked up. Once I could tip it on its side then I could get water to exit from the air valve. - D.S. 08/11/2013

Reply:

I think you've got it just right. As long as water in the pressure tank bladder was pressurized and unable to exit at a tank drain, when the water tank is removed and placed upside down or on its side with the air valve facing down, pressurized water in the bladder might indeed slowly leak back out of the (stretched) bladder, into the air space of the tank and out of the air space slowly through the schrader valve.

And I agree it's much cheaper to replace old plumbing parts during a water tank replacement than to have to re-visit the the topic later.

Thanks for the photo of your water tank. - DF

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-01-26 by (mod) -

NO, Andrew you don't need water in the tank before adding air.

With NO pressure on the system (pump off, pressure drained) set the air pre-charge to 2 psi below the CUT-IN pressure.

See details at

WATER TANK AIR, HOW TO ADD

On 2021-01-26 by Andrew

I got a tank do i have to have water in tank before adding aire in tank [Photo above]

On 2021-01-04 - by (mod) -

That's what it sounds like to me too.

Watch out, exceeding the pressure rating of a tank is very dangerous because if the tank ruptures anybody nearby could be badly hurt or worse.

On 2021-01-04 by Rich

With well pump on the pressure gauge pegs and relief valve opens up. Could it be the pump regulator not turning the pump off when pressure of 40 psi is reached?

On 2020-09-16 - by (mod) -

Could indeed be one of the causes discussed above.

On 2020-09-15 by Malcolm Plager

Pressure switch and WX250 pressure tank were replaced with the well pump in 1989. All have been in operation in our home since. Recently the 40/60 pressure switch was replaced. Pump comes on at 40psi and goes off at 60. All should be okay, but then the pressure gauge starts to creep up and shows an increase to 70psi. Another symptom is we also get random loss of pressure, loss of all flow of water for a few seconds, and then it all comes back on and operates normally. Checked the pump cycle time, it’s a Gould 7GS10 and it’s okay even though it’s been operating for about 21 years. could the increase in pressure and the random loss of all water be caused by the pressure tank starting to fail with a “small hole in the bladder?

On 2020-08-01 by Tom

My well pump kicks off in the middle of running water then comes back on in a couple of minutes. We have plenty water in the well, so I thought maybe I had a hole in the line between the pump and the house because I am getting air in the lines after the pump goes off and back on. I checked the air pressure at the top of the storage tank and it was 49 PSI so bled it down to 38psi worked better but then a day or two same thing increased air in the tank. Bad storage tank?

On 2020-06-14 - by (mod) -

Sabrina

Thanks for asking; no, a pump that cycles every 4 seconds is "short cycling" usually due to a water-logged pressure tank.

Details about how to diagnose and repair this are at WATER PUMP SHORT CYCLING - home

On 2020-06-14 by Sabrina

Just wondering . One day I turn the water one and we have no water . ( moved to the country, with well) so my father in law come and changed the control box for the pump cuz the start capacitor blew . 2 years later (today) it blew again . So husband changed it again and it blew when he went to fill the pool . So went out got a new Control box and a presser switch . Now that he has changed that it’s cycling like every 4 seconds . Is this correct? Do I have more problems like my pump is fried ?

On 2020-01-25 - by (mod) -

Mike

Thanks for the helpful comment about water pressure tank pressure that seems to magically increase on its own. I agree that this can be tricky to diagnose, and was lucky to come across enough cases to realize the likely cause - just as you found.

For other readers, what's happening, using Mike's tank as an example:

In an internal bladder tank the air pre-charge is in a space above a rubber bladder into which water is pumped - the air and water are intended to be kept separate, thus avoiding absorption of air into water and loss of the tank's air charge over time.

- the water pressure tank was pre-charged properly to about 2 psi below the pump control switch CUT-IN pressure, so it was pre-charged to 36 psi.

- a pinhole or at least a tiny leak develops in the bladder.

