How to Correct Low Water Pressure in Your Pool System

WRITTEN BY:  Inyo Pools

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Have you noticed a significant decrease in your pool line pressure either building up or overnight? It was 15 psi and now it's 6, your water isn't flowing as fast and your pool cleaner has stopped or is running much slower. This guide addresses some of the common causes of low pool pressure. They are presented in the order of simplest to fix to more difficult.


Step by Step


Step 1

First a short discussion on how a pool system works. The piping in a pool has two sides: the suction side that is before the pump and a pressure side that is after the pump. The pump creates a vacuum that sucks water from the pool and then pushes it back into the pool through a filter. A leak in the suction side will cause air to be sucked into the system. A leak on the pressure side will cause water to spray. If you have a blockage in the suction side of the pump, the blockage will restrict the amount of water to the pump that will result in low pressure. A blockage in the pressure side, like a dirty filter, will have the opposite effect and will cause the pressure to go up. Here are the common causes for low pressure - the easiest to fix is explained first.

Step 2

CLOGGED SKIMMER BASKET - If your skimmer basket is full of debris, you are effectively shutting off the pipe between the skimmer and the pump. Generally this will reduce the flow of water to the pump. If the pump has less water entering it, it is moving less water out. This means the pump is doing less work that in turn will reduce water pressure.

Solution: Clean your skimmer basket by removing any debris.

Step 3

CLOGGED STRAINER BASKET - It is the same story as above. A clogged strainer basket means less water flow that leads to less water pressure out the returns.   

Solution: Clean your strainer basket by removing any debris.

Step 4

CLOGGED FILTER - Again, if water can't get through a clogged filter, you will have less water flowing out of the filter. Incidentally, this will increase the water pressure in the filter signaling that it is time to clean the filter.  

Solution: Wash your cartridge filter. Periodically soak the filter overnight in a TSP solution to get the grease and gunk out of the folds. Grease is produced by suntan lotion, sebum (oils secreted by the human body) and pine tree needles. Then soak the cartridge in a weak solution of muriatic acid (10:1) to get the minerals out of the folds. Use the TSP before the acid or the gunk will set up in the folds. For sand filters you will need to backwash as required. Change the sand every five to seven years. In between changes, if sand has caked on top, take one to two inches off at the top and replace it with new sand.

Step 5

TOO MANY FEATURES OPENED - The pump is only designed to move so many GPM. Too many water features are like too many hoses on a sprinkler system. The first one has great pressure. Subsequent hoses will reduce the water pressure.

Solution: Alternate which features are turned on or replace the motor in your pump with a larger one. Make sure your existing filter will support the larger pump. You may also have to replace it.

Step 6

CLOGGED IMPELLER - This problem is often overlooked. If the impeller becomes clogged with debris, water can't rotate out the sides of the impeller. This decreases suction which reduces water flow through the pump.  

Solution: Clean out the impeller. See our guide on "How To Clean Out a Pool Pump Impeller".

Step 7

SUCTION LEAK - A suction leak in the suction side of the pump can cause a number of problems. If it's large enough, too much air will be sucked into the system, and the pump will lose prime. If it's smaller, air will be sucked in through the pump and start to collect at the top of the filter tank. After some time (sometimes a few hours) air pressure at the top of the tank will create enough back pressure to reduce the flow of water significantly. When the pump is shut off, this back pressure will cause the water in the suction pipe to surge back and sometimes create a column of water up though the skimmer.  

Solution: Find the suction leak and close it. See our guide on "How to Identify and Correct Air Leaks".

Step 8

CLOGGED PIPE GOING TO THE PUMP - A clogged pipe from the skimmer, suction line or main drain reduces the amount of water to the pump which can reduce water flow to the pump and create low water pressure out the return lines.  

Solution: Push a stiff wire down the skimmer or suction ports to see if you have a clog near the entrance. If there are no clogs there, you may have to get a pool professional to come in to check your pool pipes.

