High pressure in swimming pools is something we hear about quite frequently. We get tons of phone calls, emails, chats, and even questions on our new INYO Pool Forum specifically on how to reduce high pressure in your pool system. There are several high-pressure scenarios that can arise on any day for a number of reasons. Each pool setup is different and therefore variables play a role in determining the root cause. Still, reducing high pressure is a common occurrence that can frequently happen if you’re not careful. In this blog post, we address what high pressure means to your system, the different ways in which pressure can build, and ultimately how to reduce the high pressure in your pool system. Hopefully, our blog is your one-stop-shop for all of your issues related to high pressure.
What Is High Pressure?
When pool owners claim they have high pressure in their pool systems, what exactly do they mean?
For the most part, pool filters are very straightforward products. Dirty water goes in one way and clean water comes out the other. One thing that is necessary for proper filter operation is pressure. Pressure drives the water to flow throughout the filter. Having too little or too much pressure makes it difficult for the filter to function properly. That is why it is important to keep a close eye on your pressure levels. The most important tool pool owners have at their disposal to monitor their pressure levels is the filter’s pressure gauge. Pressure gauges are dials that indicate how the pressure is holding, or not holding, in your pool. So, what exactly is normal pressure?
It is extremely difficult to give an exact “normal” pressure reading that satisfies every pool. That is because every pool is unique to its design and setup. Well, if that’s the case, how do we know what “normal” is? To be honest, that number is quite relative. Ideally, the “normal pressure” for any pool is the number on your pressure gauge when you first installed your pool filter and everything in your pool is running smoothly. However, this is impossible for most pool owners as they usually inherit the equipment with the pool. If you do not have records of this number, your next best result is the number on the pressure gauge directly after you have cleaned, or backwashed, your filter. For the most part, 8-15 psi is considered “good”.
It’s a good idea to write this number down once you have identified what the “normal” pressure is for your filter. This is the number you will reference to determine if your pressure is high or low.
Why Is My Pressure High?
After you have identified your “high pressure” number, focus your attention on the how’s and the why’s. It’s one thing to fix an issue, but it’s another to identify the root cause to the issue and to prevent it from happening again. Trust us, the latter benefits you the most in the long run. There are a few different areas around your pool that can lead to an increase in pressure. This blog post guides pool owners in determining which area is causing the pressure build up, how to reduce the pressure, and how to prevent it for the future.
Pressure builds under these three conditions in your pool system:
- Your system is trying to move a larger flow of water (GPM) than it can handle
- There is a blockage in your system AFTER the pump, usually from the pump’s discharge
- There is a suction air leak BEFORE or AT the pump that causes air to build up in the top of the filter
So what happens if you go to check your pool’s pressure gauge and the pressure reads much higher than normal?
Dirty Filters
A pressure gauge reading of 5-10 psi above your recorded normal pressure is an indication that your filter is dirty and needs cleaning. A higher pressure reading on your gauge means your filter system isn’t allowing water to flow through fast enough. A dirty or clogged filter is probably the most common problem that ultimately leads to high pressure. Don’t forget, a top priority for pool owners is to ensure that their filters are continually cleaning and filtering the 
water. No one wants to swim in a dirty pool, right? Over time, fine debris, oils, and chemicals embed itself in the creases of the pleats in the cartridge. Unfortunately, the embedded material won’t come out with a simple spray of the water hose. As a result, clogged filters increase the pressure in your system and leave your pool water less than ideal.
To help get rid of all of the gunk left in the cartridge, we recommend using a cartridge cleaner. Cartridge cleaners remove oils, grease, and other debris that clog filters that regular water cannot remove. Regular use of filter cleaners increases your filter’s lifespan and efficiency, however, they do not preserve your filters forever. At some point, they will get so dirty that the only solution is to replace them.
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Suction Air Leak
An air leak is the second most common reason for an increase in pressure and back pressure. Air leaks only occur on the suction side of your system. A suction air leak is like trying to use a straw with a tiny hole in it. Typically, if you have a large suction leak, the pump loses prime before the pressure even builds up. But if you have a small suction leak, air sucks into the system and eventually builds up in the top of the filter tank. Over time, the back pressure builds up to the point that it significantly reduces water flow 
through the filter and out to the pool. Once the pump is off, the pressure surges back through the pump and skimmer.
Bubbles and splashing in the pump basket are early signs that you might have a suction air leak. This indicates your pump is not getting the required amount of water it needs to function properly. Instead, air is getting into the system and semi-starving your pump. Another indication you have an air leak is bubbles coming back into the pool from the returns. If you notice these things, we recommend you take immediate action. Your job- locate and stop the source where the air is getting in.
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Clogged Breather Tube
The majority of pool filters contain a breather tube. A breather tube automatically purges air trapped at the top of the filter. Typically, the tube runs from just under the dome 
to the bottom of the tank. Some of the D.E. filters, though, have built-in breather tubes that integrate into the top manifold assembly and exit through the discharge line. And some filters do not have breather tubes at all. If the breather tube becomes clogged or damaged, air pressure at the top of the filter tank builds up.