- when the pump has pumped the tank to a pressure above the pre-charge, that is at any pressure higher than 36 psi in this case, a bit of water leaks through the bladder pinhole and into the air space where water isn't supposed to be.

- That water reduces the physical space in the pressure tank's pre-charge area. When we have a gas (air in this case) in a fixed space at a given pressure (say 36 psi) and then we make that space smaller, the pressure of the gas (air) will increase proportionally.

Volume-1 x Pressure-1 = Volume-2 x Pressure-2 is the simple formula for a gas under pressure in a container. So you can see that if Volume 2 is the new volume, and it got smaller (that air space over the bladder got partly filled with water) them P2 has to increase so that the whole calculation remains the same as original V1xP1.

- The effect of water leaking through the bladder into the air space in the pressure tank is thus an increase in the lowest pressure that the tank will see during pump on-off cycles.

- The effect of that mysterious pressure increase in the tank is ultimately water pump short-cycling, cutting on and off more and more frequently.

Thanks again, Mike, let me know if this explanation sounds right or if you have suggestions.

Daniel

On 2020-01-25 by Mike

Had a similar situation. Thankfully this was the first site to address self increase in a pressure in well water pressure tank. I have a 1/2 hp submersible pump and my house is supplies with a 20 gal. Well Rite pressure tank that is 11 years old. Cut in pressure:38, cutout :62. I had tank charged at 35/36 psi. 6 months ago I noted my tank pressure had gone up to 40 psi. I checked friends who suggested a pinhole in bladder or hardened bladder due to high iron and manganese in water. I thankfully am picking up a new diaphragm tank day after tomorrow. I noted recently pump taking a bit long between cutin and cutout. I checked tank pressure today and there it was back at 40 psi. I wish I had changed the tank sooner but luckily for me it appears to have likely been a slow leak. I like the site. Lots of experienced people out there.

On 2018-12-12 by (mod) -

In the ARTICLE INDEX at the end of the article on this page you'll see your serious of diagnostic articles on well pump short cycling that will help you sort out the problem that you described. It's not likely to be a problem with the pressure control switch itself. More likely your water tank is waterlogged.

On 2018-12-11 by Steve

My Tank is only 3 years old..... It started short cycling.... I removed pressure switch and cleaned.... still creeps up after a few days....is it a pinhole? or should I start replacing other stuff Thanks

On 2018-08-12 by (mod) -

GP

Thank you for the nice note. We work hard to provide authoritative and un-biased information so I'm really grateful when a reader finds it useful.

Questions, criticism, and content suggestions also help us out. So if you find an InspectApedia article that leaves you with questions, don't hesitate to ask. - Ed.

On 2018-08-11 by gpaCook

Just a thanks for the article. I just ran into the identical problem originally described by "D.S." on 8/10/2013, including 40/60 pressure switch, and reading 52 psi when doing the bladder pressure test.

I also bled the air down to 38 psi and operation appeared normal. But I did not check draw down, because family needed water before I finished reading the article and understood what was going on. I had no idea how this was possible, but now I do. Thanks again.

On 2018-07-03 by (mod) - very long pump-on cycle may damage bearings

More, except for a pump rated for continuous duty, it's likely that when you leave pumps running for protracted period such that there is a risk of running out of water, the pump bearings can be damaged and the pump could need repair or replacement.

I don't see that situation damaging the pressure tank. What would damage the pressure tank would be an improper pressure control adjustment such as you subjected the tank to pressure beyond its rating. That would be dangerous. The tank could burst and injure someone.

On 2018-07-03 by Lynne

Our water has been left on outside for long periods of time several times. the pressure tank and control box had to be replace. can leaving the water on when the pumps etc. have to work overtime cause the damaqge to the pressure tank?

