How to Correct Low Water Pressure in Your Pool System

WRITTEN BY:  Inyo Pools

  3.62 out of 5 stars on 40 ratings
(Click on a star to add your rating)

Low pressure is a pool term that is often used to describe weak jets as well as a low PSI reading on the filter’s pressure gauge. High PSI readings will also cause low water pressure. A low or high PSI reading is anything outside the normal operating pressure of the filter. Weak jets, air bubbles, slow pool cleaners and weak water features are obvious signs of low pressure. This guide addresses the common causes of low water pressure in a pool.

Video

Step by Step

Top

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

LOW WATER LEVEL (Low PSI) - The water level should be at least halfway up the skimmer door's opening. If it's too low, the pump will have trouble priming and the water pressure will drop.

Step 3

CLOGGED SKIMMER BASKET (Low PSI) - 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 4

CLOGGED STRAINER BASKET (Low PSI) - 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 5

CLOGGED FILTER (High PSI) - 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 6

CLOGGED IMPELLER (Low PSI) - 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 AT PUMP (Low PSI) - The pump lid o-ring, pump intake fitting, and drain plugs are common areas to draw in air. 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

SUCTION LEAK AT DIVERTER VALVE (Low PSI) - The diverter valves in front of the pump control the flow of water from the skimmer, main drain, and vac lines. They also have seals in them that can go bad and allow air to enter the system. Again, air will cause the water pressure to drop and will lead to the pump losing prime.

Step 9

SUCTION LEAK AT PLUMBING FITTINGS (Low PSI) - Any fitting on the suction side of the system can draw air. Cut out and replace any fittings that have an air leak.

Step 10

CLOGGED PIPE GOING TO THE PUMP (Low PSI) - 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 11

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 12

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 13

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".

Comments

Top
(1 to 40 of 270)

InyoPools  Posted: 08/16/2018 16:17 PM  Inyo Product Specialist

Hello dman4227 - We recommend reading our article titled "Why Are My Pool Jets Not Working". It has a number of solutions for resolving your low-pressure issue.


InyoPools  Posted: 08/15/2018 15:21 PM  Inyo Product Specialist

Hello Texasney - Check out our article titled "Why Are My Pool Jets Not Working". Specifically, Part II of the article. This covers high PSI and low water output.


Matthew  Posted: 08/14/2018 16:18 PM 

Hello Tom - What happens if you set the filter to normal filter mode and hook up the vacuum hose? if it loses strength then i would say there is an issue with the hose. Suction hoses are susceptible to pinhole sized leaks that can trap air in the system causing drops in pressure. To test it another way, set the filter to waste without the vacuum hose attached to see the outcome. The first method I mention will save you money on water, I'd choose that one.


Tom  Posted: 08/10/2018 22:19 PM 

My inground filtration function works just fine but when I set it to vacuum to "waste" setting and try to clean the pool out, it only has a very little suction power and isnt sufficient to clean the pool. Where might the problem be ? Thank you


Texasney  Posted: 08/08/2018 17:30 PM 

Thank you. Pressure in filter strong. Outflow decreases and stays weak w/ filter in.


InyoPools  Posted: 08/08/2018 17:10 PM  Inyo Product Specialist

Hello Texasney - When you say that the pressure is low, do you mean that the pressure coming out of the jets is low or that the pressure reading on the filter gauge is low?


Texasney  Posted: 08/05/2018 21:47 PM 

Pressure way down. Took out cartridge filter. Ran w/o filter. Perfect! Stayed perfect for hours. Cleaned filter and re-inserted. OK at first, but pressure gradually dropped again. Your thoughts.....


Inyopools  Posted: 07/18/2018 11:48 AM  Inyo Product Specialist

Hello Charlene - There may be a plug on your filter valve that can be removed. That is where you would thread in a pressure gauge.


Anonymous  Posted: 07/09/2018 9:57 AM 

my problem is when I start my pool I have good suction but lose it over a short period of time. When I quickly backwash filter and then return to normal use, I have suction again. Cycle follows. I used a shop vac to blow the skimmer lines but the problem remains.


Dan Ackley  Posted: 06/26/2018 16:50 PM 

Just want to thank you for your video to trouble shoot, "Low pump water pressure". Turns out I needed to clean out debris in my impeller...never would have focused on that without your video...many thanks!!


