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 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: 
  1. 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; 
  2. 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. 
  3. A suction air leak before or at the pump is causing an air pocket inside the filter, which in turn creates the dreaded backpressure.
  4. 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 exmaple, as the material sives dirt from your pool water, the cartridge fabric more and more clogged. The clogging means the 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 Filter Clean.
  • 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.
  • DE - Installing the wrong grid size. Or applying too much DE powder when recharging the 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.

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.

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

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.

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.

Comments

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(1 to 40 of 161)

 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
 Reply

InyoPools Product Specialist  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.
 Reply

 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
 Reply

 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
 Reply

InyoPools Product Specialist  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.
 Reply

 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?
 Reply

InyoPools Product Specialist  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.
 Reply

 Posted: 6/17/2019 

How would I track down a suction leak. My issue sounds exactly like this could be happening
 Reply

InyoPools Product Specialist  Posted: 6/19/2019 

How to Identify and Correct Air Leaks
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 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.
 Reply

InyoPools Product Specialist  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.
 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 

It would not.
 Reply

 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!!
 Reply

InyoPools Product Specialist  Posted: 6/6/2019 

It releases air that is trapped in the tank of the filter.
 Reply

 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
 Reply

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
 Reply

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
 Reply

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.
 Reply

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.
 Reply

 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.
 Reply

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?
 Reply

 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.
 Reply

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?
 Reply

 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.
 Reply

 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.
 Reply

 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