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How to Reduce High Pressure in Your Pool System

WRITTEN BY: Inyo Pools

3.12 out of 5 stars on 56 ratings
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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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(161 to 194 of 194)

mf2593 Posted: 5/29/2016

My husband always took care of the pool but unfortunately he is gone and I am clueless but have been reading and reading and still have not fuigured it out. I have a DE filter system, 24 ft above ground pool and I just replaced the Hayward pump because I thought that was the issue. The pressure is reading over 20 constantly and after 20 minutes there is no intake or output of water. I have cleaned the fingers to the filter over night in muriatic acid, I am turning the pump off every 20 minutes and "bumping" then restarting. I am literally at the point of just getting rid of the pool. Any suggestions or advice would be GREATLY appreciated.
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rogos Posted: 5/27/2016

Have a Kayak 12 X 20 4' pool with a Sta-Rite PLM100 filter and a hayward 1.5 hp pump, just put a new filter cartridge in for 3 days and eventually the top of the filter popped and water started spraying out from middle of the filter, where top meets bottom. This has happened quite a few times this year with my other cartridges, but I was shocked it happened with the new one. I felt the new cartridge would solve my problem, but it didn't. Any idea why this is happening. Pressure is usually 15 to 20.
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vic Posted: 5/26/2016

I have a problem with pressure build up, the prime seems somewhat normal everything works fine for about 5 hours then the pressure builds to 25 and suction in the skimmers stop which halts water discharge into the pool. after i bachwash the pool i can get the pressure to 15 and it runs again. i have cleaned the filter, checked for leaks found none. the pool is a 20x40 40,000 gallon pool salt water with a de filter.
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Mo Posted: 5/25/2016

I have a hayward DE4820 filter and I change the water pump to a hayward super II pump 1.5 hp... the the length of my personal
Return pipe is 5-6 feet away from the pool....my psi is one. The 30.... a few solutions suggested are to change the i.peler or to add more pipe to the return so it can decrease pressure... is this something it will work or should I just change the impeller in the water pump? Thanks for the videos by the way ... they help a lot .
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InyoPools Product Specialist Dennis R. Posted: 1/12/2016

ozstar - Unfortunately we do not handle this product and I am unclear what you refer to as a blank plug. Generally when a "clean" cartridge is showing a 100 psi reading, it's because the cartridge isn't really clean. Over time oils and chemicals build up in the folds of the cartridge that are hard to get out. This clogs what appears to be a clean cartridge. Have you tried replacing the cartridge with a new one?
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ozstar Posted: 1/10/2016

I have had an about 12 rectangle above ground pool for 20 odd years. For the last 3 I have a Pantera PCF60 cartridge filter and Onga LTP550 75hp pump and all has been fine.

Recently the blank plug in the filter came out under pressure and it does with or without the cart in.

Without the cart in the filter, the water really came out of the outlet into the pool at a massive rate then after 20 secs or so, the blank came out.

Even after a good cart clean and brush with detergent the gauge start at near 100.

Water is clear and no blockages in expandable plastic piping.

Any ideas please?

Thanks
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InyoPools Product Specialist Dennis R. Posted: 11/19/2015

50-100 psi - Your water pressure reading if accurate is dangerously high to the point where something could blow. I would replace your pressure gauge first. It sounds like it may be damaged. If you have good flow into your pool returns, your problem could be a blockage in your spa input pipes. Check that your spa diverter valve is open then check for a block in the spa input piping. If you have minimal flow in both your spa and your pool check your filter. If you have a cartridge filter, see if you have flow with the filter out. If that works, buy a new cartridge filter. If you have sand, backwash the filter 3 times to get all the debris out of the sand.
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Anonymous Posted: 11/18/2015

just started cleaning the pool and the pressure is between 50-100 psi and cant really read the accurate reading due to their water inside the meter. the spa normally have water coming in and into the pool but yesterday it stop and there no water coming into the spa im a bit confused if its blockage due to the dead algae or something?
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InyoPools Product Specialist Dennis R. Posted: 8/18/2015

high spa pressure - If your system had been working in either spa or pool mode, I would guess that you may have developed a blockage somewhere in your spa lines. You may have to have a professional come in to check your lines or you can try blowing them out yourself with a Drain King or a wet vac. There are several blogs on the internet on this subject.
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Anonymous Posted: 8/17/2015

