How to Reduce High Pressure in Your Pool System

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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

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Step 1

Why do I have high pressure? A pool system’s pressure is generally measured at the filter’s pressure gauge; the usual range is 10 - 25 pounds per square inch (PSI.) When you installed your filter, or after a thorough cleaning, make a note of the “clean filter” PSI. This rating will be used as a benchmark for pressure tests down the line.

High pressure is generated by three conditions:

The pump is pushing a higher water flowrate than the filter can handle efficiently. is trying to move a larger flow of water (GPM) than it can handle;
A blockage after the filter is causing a bottleneck, creating backpressure inside the filter. is a blockage (BLK) in the system after the pump - from the pump's discharge port.
A suction air leak before or at the pump is causing an air pocket inside the filter, which in turn creates the dreaded backpressure.
Excessive plumbing creates backpressure as the water’s momentum gets slowed by every turn or rise in elevation it makes.

Step 2

Clean your Filter. The most common cause of high pressure in a pool is a dirty filter. Take cartridges as an example, as the material sives dirt from your pool water, the cartridge fabric more and more clogged. The clogging means the water has fewer and smaller perforations in the filter media to squeeze through. This creates a traffic jam of water, that presents itself at spiking PSI reading on the pressure gauge. Cleaning methods for each filter type:

Cartridge - Spray down cartridge for standard cleaning. For extra dirty cartridges, we suggest using a liquid filter cleaner. Click Here to View the Liquid Filter Cleaner
DE - Backwash thoroughly, open filter to hose down grids and remove any linger DE powder and debris in base of filter. The Filter Clean chemical can also be used to fresh up old grids.
Sand - Backwash thoroughly. If the filter sand is older than 5 years or shows signs of clumping or channeling, replace sand.

Step 3

Check your filter media - If your filter’s pressure is spiking after changing your filter media you may have fallen into one of these traps:

Sand - too much sand slows filtration of the water through the tank, creating backpressure
Cartridge - Replaced your cartridge with the incorrect size. Though a cartridge may be the same overall dimensions as your original cartridge, the square footage may be significantly less. Less surface area, makes for less flow, then to high pressure. Click Here to View Replacement Filter Cartridges
DE - Installing the wrong grid size. Or applying too much DE powder when recharging the grids. Click Here to View Replacement DE Grids

Step 4

Clogged Breathing Tube - 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.

Click Here to View Replacement Filter Parts

Step 5

Oversized Pump - If your high-pressure reading has come directly after switching out your whole pool pump or pump impeller and motor assembly then you may have incorrectly sized the equipment. A pump’s flow rate is determined by its’ horsepower (HP,) whether it is a high or medium head style and the feet of head rating of PVC plumbing. If you jump up a HP, switch to a High head style from a medium head without accounting for feet of head differences then your pump’s flow rate could make a leap by 10 or more GPM.
If your filter was already maxing out on the smaller pump, all that extra water has nowhere to go, and the rise in backpressure begins.

Correcting an oversized pump:

Replace impeller with a lower HP version to lower the GPM output. This is by far the cheapest option, but make sure you refer to your pump’s schematics to determine if the diffuser needs replacing as well.
Replace whole pool pump with the correct match
If the new pump is a dual or variable speed, run only on the lower speeds.

Click Here to View Replacement Pump Parts

Click Here to View Replacement Pumps

Step 6

Closed Diverter Valves - If you have any diverter valves after the pump and filter, make sure they are completely open for max water flow. A partially closed diverter valve will throttle water flow, creating a flow bottleneck

Click Here to View Replacement Diverter Valves

Step 7

Enlarge Return Jets - 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.

Click Here to View Common Return Jets

Step 8

The key to eliminating high pressure in your pool filter system is reviewing potential flow restrictors or blockages in your system.

Clean Your Filter - 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.

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(1 to 40 of 177)

Pool pressure too high Posted: 9/20/2020

hayward filter cartridge was replaced, since then the pressure gauge remains at 33 when the pump is on. The only way to reduce it is to backwash for several minutes but within 5-10 minutes after turning on the pump the pressure goes up again to 33. With the old filter, the pressure was maintained at 20 and never had any problem. Not sure what else to do since this problem started with the new filter which was inserted on 08/2020
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InyoPools Product Specialist Matt S. Posted: 10/19/2020

What is the model number of your filter? Cartridge filters do not have a multiport valve, nor do they have a backwash function.
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Don Kelly Posted: 8/22/2020

Would a worn or leaking spider gasket in the sand filter head cause high pressure? I changed the sand less than a year ago and I'm running about 20 lbs pressure after a backwash.
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InyoPools Product Specialist Matt S. Posted: 8/24/2020

We're missing a couple of key facts: What is the standard "clean" psi when the new sand was put in, and at what PSI do you let it get to before you backwash? I don't believe a bad spider gasket could cause an issue with the pressure gauge. Are you sure the pressure gauge is working correctly? We also have this guide on lowering your pressure, give it a read:
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Paulina Wdowiak Posted: 6/1/2020

hi. I have a sand filter. Last year, before closing it work great. This year, we just opened the pool it reads 30psi. I backwashed and it didnt help. I changed the sand. Still 30psi. Any ideas?
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InyoPools Product Specialist Matt S. Posted: 10/23/2020

Did you check anything else on the system as we mentioned in the guide? Did you check for blockages in the pipe?
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Anonymous Posted: 4/16/2020

