How to Reduce High Pressure in Your Pool System

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There are several high water pressure scenarios that come up and for one reason or another have no apparent solution. You just replaced a failing motor or pump and your pressure jumped up from 10 to 20. Or your pressure crept up from 10 to 20 due to a dirty filter. You sprayed the debris off you filter cartridge like you did 50 times before but this time the pressure remained high. Or every time you turn the pump off, the back pressure is so high that it blows the cover off the skimmer or pushes the vacuum hose out of the suction port. This guide discusses these scenarios and possible solutions to correcting them.

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Step by Step

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Step 1

THE ISSUE - System pressure is generally measured at the filter pressure gauge. Most systems operate at around 10 psi or a little higher. Any reading over around 20 is considered high and operating at that level for a period of time puts a strain on your system's pump and filter. High pressure is generated by three conditions: 1- the system is trying to move a larger flow of water (GPM) than it can handle; 2- there is a blockage (BLK) in the system after the pump - from the pump's discharge port. 3- There is a suction air leak [AIR] before or at the pump that cause air to build up in the top of the filter tank creating back pressure.  In general  pressure leaks after the pump, do not cause pressure build ups.

Step 2

CLOGGED FILTER [BLK] - This is the most common problem leading to high pressure. Over time the creases of the pleats in the cartridge filter get embedded with fine debris, oils and chemicals. This embedded material will not come out with a simple spraying when you clean out the larger debris. We sell a cleaning product called "Cartridge Cleaner" which many people have found will eliminate this embedded material. One filter manufacture has suggested putting DE material into the creases of the pleats to help clean this embedded gunk out of the cartridge filter. Mix a 1# coffee can of DE in 5 gallons of pool water and pour the mixture into your skimmer. With the pump on, this action will coat the inner pleats of the filter.

Step 3

SUCTION AIR LEAK - This is the second most frequent cause of high pressure and back pressure. If you have a large suction leak, the pump will probably lose prime before pressure will build up. But is you have a small suction leak, air will be sucked into the system and build up in the top of the filter tank. Over time, sometimes hours, the back pressure will build up to the point. that it signficantly reduces the water flow through the filter and out to the pool. When the pump is turn off, this back pressure will surge back through the pump and skimmer. Some pool owners have seen a 2 foot water column shooting up though their skimmer cover from this back pressure. Look for leaks in any connections that you have recently changed.

Step 4

CLOGGED BREATHER TUBE [BLK] - Most filters have a breather tube to automatically purge air trapped at the top of the filter. This tube generally run from just under the top dome to the bottom of the tank. The breather tubes of some of the DE filters are integrated in the top manifold assembly and exit out through the discharge line. Air pressure in the top of the filter tank will build up if these breather tubes become clogged.

Step 5

OVERSIZED PUMP [GPM] - If you miscalculated your pump requirements, you may have a larger pump than your system can handle. Your pump is trying to push more water though your pipes and filter than they can handle so your system pressure goes up. This is also a common problem when people replace their pumps motor without regard for THP (Total Horse Power). Your motor's actual HP or total HP is the product of HP and Service Factor (SF). If you had a motor with a HP rating of 1.0 and a SF rating of 1.0, your motor's THP is 1.0. If you replace this with a motor with a HP of 1.0 and a SF of 1.5, you are replacing it with a much larger motor of 1.5 THP. If your pool was designed for a 1 THP motor, it may not be able to handle one with 1.5 HP. If the pipes and filter cannot handle the greater water flow, pressure will build up after the pump. When the pump is shut off this pressure (back pressure) will surge back through the pump, through the suction pipes and back into the pool. At this point you may want to replace your motor or a simpler (cheaper) solution would be to replace your pump's impeller with an impeller one size smaller. You can always put a smaller impeller on a motor. You just cannot place a larger impeller on the motor.