Inyopools  Posted: 06/07/2018 14:00 PM  Inyo Product Specialist

Hello Damion - If the water is not clear, the filter may be filling up quickly and that is why the PSI rises and the jets slow down. If the water is clear, there is something wrong with the filter. This could be the sand or laterals. Check out our article titled "Why Are My Pool Jets Not Working".


damion  Posted: 05/30/2018 21:13 PM 

So... I have LOW water pressure. I have tried everything you have suggested. The thing is, when I put the filter to recycle, I have the pressure I would love to see. When the filter is running I have 20 psi and a trickle coming out to the pool. I have tried blowing the line, checked for air leaks, changing the sand, getting a new pump... (insert hysterical scream)! What am I missing? Please help. What am I doing wrong?


Charlene  Posted: 05/22/2018 16:48 PM 

We opened our pool over the weekend and primed the pump system. However, same as others posted, the system will not maintain the suction when on filter, or when vacuuming, with lots of air bubbles. I'm going to try the suggestions in this post first. My mom gave me this system (worked last year) but it does not have a pressure gauge so I am curious if one can be installed on a sand filter that did not come with one?


Inyopools  Posted: 05/18/2018 17:34 PM  Inyo Product Specialist

Are you plugging the hose directly in the hole at the bottom of the skimmer or are you using a vac plate? Do you have an above ground or inground pool? What is the PSI reading on the filter pressure gauge when the vacuum loses suction?


Anonymous  Posted: 05/17/2018 20:04 PM 

We have tried all of these things and are still having trouble with it maintaining suction when vacuuming (just with vacuuming). The vacuum will go good for about 2 minutes then it completely loses suction. We have replaced o-rings and cleaned everything out and have no idea what to do next.


Inyopools  Posted: 05/17/2018 12:53 PM  Inyo Product Specialist

Hello Andrew - That second hole in the skimmer does lead to the main drain. There is usually a float valve or flapper that controls the suction to the main drain on that hole. However, plugging that hole would not correct your problem. Try using a vac plate instead of plugging the vacuum hose directly into the skimmer hole. This way the pump would still be able to have the flow from the main drain and it will hopefully receive enough water.


Andrew  Posted: 05/14/2018 9:48 AM 

Well, I don't seem to have a diverter valve. I have one line only above ground going into my pump. There is a valve on that just before the pump. I have played with it a bit, but I figure that closing it would stop all water flow entirely. I am plugging my vacuum hose directly into the suction hole in the skimmer. I have a second vacuum (Barracuda) with its own hose, and they both have the same problem, so I don't think it is the vacuum hose that is drawing in air. There is a second hole in the skimmer with no suction (I think that goes to the main drain?). Should that hole be covered? There is no suction problem in my system at all when the vacuum hose is not plugged in, and I don't lose any water in the pool. Thanks!


paul  Posted: 05/13/2018 20:44 PM 

I had 2 pressure problems. The gauge showed 15 all he time, even closing the outlet valves to the pool. The pressure going to the pool was very low, auction seemed good. The heater also wouldn't work as the pressure switch wouldn't close. Tried all the pump/Line checks.... Almost bought a new switch. Then I finally saw the inlet arrow to the heater and just swapped the 2 houses to the heater and VOILA!!! FULL PRESSURE, and the heater worked properly now as well.


Inyopools  Posted: 05/09/2018 16:25 PM  Inyo Product Specialist

Hello Andrew - There should be a diverter valve near the pump that controls the flow from the skimmer and main drain. You'll have to test the valve to see which lines it is controlling.


Andrew  Posted: 05/09/2018 11:12 AM 

Thanks for the quick reply. You guys are amazing! As far as the main drain suggestion, I am not quite sure what that means. If I am not mistaken, the main drain is at the bottom of the deep end. How would one open the main drain slightly? Thanks again.


Inyopools  Posted: 05/09/2018 10:45 AM  Inyo Product Specialist

Hello Andrew - A leak detection company would have to be called in if it is underground. I would exhaust every other avenue before you go that route. Try opening up the main drain slightly. This will ensure that the pump is receiving enough water while you are vacuuming. Make sure the vac hose is clear of any air before you vacuum. Clean the filter and make sure the PSI on the gauge is staying at the normal operating range. Lastly, check for any suction side air leaks; pump lid o-ring, valves, couplings, unions.


Andrew  Posted: 05/09/2018 10:32 AM 

I have the same problem as Florida Pool Boy below. Complete loss of pressure only when vacuuming. I had the same problem when I opened last year, and it gradually resolved itself over the course of the season. But I have the same thing happening this season and I am unable to vacuum at all. I have an inground concrete pool. I am worried that the pressure change is causing an air leak somewhere underground because I can't see anything wrong above ground. Any recommendations for a next step? Thanks!


Inyopools  Posted: 05/04/2018 16:35 PM  Inyo Product Specialist

Hello Eric - If the pool water is not clear, your filter is probably filling up quickly and that's why the water flow is dropping. Check out our article titled "Why are My Pool Jets Not Working?"