Step 9

PUMP IS TOO SMALL - If your pump's size was calculated for you initial pool system and you have added more equipment onto that system, you may have exceeded the pump's capability to supply the GPM that is now required. Also, if you have moved your pump significantly further away from the pool, which required more pipe, you may have increased water resistance in the pipes that exceeds the pump's capability.   

Solution: Replace the motor in your pump. Note you may also have to increase the size of your filter if it won't handle the increased GPM water flow. See our guide on "How To Replace the Motor on Your Pool Pump".

Step 10

BAD PRESSURE GAUGE - Pressure gauges on top of the filter do go bad. Your apparent low pressure reading may be due to a faulty gauge.

 Solution: Replace the pressure gauge. See our guide on "How To Replace a Pool Filter Pressure Gauge on a Cartridge Filter".


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Inyopools  Posted: 03/22/2018 10:51 AM  Latest Inyo Product Specialist

Hello KoalaTea Jarred - The most common culprits of an air leak are pump lid o-rings, plumbing fittings, valves, and drain plugs. Pump lid O-rings are a habitual offender of air leaks. The O-ring can expand or deteriorate over time and allow air to enter the pump. You can try applying a silicone or Teflon lubricant to see if it helps, but often times it needs to be replaced. Plumbing fittings will also draw air. A popular technician trick is to use burning incense. While the pump is running, wave the burning incense near suspected areas. The smoke will be drawn in, if there is a leak. Check the fitting on the pump intake, the couplings and elbows. Cut out and replace any fittings that have an air leak. Valves can be inspected like the plumbing fittings. Diverter valves will usually have internal O-rings. These O-rings can easily be replaced to fix an air leak. Simple ball valves are not usually repairable and need to be replaced, if there is a leak. Drain plugs are found on most pumps. These plugs are usually used to drain the pump when a pool is winterized. They should be tightened firmly into the pump. Inspect the drain plug and drain plug O-ring. Replace them if they look decrepit. As far as bleeding the filter prior to the pump stopping, you can do this but hopefully the issue will be resolved from one of the culprits above.

KoalaTea Jarred  Posted: 03/10/2018 21:04 PM 

Hello InyoPools, Quick query. I have a brand new SQ1202 motor, (replaced for Sta-Rite Max E-Glas II motor) and 2 months ago I rebuilt the wet end (new: impeller & screw, diffuser, basket, and all new gokit). I've cleaned all baskets, and no clogs or flow issues. I also have a Sta-Rite - Sys 3 Mod DE Filter - S7MD72. I've cleaned the filter meticulously and all gaskets are great! I'm 99% sure my top-mounted pressure gauge is broken, as the needle is stuck, and with a brand new pump, I'd expect to see some movement. Furthermore, the pump is moving water wonderfully smooth. I have no discernable spitting leaks, and the "crawler" moves great. I think I'm fine there. The issue I'm experiencing is a constant buildup of air in the filter, followed by very tiny air bubbles out of the return jets. I'm having trouble locating the suction side leak. Does any guru have a tip or two they'd share? Please and thank you! ...and also, is it possible to bleed off the back pressure just prior to stopping the pump, in order to avoid the inevitable backflow from the filter? Thank you, Jarred

Inyopools  Posted: 03/07/2018 10:16 AM  Inyo Product Specialist

Victor - It does sound like you have a clogged filter. It may look clean but sometimes oils and chemicals build up in the pleats of the filter which are hard to remove. Before buying a new filter, try cleaning the old one chemically. See our guide on "How To Chemically Clean a Pool Cartridge Filter".

Victor  Posted: 03/03/2018 19:25 PM 

C900 filter system- I have low pressure in return jets and small bubbles. I ran the pump with no filter and worked great with no issues. Once I re-installed the cartridge the low pressure and bubbles returned. Does this mean the filter needs to be replaced? Thank you!

Victor  Posted: 03/03/2018 18:58 PM 

Low pressure and Bubbles in return jets to the pool and strainer basket chamber does not fill all the way. I have a Hayward c900 and when I removed the filter cartridge everything worked fine with great pressure coming out of jets. Once I re-installed the filter cartridge the low pressure and bubbles returned. Does this mean it is the filter cartridge that needs to be replaced?