Step 6

CLOSED DIVERTER VALVES [BLK] - If you have diverter valves after the pump, you may have inadvertently closed off a section of your return lines. This action will restrict the total return flow and cause back pressure in your system. Open up these return lines.

Step 7

UNDERSIZED RETURN JETS [BLK] - One manufacturer has suggested replacing the return jets with ones with larger exit holes. This won't be as effective a change as something like changing your pump's impeller, but it should help.

Comments

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(1 to 40 of 152)

 Posted: 6/17/2019  Latest

How would I track down a suction leak. My issue sounds exactly like this could be happening
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InyoPools Product Specialist  Posted: 6/19/2019  Latest

How to Identify and Correct Air Leaks
 Reply

 Posted: 6/11/2019 

My pressure guage has a crack on the face where you would read the pressure. Would this cause high pressure?
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InyoPools Product Specialist  Posted: 6/14/2019  Latest

It would not.
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 Posted: 6/4/2019 

we are getting very low water pressure. I just noticed that the air relief tube has a hole in it. would this cause this problem? what exactly does the air relief tube do? Thanks!!
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InyoPools Product Specialist  Posted: 6/6/2019 

It releases air that is trapped in the tank of the filter.
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 Posted: 6/1/2019 

Hi, my psi when shut off is around 35-40. When i turn it on its 50. After 4 hrs of runnings its over 60 and the water from the return is slow. I back wash and it goes back to 35-40. The water is cloudy
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InyoPools Product Specialist  Posted: 6/6/2019 

Our obvious first question for you would be, did you follow each written step in this guide and exhaust the possibilities that they could be the cause?
 Reply

 Posted: 5/19/2019 

What does broken de grides cause im having fast pressure 10 to 20 in seconds
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InyoPools Product Specialist  Posted: 5/20/2019 

Broken grids dump DE in your pool. With the lost of DE, the pressure in the filter likely drops because there is less resistance to the water moving through the grids.
 Reply

 Posted: 5/20/2019 

Then why is it i can take filters out and it runs fine
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InyoPools Product Specialist  Posted: 5/20/2019 

By running fine, you mean it stays at a low PSI, that is because nothing is restricting the flow. Have you considered just replacing the broken grids? Besides the fact they are broken, if the problem goes away when you take the grids out of the equation, it sounds like you found the issue.
 Reply

 Posted: 5/20/2019 

Like to but broke
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 Posted: 5/16/2019 

We have a 16x 32 inground salt pool with a Hayward s220tc sand filter. Hayward pump sp3202vsp pump going into our 3 year. The pressure on the tank goes up to 30 psi right away when we run the pump. Running it on recirc, it read 7. Opened up filter and sand looks perfect, no lumps or clumping together. What else is causing the high pressure. Checked for air leaks and can’t find any nor do we see air bubbles after shutting the pump down.
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InyoPools Product Specialist  Posted: 5/16/2019 

Hello Tammey - It seems like there is an issue with the sand. The sand could be packed with oils and organic materials that don't flush out when doing a normal backwash. We'd recommend a product called Sand Aid. It breaks down that stuff and allows the water to flow through more easily.
 Reply

 Posted: 5/14/2019 

Pressure currently sits at 22psi. After backwashing which doesn’t seem to have much gunk, pressure is unchanged. When I release air from pressure valve, the water is a slow stream, not the usual gush of water. Any ideas for high pressure but low pressure water output of out of air relief valve?
 Reply

InyoPools Product Specialist  Posted: 5/14/2019 

The filter media could be clogged with oils and other substances that don't backwash easily. If you have a DE filter, try soaking the grids in a filter cleaner. If you have a sand filter, try a product called Sand-Aid. It will help remove those oils so that the filter can operate better. Another possibility is that the pressure gauge is bad.
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 Posted: 4/26/2019 