I'm having a problem with my pool pump pressure. When in "pool mode" the pressure is around 10#, but when i switch to "spa mode" the pressure spikes to over 20#. This has caused my system to develop leaks, and has never been a problem before. Any suggestions? If I had done something different when cleaning the filters wouldn't the pressure be high all the time?
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InyoPools Product Specialist Dennis R. Posted: 7/25/2015

diveit - I don't know what the size of your pool is, but, generally speaking, a 1 HP pump is what is used on a medium size pool, 8,000 gallons to 15,000 gallons. If you have a suction cleaner, you might also need a 1 HP for more effective cleaning. I would tend to suggest getting a larger filter and keeping the current converted pump.
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diveit Posted: 7/24/2015

Sorry for yet another post, but this might be good data for many others would have high pressure...
I changed the impeller and removed our restrictive Hayward chlorinator (do not use it). Result is a pressure down but still at 21-23psi. My elderly System 3 filter has now developed a leak with all these pressure changes. Should I change to a larger System 3 filter, or just buy the same (would be nice to have my current new filters fit the new System 3). If I buy the same, I assume I would change to a smaller pump? Thanks again for valuable advice.
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InyoPools Product Specialist Dennis R. Posted: 7/22/2015

diveit - You have the correct impeller numbers for your uprated motor. And I would try the impeller replacement first before looking at a smaller motor. It should work.
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diveit Posted: 7/21/2015

This info is about what I expected. So, will going from the current impeller, C105-238PB at 4.75", down to C105-238P at 4.685" will do the trick? Do I need to reduce the motor to 3/4 hp? Thanks
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InyoPools Product Specialist Dennis R. Posted: 7/21/2015

diveit - By going to a 2" system with flow friendly fittings, you may have reduced the flow friction (head) to the point where the water flow is overpowering your existing filter. And this may have been further aggravated by installing a larger pump. Your Sta-Rite S7M120 filter is designed to handle 50 - 80 GPM. With low head, your new pump can generate over 100 GPM. If this is your problem, it can be corrected by buying a larger filter or by downgrading your pump by replacing its impeller with a size smaller. See our guide on "How To Downsize a Pool Pump Impeller".
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diveit Posted: 7/20/2015

I recently purchased a large Hayward HP21404T heat pump from you folks. When installing, I decided to change out the 1.5" crazy (tons of 90deg fittings) plumbing for 2" throughout with flow friendly fittings (sweep 90s, etc.) The pressure in my system jumped from 16-20 psi to 26-30psi. I am also noticing that the motor I have is not the original 1HP, but is 1.5HP. Is my pump too large?
System is:
Filter - Stay-Rite S7M120
Pump - DURA-GLAS II P4R6E-151L but with A.O. Smith USQ1152 1-1/2 HP Up-Rated Pool Motor
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InyoPools Product Specialist Dennis R. Posted: 6/28/2015

high pressure - All I can say at this point is to recheck anything you changed in the new installation. Check for blockages after the filter. Try opening up any return diverter valves. Then you might call your pump/filter manufacture to see if they have any other suggestions.
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Anonymous Posted: 6/28/2015

Thanks for getting back to me. I tried sealing all of the suction side connections but it did not lower the pressure. Any other thoughts?
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InyoPools Product Specialist Dennis R. Posted: 6/27/2015

high pressure - Small suctions air leaks are sometimes difficult to detect. Try temporarily packing plumber's putty around each of the suction side connections. If this corrects your high pressure problem, you know the leak is in one of these connections. Take them off one at a time over 1-2 days to isolate the leak.
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Anonymous Posted: 6/27/2015

I had to replace my filter and cartridge at the same time this year. Ever since I changed them, the pressure has been very high. It starts at about 22 psi after I clean the filter and within the course of a day or 2, its up to almost 35 psi. I take the cartridge out and hose it off even though it is not very dirty and the pressure goes back to 22 psi and the cycle repeats wihtin a couple days. I dont remember what the psi was before the pump and cartridge replacement but I know it was significantly lower. Previously, I would need to wash the cartridge about once a month after the pressure went up 10psi. This is a 30000 gallon in ground pool with 2 skimmers and a bottom intake. There is no air or leaks in the system. I check all of the things you mentioned in this exchange. The new hayward pump is an exact match with the old 1 and so is the cartridge. Cant figure out what is causing this. Any ideas?
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InyoPools Product Specialist Dennis R. Posted: 5/23/2015

high pressure - If your pool's pressure was good until recently, check the following. If you recently had a lot of algae or debris in your pool that you cycled through the filter, the filter may be severely clogged and you may have to clear it by cycling through a backwash/rinse cycle three of four times. If you have a sand filter and haven't change the sand in 5-7 years, it's time to change the sand. Also you may have a defective gauge that should be changed.
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Anonymous Posted: 5/20/2015