The cap on my pump keeps shooting off when I turn my pump on, even when I screw it back on tightly. What could be causing this?
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InyoPools Product Specialist Matt S. Posted: 4/17/2020

Is there a blockage in the return line or is the filter really dirty? The threads could be stripped, or there is a hairline crack that opens up when the pump builds up pressure.
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AMC Posted: 4/4/2020

When I backwash the psi drop down to 20psi but with in an hour it is back up to 30psi. It seems to stay there but I don’t like it that high. I have just replaced the DE filter, the backwash device was replaced last year. Strangely after the backwash device was replaced, I seem to get air in the motor filter and the only why to fill with no air was to backwash. It would fill with no air the run fine. Pool service crew told me it was fine. The pool struggled to stay clear so this year I replaced the DE filter but things are not going well. If you can share an advise that be awesome.
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InyoPools Product Specialist Matt S. Posted: 4/7/2020

If your pool is not clear, either from debris or algae, then that would explain the spike in pressure soon after backwashing. You may be overdosing the grids with too much DE: How Much DE to Add?
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Tim Llorens Posted: 3/22/2020

Will cracked cartridges cause high psi
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InyoPools Product Specialist Matt S. Posted: 3/23/2020

I guess it would depend on how bad they are cracked. Are they cracked enough to hinder flow rate through a portion of the pleats? If so, then yes, it would cause high flow rate. But Chances are if a cartridge is causing issues, either it is dirty and needs cleaning or replacing, or it is too small.
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Flavio Posted: 12/4/2019

I have a question: To backwash my filter what must to do with the water pipes, do I need to close any valves or they must be remain opened as in the filter position? Thanks
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InyoPools Product Specialist Robert M. Posted: 12/4/2019

Hello Flavio - You shouldn't have to change any other valves besides the filter valve. The valve will reverse the flow of water through the tank and flush it out of the waste line.
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Amran Anas Posted: 11/17/2019

Hi there. I got my cartridge filter. But after 2 hours i turn on pump my psi went really high. And i have to wash the filter everyday. My filter just 2 months old
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InyoPools Product Specialist Matt S. Posted: 11/19/2019

Have you completed any of the troubleshooting mentioned in this guide? If not, then I would begin with that.
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Weston Posted: 8/6/2019

I have indoor inground pool with a sand filter. Last week the filter was at 30 psi. Backwashed it and went back to normal OP 10 psi. Now pressure is back to 30 psi
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InyoPools Product Specialist Matt S. Posted: 8/7/2019

Try backwashing it again; if the filter's pressure rises quickly again, you may try a filter cleaning cycle. If your filter sand is more than a few years old, then it may be time to replace the sand.
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Brandon Posted: 7/29/2019

Hello, I noticed my pressure gauge reading 50-60 PSI. The needle does not drop significantly when the pump is turned off. There are cracks in the valve casing with water leaking out. PSI does not change after backwashing and I do not have cloudy water problems. Pump is pentair superflow 1.5 hp. Filter is Hayward S244T. PVC is 1 1/2 inch. Return orifices are 1, 1 inch hole, and 3, 1/2 inch holes. Could my high pressure be due to the three 1/2 inch return orifices? Or an air leak? I am planning on purchasing and replacing the entire valve casing because it is leaking, but I need to fix it high pressure problem too. Thank you
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Bobby Posted: 8/29/2019

Brandon, I'm having the exact problem. What exactly was the cause of the issue in your situation? I'd really appreciate any feedback. Thanks
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InyoPools Product Specialist Matt S. Posted: 7/29/2019

Have you considered that the pressure gauge might be broken? It is a pretty cheap fix, I would try a new pressure gauge.
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John Posted: 6/18/2019

We just moved into a house where the Hayward catridge pool filter pressure was 28psi. I cleaned the filter and it went down to 20psi. When I took the catridge out to clean it the filter had no air relief tube in it. Would this cause the pressure to be high?
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InyoPools Product Specialist Matt S. Posted: 6/20/2019

Going by your description, it sounds like the pressure was high because the cartridge was dirty. The pressure going down after cleaning the cartridge, seems like a normal thing.
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David Mailley Posted: 6/17/2019

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

How to Identify and Correct Air Leaks
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Scott H Posted: 6/17/2019

Would an old Jandy DEL 60 filter cartridge cause pressure to rise? I’m backwashing 3-4 times a day and noticing the water is slowly becoming cloudy and doesn’t seem to be filtering properly. We just replaced the pump. I’m embarrassed to say the DE grid is the original (around 13 years old). I’m about to order a complete replacement as a DIY project, but want to see if there are other possible causes.
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InyoPools Product Specialist Matt S. Posted: 7/10/2019

Is it cloudy because you used an algaecide, and you need to backwash to clear excess algae waste? Or is this cloudiness caused by particulates in the pool, that are clogging the pool? Before replacing the grids, you can try giving them a chemical soak. That may refresh them enough to prevent excess backwashing.
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Scrogg 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 Matt S. Posted: 6/14/2019

It would not.
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David Schwartz 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 Matt S. Posted: 6/6/2019

It releases air that is trapped in the tank of the filter.
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Bobbie 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 Matt S. 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?
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Keith 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 Matt S. 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.
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Keith R Corbett Posted: 5/20/2019

Then why is it i can take filters out and it runs fine
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InyoPools Product Specialist Matt S. 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.
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Keith R Corbett Posted: 5/20/2019

Like to but broke
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Tammey 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 Robert M. 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.
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