Just replaced entire filter after replacing multi port valve in December. Backwash provides no “gunk” (it seems clean) but pressure is high, 20 or so, and jets don’t push water when on filter setting of multi port. No problems when on recirculate with water movement and skimmer collection. Any ideas? I was originally thinking a clogged main drain may be my problem, but I’m starting to think otherwise as recirculation is working.
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InyoPools Product Specialist  Posted: 4/30/2019 

Hello Will - If recirculation is working, the problem is likely the filter media. What type of filter do you have? Make and model?
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 Posted: 5/12/2019 

I actually have the same problem as the OP. I installed a new DE Hayward Pro Grid filter this season. I chose the 24 sq. Ft model based on feedback from intheswim. My pump is a Hayward Super Pump VS Variable Speed. My pool is 16000 gallon in ground. Once I backwash the filter, the pressure is fine. Actually the pressure is always fine but the return to the pool, the pressure decreases dramatically within five hours . I backwash again, everything returns to normal . I’m afraid I bought an undersized filter.
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InyoPools Product Specialist  Posted: 5/14/2019 

Hello Ed - The Hayward Pro Grid 24 sq ft filter can handle a 16,000 pool. Is the pool clear or is it cloudy/green? What is the pressure gauge reading when the filter is clean and what is the pressure reading when the flow from the jets slow down? Are there any air bubbles coming out of the jets?
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 Posted: 6/21/2018 

Hello Marshall - You may have a suction side air leak. Check out our guide titled "How To Identify and Correct Air Leaks". If it were a leak on the pressure side, you'd see water leaking while the pump is running.
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 Posted: 6/19/2018 

I just replaced by cartridge filters as I have many times. Turned it on and everything seems to run well, except when I turn the pump off I can see air flow into the basket filter through the clear lid. Air flows in until its almost empty. I don't see any water leaks in the lid when the pump is on.
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 Posted: 5/26/2018 

This is an awesome explanation.
 Reply

 Posted: 1/6/2018 

I have a cartridge filter and it runs great for a couple hours, but then the pressure starts rising and my pool vacuum stops moving (when connected to suction port). The pump primes fine and there are no air leaks. But, If I connect the vacuum to the skimmer, the pump doesn't prime fully (the pump basket doesn't fill with water) but the pressure stays normal and the vacuum works great. I only have the suction port and skimmer open. I believe the other line is a main drain? and it always remains closed. I've tried everything I can think of and followed all of your guides and I don't know what else to do. What could be wrong? Thanks.
 Reply

 Posted: 7/24/2017 

Denis E - Thank you very much for your feedback !
 Reply

InyoPools Product Specialist  Posted: 7/24/2017 

Anonymous (high pressure) - Look at steps 3 and 4 of this guide. Does your water surge backwards when you turn your pump off? If you just relieve the air pressure at the top of the tank, does your pressure drop to 10 and then slowly creep up to 30 over the next couple of days. If so, you may have air pressure building up in the top of your filter tank due to suction air leaks. See our guide on "How to Identify and Correct Air Leaks".
 Reply

Anonymous  Posted: 7/23/2017 

I have a cartridge filter system and as soon as I clean it it goes down to abut 12 psi but more and more I have to clean the cartridge or it will be close to 30psi. The system is only 3months old.it's getting to be every couple days I have to clean it. My vacuum won't work when the psi goes up.
 Reply

 Posted: 7/19/2017 

Replacing the return jets with larger exit holes brought my 16psi brand new sand filter to 10psi. That's a huge drop. I had a smaller exit hold on my old return jet so I decided to change it with a larger one and it worked great.

P.S.
I just installed a brand new pump and sand filter when I replaced my return jets.