Carmen  Posted: 01/16/2018 1:53 AM 

My pool pressure was very low at 8 psi. I Googled it and went to your website. I read several times it could be the impeller is clogged. I followed your instructions to check and clean the impeller, and sure enough a few big leaves were stuck in it. The psi immediately went to 15 psi. It was so so simple and quick to check and clean. Thank you so much!

Inyopools  Posted: 11/13/2017 14:03 PM  Inyo Product Specialist

Confused - "No flow" means something is partially blocking the water flow in your system. Make sure your filter is clean, check the skimmer and strainer baskets, and check that the impeller in the motor is not clogged (a common problem).

Confused  Posted: 11/12/2017 13:59 PM 

my pool has a reading of "ps low or no flow". What does this mean and does it affect the temperature of the pool?

Inyopools  Posted: 10/24/2017 13:00 PM  Inyo Product Specialist

Love my pool ! - 1) When you replace motors you have to look at the motor Total HP (THP) rating which is the product of the HP and the Service Factor (SF) printed on the motor label. The THP of your new 1.0 HP motor may be equal to that of your old 1.5 motor. For example, if your old 1.5 HP motor had a HP of 1.5 and a SF of 0, it had a THP of 1.5. If your new motor has a HP of 1.0 and a SF of 1.5, it has an equivalent THP of 1.5. If they both have a SF of 1.0, the 1.0 HP motor is smaller than the 1.5 HP motor. 1+) Assuming your new motor has a THP reading of 1.0 and is smaller, you may have to reduce the impeller size as you suggest, but not always. See the parts list for your motor. Sometimes two adjacent motor sizes (1 and 1.5 HP) use the same propeller. 2) The smaller motor probably would not cause the pressure gauge to read 10 points higher. Try cleaning your filter or replacing the gauge.3) A smaller pump would reduce water flow which could reduce cleaner performance.

Love my pool !  Posted: 10/22/2017 18:32 PM 

3 questions please ! My pool's 1.5 HP motor, quit / died. A pool service guy removed it, took to motor guy who had rebuilt it 6 years ago. No longer repairable, so he replaced it with a new motor. BUT not a 1.5 HP... new motor is 1 HP ??? Q #1 Should I insist he replace it with 1.5 HP as originally built ? My research shows going from 1.5 to 1 HP and not updating the impeller & diffuser to match the slower speed, will burn up the motor. (pool guy did NOT update impeller) Q#2 Could this be the cause of the Pressure Gauge going from 10 to staying at 20 ? Q#3 Is this why my Polaris barely moves around the pool often stands still ? (the wheels turn) The new Polaris is only 1 or 2 years old. Replaced it same time we bought new salt cell. Thank you!

Inyopools  Posted: 09/17/2017 11:41 AM  Inyo Product Specialist

TC - Check to see if your pump's impeller is clogged. That is a common problem. If you have a cartridge filter, try pulling out the cartridge and seeing if you have good pressure without the cartridge. If so, clean the cartridge or buy a new one. If you have a sand filter and haven't replaced the sand in 5 years, consider replacing the sand. Also, try blowing out the suction pipe from the pump's end using a Drain King attached to a garden hose.

TC  Posted: 09/14/2017 10:51 AM 

We have an inground pool with a side skimmer and a skimmer in the bottom of the pool. These are all plumbed back to a pump room with the filter and pump. We have lost all pressure at the filter and the water seems to "surge" when it comes in to the pump. The pool has turned very cloudy. I believe we have something wrong on the suction side or maybe debris plugging one of the lines from the skimmer? Any suggestions?