Although a small piece of equipment, the filter’s breather tube plays an important role in ensuring your filter system’s pressure remains stable. Don’t forget to check for small cracks or damaged pieces along the tube. If you are in need of a replacement breather tube, use your filter’s make and model to cross- reference the correct replacement. Or, you can give us a call and we’d be more than happy to help.
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Oversized Pump
A pump that is oversized will do more harm than good for your swimming pool system. Ideally, your pump should push enough GPM’s to push all of the water through your plumbing and filter and back into the pool within an eight to ten-hour time frame. If for whatever reason you miscalculated your feet of head or the previous owner oversized the pump, you just may have a larger pump than your system can handle. As a result, your system’s pressure goes up.
This is also a common problem when pool owners replace their motor and disregard the horsepower (HP) and Service Factor (SF) relationship. Replacing a 1.0 HP motor with a 1.5HP motor runs the risk of your pump is too large for your pipes and your filter. If the pipes and filter cannot handle the greater water flow, pressure builds up after the pump. When the pump shuts off, the pressure surges back through the pump, the suction pipes, and back into the pool.
Before upgrading your pump size, make sure you check your filter’s turnover rate and GPMs to ensure a proper fit. The part number and model number for the exact replacement motor is on the motor label itself. We always recommend using the information on your existing motor in order to find the correct replacement.
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Closed Valves
A swimming pool diverter valve controls or diverts, the flow of water from one part of your swimming pool system to the other. If you have a diverter valve after the pump, you might have inadvertently closed off a section of your return lines. If this is the case, you are restricting the total return flow and causing back pressure in your system. This is an easy fix. You can relieve the pressure by opening up the return lines.
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Undersized Return Jets
Although most pool owners won’t link high pressure with an undersized return jet, it definitely can be the case. An undersized return jet prevents the natural flow of water and creates back pressure. Plugs left in your pool wall or restrictive eyeball fittings can also increase back pressure.
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Check Your Gauge
Last but not least, check your pressure gauge. All of this talk about checking different areas around your pool, when in fact, it can easily be the pressure gauge. Pressure gauges do not last forever and are fairly simple to replace. If you’ve had your gauge for a few years, or the gauge is damaged or cracked, replace it. You don’t want to waste time and money on ensuring you really do have a pressure problem when you can easily just change the gauge.
No Pressure…
Succumbing to pressure, whether in your personal life or in your pool system, is never a good idea. Unfortunately, in order for a swimming pool system to function properly, a certain amount of pressure is necessary. So. you can’t get rid of pressure altogether. What you can do is manage your pressure levels. Once you understand what causes your pressure to rise, the better you can manage them.
And when in doubt, check out our video on How To Reduce High Pressure in Your Pool System
Hello, I have a Hayward DE4820. It used to run between 5 and 12 PSI. Now it runs 20+. I backwash it and it will only drop down to 10 PSI, then in a hour or two it is back up to 20+. I have double checked for air leaks, replaced the breather tube on the manifold. Cleaned my filters multiple times. Does not make a difference what position I have the valve on. I am at a loss. Any advice would be appreciated. Thank you
The filter may require a deep clean; this means backwashing, removing the grids, and giving them a chemical soak. Backwashing does not remove all the DE powder within the filter, so while the grids are soaking, I’d all scoop and remove any leftover debris left in the bottom of the tank.
Hi,
My sand filter pressure keeps rising slowly – going up 2-6 psi in 24 hours and I can’t figure it out! I replaced the sand, inspected the laterals, and backwashed multiple times. My water looks good and I ran it on recirculate for 24 hours with no rise in pressure, so pipes should be clear. I don’t seem to have a leak. What should I try next? Everything seems normal except the pressure rise.
Thank you!
First, I would confirm that you put in the correct amount of sand. If you put in more sand, the water will not move as efficiently as it should. If you are opening the pool, there may be some remnants of the months of inactivity. I suggest using a flocculant just to clear everything in one fell swoop. If flocculant does not clear up the problem, I would recheck the water chemistry levels.
I have a High Pressure reading accompanied by a loud noise coming from the filter canister…not the pump. What can be causing this loud “squeal”?
That is hard to say because those two symptoms are contradictory. Usually, if there is a hissing or squeal noise sourcing from the filter, the issue is an air leak. But if there is an air leak, the pressure in the filter will dip, not rise. Can you pinpoint where the squeal is coming from in on the tank? Also, what type of filter is it, sand, DE, or cartridge?
There may be a blockage causing a restriction in low, which would spike the pressure and maybe create a noise.
My gauge is not moving what’s wrong?
My gauge is not moving while I vacumm is this normal? I am new at this
Just moved to a new house and my Hayward Cartridge filter(12002) is missing the air relief tube for some reason. Pressure was at 30psi until I cleaned the filter. It is now down to 20psi. Can I assume that a new relief tube would reduce the air pressue even more?
