How to Reduce High Pressure in Your Pool System

WRITTEN BY:  Inyo Pools

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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.


Step by Step


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.


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Inyopools  Posted: 06/21/2018 17:09 PM  Inyo Product Specialist

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.

Marshall Pickett  Posted: 06/19/2018 20:19 PM 

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.

Jeff  Posted: 05/26/2018 8:40 AM 

This is an awesome explanation.

LM  Posted: 01/06/2018 15:53 PM 

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.

dinyopools  Posted: 07/24/2017 16:28 PM 

Denis E - Thank you very much for your feedback !

Inyopools  Posted: 07/24/2017 16:23 PM  Inyo Product Specialist

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".

Anonymous  Posted: 07/23/2017 15:37 PM 

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's getting to be every couple days I have to clean it. My vacuum won't work when the psi goes up.

Denis E  Posted: 07/19/2017 10:08 AM 

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.

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

Inyopools  Posted: 07/04/2017 12:42 PM  Inyo Product Specialist

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.

Inyopools  Posted: 07/03/2017 12:25 PM  Inyo Product Specialist

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.

Inyopools  Posted: 07/03/2017 9:40 AM  Inyo Product Specialist

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.

Pat R.  Posted: 07/01/2017 11:44 AM 

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?

Joanne  Posted: 07/01/2017 11:34 AM 

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! :(

Jerry Shannon  Posted: 06/30/2017 14:19 PM 

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?

Inyopools  Posted: 06/30/2017 13:27 PM  Inyo Product Specialist

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.

Inyopools  Posted: 06/29/2017 11:03 AM  Inyo Product Specialist

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.

Pat  Posted: 06/29/2017 9:04 AM 

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.

LynnH  Posted: 06/27/2017 19:43 PM 

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!

Inyopools  Posted: 06/27/2017 15:16 PM  Inyo Product Specialist

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.

Yassr  Posted: 06/26/2017 23:03 PM 

Hello . I have a pool of 8 filters that was operating probably for 2 years normally , but suddenly pressure go higher over 20 psi whenever i try to turn 5 filters or more pressure gos higher over 20 psi
Q.what my is happening?

Inyopools  Posted: 06/26/2017 15:21 PM  Inyo Product Specialist

db - I assume that your return hose is the AG hose from your filter to the pool that returns water to the pool. If you have upgraded your pump's HP significantly, the regular return hose may not be designed to handle the added pressure. If you can't get a heavier hose, you might consider plumbing the return line with PVC pipe.

Celine  Posted: 06/25/2017 10:07 AM 

You are awesome...

db  Posted: 06/24/2017 19:48 PM 

My return hose spings leaks like a sprinkler . I have replaced it four times. Brand new Hayward pump and sand filter operating at 18psi. Thanks for any suggestions

Inyopools  Posted: 06/19/2017 17:26 PM  Inyo Product Specialist

Pam - It takes a lot of pressure to blow a hole in a PVC pipe. Did you have any indication of extremely high pressure? How large is your pump? if you have a 2 or 3 HP pump on an 1 1/2" piping system, you might have created pressures your system could not take. Or, your piping may have been damaged in storage or during installation if the weather was cold and the pipe were thrown around and developed invisible fractures. Did you use Schedule 40 piping?

Pam  Posted: 06/19/2017 11:27 AM 

I have a sand filter and pool was installed two years ago. I just turned on my pump and it blew a hole in the pvc pipe. Why would this happen?

Inyopools  Posted: 06/17/2017 12:38 PM  Inyo Product Specialist

martha - When you say 'cartridge", do you mean the whole grid assembly in your DE filter and that you replaced the grid assembly? If so, you may have too much DE powder in your filter that's blocking water flow. Try backwashing your filter again and then only adding 80% of the powder to recharge it.

martha  Posted: 06/15/2017 19:09 PM 

Have a hayward de filter that we just replaced the cartride since it was torn and now the pressure is building up after a few minutes and stopping the flow of water. The cartridge is not dirty and does not need to be backwashed...When we take the cartridge out and run it the pressure is fine...Any ideas?