Inyopools  Posted: 08/14/2017 15:48 PM  Inyo Product Specialist

bhturnow - It sounds like you may be getting back pressure building up in the top of your tank due to a suction air leak. If you open up the relief valve on top of the filter when the pump is running, is air released and does your pool pressure go back up. Or when you turn off the pump, do you have a water surge back to the skimmer? These are symptoms of back pressure build up due to a suction leak. See Step 7 of this guide. To locate the suction air leak, try blowing smoke around each of the suction side connection and the pump cover. If you see smoke getting sucked into the system, you’ve found your leak. People have also brushed a soapy solution around the connectors to see if little bubbles are sucked into the system.

bhturnow  Posted: 08/11/2017 14:31 PM 


RE: Hayward DE Filter and Hayward MaxoFlo 1.5HP pump

Any ideas on why my filter starts off great with pressure but then after 30-45 minutes the pressure lowers. It goes from about 13psi to about 22psi and you can feel the lower pressure. I have completely disassembled both the pump and filter and still no luck. I soaked the DE filter for 13 hours and cleaned it well. There are no clogs anywhere. I am lost. The pump sounds great and I even changed the impeller seal to be safe. The pump is not overheating. Thank you for any tips. Be well. Brad

Inyopools  Posted: 08/07/2017 11:05 AM  Inyo Product Specialist

TjaX - It sounds like you have an air leak on the suction side of the pump. A leak on the outflow side would not create air in your filter. They'd squirt water out. To find your suction air leak, try blowing smoke around each of the suction line connections. You would see some of the smoke being sucked into the leak. If you haven't replaced the O-ring under your pump's strainer cover for a while, I would suggest doing that.

Inyopools  Posted: 08/05/2017 13:10 PM  Inyo Product Specialist

Anonymous (local store) - Unfortunately, we do not have a pool company near Indian Falls, Maine.

TjaX  Posted: 08/04/2017 15:13 PM 

Whether valve is set to Skimmer or Floor Drains, water rushes into pump, but threw the clear cover to the pump the water doesn't fill the chamber completely and there is air in the pumps filter basket. Appears to be pulling in water, but I can't seem to get any pressure in my filter. I have primed and it seems like its flowing, but after purging the air from the top of the filter and closing it, it still doesn't build pressure, and I have to let the air out again. It seems like I have a air leak on the outflow side? No visible pressure on filter (gauge is good), flow only comes out of 1 out of 3 return jets, but there is flow.

Anonymous  Posted: 08/02/2017 11:40 AM 

Do you have any pool companies near island falls maine

Inyopools  Posted: 07/20/2017 11:22 AM  Inyo Product Specialist

Kim - If you upgraded your pump to a larger size, your filter may not be larger enough to handle the water flow. Check the GPM rating on your filter to make sure it is at least as high as the pump GPM rating.

Inyopools  Posted: 07/19/2017 10:15 AM  Inyo Product Specialist

Kish - Try backing off to 80% DE that you add after a backwash, and if your filter has a breather tube down the center of the tank, make sure that tube is not clogged.

Kim  Posted: 07/17/2017 23:34 PM 

My pool pump is new an recently attached to a 16 by 42 intex pool . Its pushing water out fast but the suction in the pool is weak an not sucking in dirt an not keeping my pool clean . My finger dont even stick cause the suction is so weak is this normal

Kish  Posted: 07/17/2017 14:45 PM 

I have a Hayward EC40 Perflex DE filter with a 3/4 HP motor for my in-ground pool. The filter's fingers were pretty dirty, so I had them acid washed and clean. This has improved the water pressure, however, it only runs for about 5 minutes before the pressure increase from about 10 psi to over 40 psi and the circulation stops. After bumping the filter and/or back-washing, the same symptoms re-occur. Help!!!

Inyopools  Posted: 07/13/2017 13:08 PM  Inyo Product Specialist

Autumn - If I understand you correctly, air got into your skimmer while you were cleaning it out, causing your pump to lose prime and water flow stopped. You just need to reprime your motor. See our guide on "How To Prime a Pool Pump".

Autumn  Posted: 07/12/2017 14:37 PM 

My her stopped blowing as I was cleaning out the skimmer basket. At some point I did stop water flow from going into the skimmer, how do i fix it so the jet comes back on?