I’ve always had bubbles on the intake side but never had a back pressure problem (the pool is nine years old). Last year I replaced the guts of my diverter valve in an attempt to stop the bubbles but it didn’t make any difference. I’ve wrapped plastic wrap around the connections of the suction side but haven’t found any evidence of a vacuum leak. I have not dug underground yet. Previously high pressure was always around 20 psi. After backwash it would go down to 12-15 psi. Now it never drops below 19 psi after I backwash and hasn’t gone above 21 psi but I get a huge WOOOSH after the pump turns off after running for 8 hours and it blows all the water back through the intake side to the point the skimmer basket is blown upside down. It takes more than 1-1/2 hours to build up enough air to do this as I’ve turned the pump off after that amount of time (1 1/2 hours) and I don’t get the back pressure. I replaced the sand in the filter last year. At the beginning of this season my pump shaft seal went. I assume because this happened and the pump ran too dry. My gut feeling is there is an obstruction on the pressure side but I don’t know if this could be the case (maybe something I did wrong replacing the filter sand). Is there a setting I could try (like “recirculate”) to see if bypassing the filter might narrow down the problem? Thanks
Heya – did you ever resolve your problem? I am encountering pretty much identical symptoms. I’ve just finished replacing the shaft seal to try to resolve, but hasn’t changed anything that I can really tell.
Thank you so much for all the information here. One question I have, in reading info here it seems that my particular filter and cartridge may be too small. I have a 100 cartridge but should have a 150. Could that cause too high pressure in my system? Thanks
Yes, it can.
I am struggling to properly troubleshoot the high pressure readings on my pool pump system. I have an older style Pentair Challenger pump system with a 2 year old 2HP motor & DE Filtration. So, I have had three system failures in the last 2 weeks: High pressure reading and then noise in the pump. I disassembled the motor from the pump housing and discovered my difuser was broke off at the neck. I replaced the unit and reassembled the pump and motor. After turning the pump back on the and priming…the pressure skyrocketed to 30+ and seal plate broke off and the motor came completely off the mount and ring clamp assembly. I bought the new part with associated seal spring and reassembled. It worked for about a week and then back to high pressure and now a broken impeller. The impeller broke apart at the neck. I don’t get it…what am I missing?
The high pressure could be caused by broken pieces of the pump clogging up the pumping system.
To focus on why the pump parts might be failing so rapidly: Do you use chlorine tablets? If so, do you use a traditional chlorinator or do you drop them in the skimmer or pump basket?
If the pressure gage is broken will your pump work harder because of it? Mine is for sure broke it reads 20 when the pumps off but, you can tell the pump is working harder because where the jet is it’s making funny sounds. Didn’t have this problem last year but didn’t know if the gage could be the only problem?
The pressure does not affect the pressure, it just provides a reading of the pressure in the tank. Your pump is probably struggling because you haven’t cleaned your filter in a while. Simple solutions to this: buy a new pressure gauge, clean your filter.
I have the same issues has a person above with the pool pressure going up after an hr or two. I have however had my cleaned at the pool store and then tried brand new grids. The only thing I changed was I had two 90 degree fittings to clean up my lines going into the house, I would think if that was the issue it would have high pressure right off the bat. When I open my filter the upper manifold is covered in DE powder, I don’t have powder coming back into the pool but could the manifold be cracked and I don’t see it?
Hi. We recently purchased a home that came with a pool. Ever since opening the pool, the filter has been running high – over 40! The old owner had the pool open last summer, so I know the filter wasn’t just sitting. We checked to make sure everything was opened and we don’t see an obvious leak. What would make it run that high?
Hi all,
Appreciate any suggestions anyone can provide. I have a DE filter system. My system pressure constantly goes up to 20+ after the pump is running for 2+ hours. I notice that when I do backwash, the pressure goes back to normal reading of around 10. Until it builds up again to 20+ after a couple of hours. I also notice that when I put the setting to recirculate, some water goes out to waste. Appreciate any advise to resolve this issue.
When was the last time you gave your DE grids a chemical soak? The soak should clear any dirt from the grid fabric that backwashing can’t. The soak should free up grids space for freer flow.
The water flowing from the recirculate port is a valve issue, different from low pressure. Read this: Why Is My Multiport Valve Leaking?
Thanks for the reply Matthew! What exactly is chemical soak? I actually took out the DE filter multiple times to rinse it with hose. Wouldn’t that have removed and cleaned the fabric?
Thanks again!
Have a look at this guide: How To Chemically Clean a Pool Cartridge Filter
For singe reason my Dolphin automatic pool cleaner climbs out of my pool and loses it’s prime. When I took the cleaner out my skimmer now makes a slurping sound and my skimmer doesn’t seem to take debris of of the surface. My cartridges have just been replaced. What can I do to get my Dolphin and skimmer working again?
Can you give me the full make and model information for your cleaner? I need to know what you are working with. Because the only Dolphin cleaners I know of, are made by Maytrnoics and they are robotic cleaners that do not require any hook up to your skimmer.
Also, how long did the main pool pump run dry? If it ran dry for longer than 20 minutes there is a chance some of the internal parts are damaged/melted. Do you see any leaking water coming from the pump? Or is the equipment pad wet?
Excellent article. I learned a lot from reading this. I take care of my own pool and am intimidated at times. This helps me immensely