Eric  Posted: 05/03/2018 10:15 AM 

I have a loss of flow only when in the filtration setting on the multiport valve. It is fine and water flowing strong when in the recirculating mode. Had this problem last year. Replaced the multiport before opening pool this year. Still the problem. I change sand yearly. Checked all orings. No leaks. Took apart the laterals/ fingers and scrubbed them out with a toothbrush and found nothing. PVS pipe in center is fine. Pump is replacement only 1 1/2 yr old. Also it doesn't change sound or speed when I change settings either. Doesn't sound like and change. Pressure or flow will slow in hours. Odd thing is that if I back wash and rinse a few minutes it corrects problem for about 5 hrs. AS I said new sand yearly, new port and laterals are fine. What gives!


Inyopools  Posted: 05/02/2018 13:53 PM  Inyo Product Specialist

Hello FloridaPoolBoy - When the hose is plugged into the skimmer, there is a reduction in flow and the suction pressure will build. This will amplify potential problems in the system. Check the pump lid o-ring. If it is cracked or disfigured, replace it. Try lubricating it if it looks ok. Also, check the hose going from the pool to the intake of the pump. Increased suction pressure on an older hose could cause it to collapse. I would also replace any hoses that have a hole.


FloridaPoolBoy  Posted: 05/01/2018 15:16 PM 

Quick question regarding a loss of pressure and vacuuming. I just unwrapped my pool from the winter, and Im working on getting it summer ready. I'm losing all my pressure when I go to vacuum the pool. This is a problem I have never had, and could use any advice. When I turn on the pump (sand filter, above ground pool) my PSI gauge shows 8psi which is normal for my pool when the filter is clean. I can let it run for hours with no loss of pressure. When I attach the vacuum hose to the intake I have an immediate and complete loss of pressure. I take the hose out of the intake (the only one this pool has), reprime the pump, and I'm back to 8psi. I've verified the hose was empty of air by submerging it in water and working all the air out. I even went so far as putting a hose with a clog buster on one end and pushing the air out under water just to be sure all the air is out. Again when I connect it I lose all pressure. I did find a small 1cm slice in the hose, but if that portion is submerged under water I can't image it would cause the lack of suction. Even if it were above the water line there is no way it's drawing enough air to cause the pump to drop to 0psi so suddenly. I also snaked the hose to make sure there was no blockage in the line. Maybe it's time for a new hose, but I don't see how that would change anything. Any thoughts at all on the next steps I should take? Thanks guys!


INYOPools  Posted: 04/24/2018 13:27 PM  Inyo Product Specialist

If your main concern is a sucking air leak, the quickest and easiest way to find it would be the "smoke trick." With the pump running, use a lit cigarette or incense stick for smoke, wave the smoke source close to the full length of exposed pipe including tees, valves, joints and pump housing. If there is a suction leak the smoke will be drawn in.


Scott  Posted: 04/24/2018 10:23 AM 

Hoping you can help with a pump suction issue; our in-ground pool includes a spa that is isolated during use with valves at the suction side of the pump. Unfortunately my wife closed ALL pump intake valves in error and our Pentair variable speed pump deadheaded for a whole day prior to discovery. Pump motor sounds like is still running fine, I replaced the mechanical seal and housing gaskets for good measure and everything seems to be working properly with impeller, etc. Now having problem with suction / cavitation; barely enough suction to make the vacuum move on its own and lots of air, trouble priming. I suspected a leak in the intake piping since piping got hot and even turned a little grey during the deadhead. To diagnose and confirm, I ran simple temporary PVC piping (same size) directly from pump intake to pool and bypassed the intake system, valves, etc. For some reason the pump can't even pull water directly from pool into the pump, even though motor sounds fine and impeller, volute, etc seems to run properly. Any ideas on what I should look at next or what my problem might be?


Inyopools  Posted: 04/12/2018 14:26 PM  Inyo Product Specialist

Hello Arizona Mom - If none of the steps in this guide worked, check out Part 1 of the blog titled "Why are My Pool Jets Not Working". Another issue could be the plumbing. Check out the blog titled "How to Fix Priming Problems in Your Pool Plumbing".


Arizona Mom  Posted: 04/11/2018 17:45 PM 

Have been working with Hayward and their Preferred warranty company. My pool pump was working fine and everything worked up until I received a drive Error on my Ecostar. They repaired this under warranty. Now there is a problem with basket priming and the Suction side jandy does not even move in the pool. They have been her twice to try to fix. I am at my wits end. What could be the problem?


Inyopools  Posted: 03/22/2018 10:51 AM  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!