Sonal  Posted: 07/03/2017 0:37 AM 

Your advice is spot on. I went step by step, simplest solution to the most complex and within a week, got my pool from a swamp that had poor pressure to clear with normal pressure. Your advice and tips have definitely saved me hundreds if not a thousand or so. I rebuilt a couple valves and learned tons in the process. Thank you for the help and allowing me to have the pool back for the summer!

Inyopools  Posted: 06/30/2017 12:22 PM 

KatieRI - Sounds like you have a suction leak at or before the pump that is letting air in the tank and causing a gradual buildup of backpressure. See our guide on "How to Identify and Correct Air Leaks". Many filters have a breather tube down the center of filter tank to relieve this air pressure. Make sure that tube is clear. The glug glug noise is common. Also, it is normal to see large bubbles at the returns when the pump is first starting up and purging air from the system pipes.

KatieRI  Posted: 06/28/2017 20:57 PM 

We were having an issue with low pressure and the flow of water filling the pump basket was too weak. (DE filter) I thankfully came across your advice to clean the impeller- full of debris. Also backwashed. Seemed to fix the problem! Except it was only temporary...

Now the vacuum suction seems weak. When the pump is on recirculate the flow of water into the pump basket is forceful and water splashes against the cover. If we quickly turn to filter, this flow lasts for a while, but then the flow seems to lessen and water no longer splashes against the cover- there is just a constant flow of water. Same happens when vacuuming. If the pump is turned off for a few minutes and we try to start on filter, the flow never gets going well enough to create good pressure. Why would it work well on recirculate but not on filter?

A couple of other things that might be worth mentioning: 1.) When I removed the pump basket cover to clean out the basket, I hear a "glug, glug, glug" as the water level goes down. (Not sure if that's normal or if it should flow smoothly.) 2.) There are also bubbles that come out of the jets, and this has been that way for years and things have always worked fine. When the pump first starts there are big bubbles, then tiny bubbles once the air clears. 3.) We open the air relief valve when the filter starts until we get the stream of water, then we close it. It doesn't seem to take long (5-10 min) before there is more air to be released. (Also not sure if this is normal?) Thank you for your helpful advice!

Inyopools  Posted: 06/24/2017 12:37 PM  Inyo Product Specialist

Anonymous (low pressure). When you shut your pump off do you have a surge of water through your pump and out the skimmer. If so, you may have backpressure building up in the top of your filter and impeding forward water flow. This back pressure is usually due to a suction leak in your system at and before the pump. Also, most filters have a breather tube going up the center of the tank to relieve some of this pressure. Make sure that tube and the screen at its top are clear.

Anonymous  Posted: 06/22/2017 12:03 PM 

after opening my pool, everything appeared fine. Then one morning the pool was so cloudy you could not see the bottom at the deep end. For the last 10 days, at my pool supply company's suggestion, after they tested my water, I have added clarifier, shock, soda ash, and stabilizer. Now for more than 10 days my pool is still cloudy. I have a de filter. I have cleaned the grids in the filter many times during this process. Sometimes i have added de and other times i did not. After backwashing and or cleaning the filter, the next morning my water out of the jets is flowing at about 20% and my pressure gauge on the filter is much higher than normal. so i have either cleaned the filer again or backwashed, the proper water would flow out of the jets but within a couple of hours the water would slow back down and the pounds of pressure would rise again! Whats going on?

Inyopools  Posted: 06/20/2017 10:36 AM  Inyo Product Specialist

Sherri - If you have a surge of water flowing back through the skimmer when you turn the pump off, you may have backpressure building up in the top of the filter. Look for suction air leaks in the piping before your pump. See Step 7.

Inyopools  Posted: 06/19/2017 17:31 PM  Inyo Product Specialist

Val - Check your pump's impeller to see if it is clogged. Then look at any repairs you may have made recently on the suction side of your pump to see if you have induced any suction leaks.

Val  Posted: 06/19/2017 13:37 PM 

We have a pool & spa with a Caretaker 99 in floor pop up cleaning system. Noticed a couple months ago that pop ups come up and go right back down, and flow from spa to pool when cycling is much lower than normal. Transformer for rotation control had been tripping, so it was replaced and filters were cleaned last week. Problems remain. Solar system was replaced at end of last year. Wondering if problem could be related to that or ???? Any suggestions would be much appreciated.