On 2017-09-26 by tutor

can i install a pressure tank upside down my old one was,

On 2016-11-12 by Anonymous

Why does my air valve drain water from tank

On 2015-09-06 by (mod) -

Bradley and Willie: the article WATER TANK PRESSURE SELF-INCREASE describes how air pressure can increase in a water pressure tank - some of these causes can be a bit surprising such as an internal bladder leak that is "one-way" letting water into the air space of an internal-bladder type pressure tank, or a misbehaving air volume control snifter valve system used on submersible well pumps. If you have questions about the clarity or completeness of that text please let us know.

It may help with diagnosing a water pressure tank that does *not* use an internal bladder to realize that if there were simply excess air in the tank from over-dosing the air in the tank at installation, it will typically show up as air discharge at nearby plumbing fixtures. But a persistent air leak in such as in well piping or from gases in the well can mean that such air discharges are recurrent.

On 2015-09-06 by Bradley

I adjust the air pressure in the holding tank to 2psi below pump kick in and it maintains for about a week or two and then the air pressure increases in the tank and the pump runs short cycles. When I check the air in the holding tank it increases to about 50psi at pump kick on. A hole in the bladder would not cause this would it?

On 2015-05-26 by willie

Why does air pressure increase in the well tank?" I set the tank air pressure at 20psi, cut-in 30psi, cut-out 50psi the unit cut off at 50psi I run the water the pressure get down to 20psi and trip the breaker, I check the pressure in the tank it reads 38psi I deflate back to 20psi shutting all water off, start the pump the pressure increases to 50psi and cycle off turn the water on pressure decreases I check tank press. tank press.

again increase so I adjust it down to 28psi when system press. reach this point it cycle back on, if no adjustment here the system would have tripped the breaker again. I am reading that there is a pin hole in the bladder and this is a NEW TANK purchased 05/21/15 O/N S1904967.002 What to do?

Reader Question: how does water leak into the air space of a bladder type water tank?

AUTHOR:Anonymous or Jim: (no email)

You say water leaks into the tank air space to cause increasing tank pressure. How is that possible without water coming out of the tank top air valve?

COMMENT:If, as you say early on that "air pressure and water pressure inside the tank will be at the same psi", how does the pressure rising at the air valve indicate a pinhole leak in the bladder? Thanks Jim

Reply:

Anon/ Jim:

it's not what I say, it's basic laws of physics. But I agree with you that the article above needs clarification.

IF air is outside the bladder and water leaks into that air space, it can only enter hat air space when the water pressure is above the initial air charge pressure of the tank when installed. That initial or pre charge pressure, if measured with no water in the tank, will be set at 2 psi below the pump cut in pressure. As water leaks into the air space it reduces the available space for the air.

Thus if pressure is measured just at the point of pump cut-in, the pressure *at that time* will read above the original tank Pre charge pressure. You'd only see that if you measured at pump cut in. Later the tank air and water pressure will be higher - up to the pump cut off pressure.

Eventually enough water leaks into the air space that the pump short cycles.

What this case might let us distinguish is a pinhole bladder leak from a ruptured bladder. The latter can show up as a period of air at faucets, then short cycling pump, and then water squirting out of the air valve if it is opened.

More generally, Higher pressure at the air valve means higher pressure in the tank and at the air valve. So we should have made clear the point in the pump cycle when you can see air pressure as elevated is at or close to pump cut in time. And the higher pressure is only in relation to the original Pre charge air pressure.

Measured later in the pumping cycle or at pump cutoff, air and water pressure will of course be one and the same.

I suspect this effect can't be detected so easily later in the life of the bladder leak.

If water is leaking out of the bladder, the effects include pump short cycling and ultimately water squirting out of the air valve if it's pin is depressed.

Thanks for asking, let me know if this is still unclear.

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Continue reading at WATER TANK BLADDER PRESSURE ADJUSTMENT or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• WATER PUMP SHORT CYCLING
• WATER TANK AIR, HOW TO ADD
• WATER TANK BLADDER PRESSURE ADJUSTMENT
• WATER TANK BLADDER REPLACEMENT
• WATER TANK BLADDER STUCK to ITSELF
• WATER TANK PRESSURE SELF-INCREASE

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