 Reply

InyoPools Product Specialist  Posted: 7/4/2017 

Jerry Shannon - The extra piping and heat pump should not have had that much effect on your water pressure unless you inadvertently closed off some of your piping. Do you have a bypass path around your heater that could isolate your problem to the heater or new piping? Also, most heaters have a bypass within the heater for when the heater is off. That bypass may not be working properly.
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InyoPools Product Specialist  Posted: 7/3/2017 

Pat H - There is an Air Release Assembly that runs up the center of the tank to relieve air that might collect in the free zone between the sand and the top of the tank. See an example in Blue Wave SandMan 18" & 22" Filter (number 5a,b). Make sure that tube and top screen are unclogged. If that doesn't solve your problem, see our guide on "How to Correct Low Water Pressure in Your Pool System". Check Step 6, Clogged Impeller, first.
 Reply

InyoPools Product Specialist  Posted: 7/3/2017 

Joanne - If your pressure was over 30 psi, you may have a high pressure problem with your system. However, I would guess that your pressure gauge was only partially screwed on or defective. I would get another one and make sure it is screwed on all the way. Also, I wouldn't move the pressure gauge when the pump is on.
 Reply

 Posted: 7/1/2017 

Have a Blow Molded sand filter with auto air pressure relief valve.
There is not enough air pressure in the system. There are no leaks
I have installed a new "O" Ring. Where is auto air relief valve located? Can this problem be fixed?


 Reply

 Posted: 7/1/2017 

I have an self cleaning pool system. I went out and looked at the pool and it didn't seem like the water was moving around much. I went over to the filter to look at the pressure meter and I turned it so I could see it and the whole thing blew off.....the plastic piece even came off the face of the meter. I shut the filter off. I want to know what do I have to do now? Can I just go to the pool store and buy another meter and screw it on? Not a dumb question here...just someone that doesn't know much about pools and the workings of one! :(
 Reply

 Posted: 6/30/2017 

I have a 21x41x54" oval above ground pool. Pump and filter came with the pool. A hayward matrix 1.5hp pump and a hayward sand filter. I re-plumbed with 1.5" plastic pipe when I added a Heat Pump. pressure went from 15 psi to 30psi and stays there. Did the extra plumbing and adding diverter valves for the heat pump raise my filter pressure?
 Reply

InyoPools Product Specialist  Posted: 6/30/2017 

Pat - If your gasket (O-ring) has "wavy" parts, it sounds like it is stretched and should be replaced. A stretch O-ring tends to overlay on itself and leak.
 Reply

InyoPools Product Specialist  Posted: 6/29/2017 

LynnH - I don't understand your comment about your vacuum never catching suction. Does your vacuum not have sufficient suction to suck up water? If you have water blasting our of you jet, I would think you'd have move water flow than you originally had which should provide more than enough suction. Could you have shut off any of your return diverter valves - like to a water feature. Also, check that your cartridge was seated completely into the bottom of the tank.
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 Posted: 6/29/2017 

I bought a new house last year with an inground pool running a Hayward EC65A D.E. pump/filter. I've had the high pressure issue (20psi or so). I took apart the filter last night to wash out the fingers and noticed my gasket had some "wavy" parts to it. When I turned the filter back on, the water flow back to the pool was great, much better than before. This morning the psi was back around 20 and there was little flow. I do see a few spots where there is water dripping from the top of the filter canister. Does my gasket need replaced or could it be something else? I didn't clean the fingers with any solution as I didn't have any so that probably still needs to happen.
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 Posted: 6/27/2017 

Hi - first of all, thank you for all these answers, what a great resource! I am having a problem I can't figure out. I cleaned my cartridge filter recently and, as expected, the pressure on the gauge went from close to 20 down to about 12, which is what it always does. However, instead of the normal improvement in water pressure coming out of the jet, the water is just BLASTING out. But the gauge still reads around 12, so the overall pressure is not high. I can't even hook up my vacuum - it never "catches" suction. Do I have an air leak somewhere? Where could it be? It just seems odd that the pressure is not high at the gauge, too. Thanks in advance!
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InyoPools Product Specialist  Posted: 6/27/2017 

Yassr - I would guess that sunscreen oils and chemicals have built up into the folds of the filter (assuming they are cartridge filters) which is starting to reduce the flow through the filter. Try cleaning the filters with a solution of TSP.
 Reply