The pressure on my pump is in the yellow. How do I reduce this pressure? I called the local pool store where it was purchased and they said it needed to be backwashed. I did this and the guage has not changed. Please help!
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InyoPools Product Specialist Dennis R. Posted: 4/18/2015

bcomments - I would guess that your pump was too large for your filter. Check the GPM rating on you pump to the GPM rating on your filter. We usually recommend buying a filter that is one size larger than required to avoid this issue. Also reduces number of backwashes.
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bcomments Posted: 4/15/2015

what could cause your sand filter tank to just split open
and water come jetting out? 4 years old
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InyoPools Product Specialist Dennis R. Posted: 2/25/2015

Sue - These two floor pool configurations are something we don't normally get into. You might call a pool equipment manufacturer like Hayward to see what they think. Their number is 866-772-2100.
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Sue Posted: 2/24/2015

Can anyone advise? Have built a pool on the first floor with the pump in a room below on the ground floor. The filter seems to operate under too much pressure. The sandfilter split and a bigger one has been put in. After that it leaked slightly from the lid where the waste basket sits. Now it is leaking from where a pipe just behind this basket. What can be done to reduce the pressure that is created from the filter being so much lower than the pool?
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InyoPools Product Specialist Dennis R. Posted: 12/30/2014

DIYcheapskate - Your Pentair FNS60 DE Filter is one of the largest on the market and can handle up to 120 GPM. 120 GPM is on the upper operating range of a 2 HP full rated Pentair WhisperFlo Pump depending on the resistance in your pipe system. Typical operating rage for a 2 HP pump is 60 to 110 GPM. Your pump and filter is a good match.
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DIYcheapskate Posted: 12/27/2014

I have a pentair fns60 de filter and a whisperflo 2hp pump. Is my pump to big for filter system? Where can I look to figure out what pump HP should be paired with sized filter. Any help would be great. Thanks
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InyoPools Product Specialist Dennis R. Posted: 6/26/2014

breather tube - If there is a screen on the top end of the tube, take that off, clean the end of the tube, and blow it out with your mouth.
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Anonymous Posted: 6/26/2014

What is the best way to clean out breather tube?
Thanks!
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InyoPools Product Specialist Dennis R. Posted: 6/24/2014

new_pool_owner - I would have concluded that your pump was too large for your filter and system in general, but if your system was operating at 10 psi before you had closed off the valves, the size of the pump should not be an issue. If you've check everything else in this guide, I am at a loss on how to correct your problem. I would suggest calling Hayward at 866-772-2100. Their tech staff should have some suggestions.
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new_pool_owner Posted: 6/23/2014

We have a sand filter, with a hawward multi-port valve. After emptying the pre-pump filter basket, we closed the valves that lead to the pump and the pool. The pool is on higher ground than the actual pump, so this causes more pressure to begin with. After cleaning out the basket, and replacing the lid; the pump was turned back on to 'filter' and the pressure was high. We quickly turned off the pump because we realized the valves were still closed. With the pump off, the pressure is still too high. We set the filter to backwash, and then rinse, then back to filter. The pressure is still high. If the valve for incoming (into the filter) pipe, about half way-- then the pressure goes back down to about 10. But if it's wide open, then it's high at 20. We fear that we've broken something! Help!
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InyoPools Product Specialist Dennis R. Posted: 4/29/2014

Luis - If your filter pressure is going from 10 to 35 in 30 minutes, I would say that the algae is clogging it up. Try reducing the algae with an algaecide. See our guide on "How to Clean a Green Swimming Pool (Algae)".
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Luis Posted: 4/28/2014

Hi, I'm very frustrated to the point that I have been thinking about selling my house. Last year we changed the de filter including the multiport valve. Something wasn't running right. The pump wasn't priming. We had to replace it the motor. Since last summer the water hasn't been clean. Now de filter pressure goes very high. Without any de the pressure is about 8 With the de is about 10 The bad thing is that after 30 mins the pressure goes up to35. Could it be the algae?
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