Inyopools  Posted: 06/12/2017 13:49 PM  Inyo Product Specialist

Not pool happy - It sounds like you may have low water pressure and don't have enough pressure to supply all your jets. See our guide on "How to Correct Low Water Pressure in Your Pool System". Check for a clogged impeller first.

Not pool happy  Posted: 06/10/2017 23:44 PM 

OK, so I am searching for answers, and have not found any! last fall I blew out all my lines and no problems.I stated up my pool and my sand filter pressure is runing at aboutv 18 psi. My step returns are fine, but my two side jets are putting out almost nothing. I changed my filter's sand just now. No air leaks I can see. If I put a hose in one jet, water comes out the other jet when my step valve is off, with pump not running. Also if I plug one jet with the hose running in the other, and undo the disconnect just after the the filter, water comes out of it. How come I cant fnd the answer to my problem?

Inyopools  Posted: 06/09/2017 21:29 PM  Inyo Product Specialist

nonna - 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". Check first any connections before the pump that you may have disconnected when you changed the filter sand.

Inyopools  Posted: 06/08/2017 23:29 PM  Inyo Product Specialist

Jana - To my knowledge, there is no pipe installed in a pool system designed to pop apart when the pressure builds up. I would guess that whoever installed your system forgot to glue that connection.

nonna  Posted: 06/07/2017 10:45 AM 

we replaced our sand in the TR60 Triton, but the pressure rises from 10 to 20 within a couple of hours running the filter. Any suggestions on what may be the culprit? thanks!

Jana  Posted: 06/06/2017 21:37 PM 

I have a Hayward DE filtered around 20,000 gal pool. I am having a problem and lack the knowledge and need info. Is there a hard plumbed pipe that is supposed to be installed to prevent pressure valve from blowing. I have a pipe that keeps popping apart after filter runs for a little while. Thank you so much for any help.

Inyopools  Posted: 06/04/2017 22:03 PM  Inyo Product Specialist

Luis - First, you may have too much DE Powder in your filter. Backwash the filter again and then only recharge with 80% of the suggested load. Second, you may have backpressure building up in the top of your DE filter tank due to a suction air leak in the piping between your pump and the skimmer. A good indication of this is a strong blowback through the pump to the pool when you shut off the pump. If you filter has an air release tube down the center of the tank, make sure the tube and screen cap at the top are clear. To resolve your suction leak, see our guide on "How to Identify and Correct Air Leaks".

Inyopools  Posted: 06/04/2017 18:24 PM  Inyo Product Specialist

Andy - You may have backpressure building up in your filter tank. See Step 3, Suction Air Leak, and Step 4, Clogged Breather Tube, in this guide.

Luis  Posted: 06/03/2017 20:50 PM 

Have a pentair DE filter; I cleaned the filter completely psi 8-10; vacuum the pool but after a few hours the pressure went up to 25. I backwashed but again a couple hrs it went back up. Any suggestions on what could be the cause. I never had this problem before and have no clue what else to do.

Andy  Posted: 06/02/2017 6:01 AM 

I just purchased a Hayward Xstream. Runs great for a few hours but then pressure goes up. Removed cartridge, clean it and same thing. I can't get more than 2-3 hours before this keeps happening.

Inyopools  Posted: 05/30/2017 18:09 PM  Inyo Product Specialist

Dawn - If your system has high pressure, try opening up the relief valve at the top of your filter. If air comes out and your pressure drops, you have back pressure building up in the top of your filter tank. To correct his, see our guide on "How to Identify and Correct Air Leaks".

Inyopools  Posted: 05/30/2017 17:28 PM  Inyo Product Specialist

paul - 150 sq. ft. is the upper-end filter for a 1 HP pump and the lower end for a 1.5 HP pump. Most dealers suggest getting a filter that is 25% larger than what you need for a high water pressure buffer and for the convenience of not having to clean it as often. If I understand you correctly and you have bought three replacement filters in the last four years, it's a good indication that the filter is too small for the pump.

DE issues  Posted: 05/30/2017 9:33 AM 

I'm having an issue with DE streaming back into the pool only during vacuuming. On intial startup, I have no problems with the DE staying in the filter however 1 minute after starting to vacuum, it starts backstreaming. I checked the plates and the fingers and they all look fine. The filter is a HEYWARD EC50. Anyone else have this issue?