Sherri  Posted: 06/18/2017 23:22 PM 

My pump is not working correctly. I have had a repair man come and he says it's fixed but An hour later same problem. Pump seem to work ok for about an hour then it losses all pressures. Water seems to be at the top of the pump basin. If I remove the top of the pump let the water run out it then turn it back on it will work properly for an hr or so. The easy fixes have been checked. Skimmer basket and pump basket are all clean and the hoses are not plugged. Like I said it will work for a bit. Pool guy had no idea. Would you have any suggestions?
Thanks Sherri

Inyopools  Posted: 06/11/2017 22:46 PM  Inyo Product Specialist

inultus - You might have better luck using a metal electrical fishing line than a plumbers snake. It may be easier getting around the 90-degree elbows. Also, check your pump's impeller to see if it is clogged. See our guide on "How To Clean Out a Pool Pump Impeller". That is one of the more common solutions to resolving low water flow.

inultus  Posted: 06/10/2017 1:33 AM 

Firstly, thsnk you very much for all or your answers here. I have several problems with a 21K inground pool, but I think they are all related. Bubbles from outlets. Intermittent low suction when using manual vacuum (I have an Aquabot but vacuum manually when needed). No leaks from pressure side, no heater and no solar in this system. Pump just a few years old, filter just slightly older. Unfortunately I had a tree with big roots growing near underground pipes. I have since cut it down and done my best to kill the stump. I will certainly check again for the suction side issues that I can diagnose. I wondered if you had other suggestions? Also, when checking for a blockage in from skimmer piping is it ok to use a manual drain snake (for use in household plumbing), or should the coat wire method be all that's used? Thanks, and cheers from Michigan where we only get to use our pools a few months per year, so time is always valuable.

Inyopools  Posted: 06/08/2017 22:01 PM  Inyo Product Specialist

DMS - It sounds like you are good up to the filter. Try running the MPV in "Recirculate" mode. This bypasses the filter and returns water back to the pool. If you have low pressure, there is a blockage in the pipes after the filter. If not, there is a restriction in the filter. Does the water flow freely in "Waste" mode? Was your spider gasket damaged when you took apart the MPV?

DMS  Posted: 06/06/2017 6:31 AM 

25,000 gallon in ground vinyl pool with Hayward 1.5 HP pump, not sure what model the sand filter is. Started out with low pressure, now almost no water returning to pool.
Here is what I've done
1. replaced skimmer/bottom drain pipes from where they come out of cement prior to pump.
2. pulled motor apart and checked impeller and not clogged and run fine.
3. disconnected pipe between pump and filter and turned on pump, water comes out like a fire hydrant.
5. Took apart and inspected multiport valve for blockage.
4. currently draining the sand filter and plan is to vacuum out sand, reconnect filter and run sand free to see if it is possibly clogged filter (is this a bad idea?)
Thoughts on what to look at next?

Inyopools  Posted: 06/04/2017 23:31 PM  Inyo Product Specialist

Bama Bill - First check that your pump's impeller is not partially clogged. See our guide on "How To Clean Out a Pool Pump Impeller". Then, if you have a main drain/skimmer diverter valve, try shutting off some of the water flow from the drain to increase the flow to the skimmer or suction port if you have one.

Anonymous  Posted: 06/04/2017 15:30 PM 

Inground pool almost completely looses pressure when "backwashing." Trying to rectify a mustard algae problem and cannot vac to waste, as instructed due to loss of pressure. Pool works better when not on backwash, but then dirty water gets pumped right back into the pool clouding up water. Very frustrated....

Inyopools  Posted: 06/04/2017 11:38 AM  Inyo Product Specialist

Barbara - Check to see if you have a clogged impeller. That is a common problem especially if you had a lot of debris in you pool when you opened it. See our guide on "How To Clean Out a Pool Pump Impeller".