How to Correct Low Water Pressure in Your Pool System

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How to Correct Low Water Pressure in Your Pool System

WRITTEN BY: Inyo Pools

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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.

Step by Step

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Step 1

Your pool’s plumbing system can be broken into two sections: the Suction-Side and the Pressure-Side. The Suction-Side of your pool includes the skimmer, main drains, plumbing, and any other equipment like diverter valves, up to the strainer housing of your pool pump. The Suction-Side is the portion of the system, your pump is pulling the water toward it. The Pressure-Side of your pump begins at your pump’s impeller; this is when the pump’s pulling becomes a pushing force to move the water through your pool filter, heater, chlorinator, and all the associated plumbing until it returns to the pool via the return jets.

Step 2

Low Water Level (Low PSI) - The water level should be at least halfway up the skimmer door's opening. A low pool skimmer water level will allow the skimmer to gulp air as your water ebbs and flows caused by the pump running or activity in the pool.

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.

Click Here to View Replacement Skimmer Parts

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.

Click Here to View Replacement Pump Parts

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.

Click Here to View our Liquid Filter Cleaner

Click Here to View Replacement Filter Cartridges

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".

Click Here to View Replacement Pump Parts

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".

Click Here to View Replacement Pump Parts

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.

Click Here to View Diverter Valve Parts

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".

Click Here to View Replacement Pool Pump Motors

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".

Click Here to View Replacement Filter Parts

Comments

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(241 to 280 of 373)

rrtresp28 Posted: 6/7/2016

waterway sand pump. in filter mode water flow is good for about 15 mins. Then flow is decreases a lot. No leaks found new sand. All other modes work great. have had unit apart and cant find anything wrong.
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Anonymous Posted: 6/7/2016

Hi I have a Hayward DE4800 which continues to get high pressure after a few days even after thoroughly washing grids and restarting. When I run the pool in recirculate everything appears fine, which leads me to beleive there is not a suction side air leak. Could it be a clogged flex air relief assembly? Any help would be appreciated it. One more question, when the pump is shit off, should it remain full of water?
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poollover Posted: 6/6/2016

Just got a brand new salt water sand pump for above ground pool but every time we try to turn it on it says low water flow. There is no water flow at all and we have checked please help
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InyoPools Product Specialist Dennis R. Posted: 6/2/2016

Joe H - Do you have suction air leaks in the pipe from the pool to the pump? If you do and you ran for 2 hours, you might have run with air in your system. The motor may have lost prime and you might have some motor damage. On a happier note, check that pump's impeller was not clogged with debris or a small toy.
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Inypools Posted: 6/2/2016

Ed - Check for a clogged impeller. Then, if your filter has a breather tube going up the center of the tank from top to bottom, make sure it is not blocked. You could have air building up in the top of the tank creating back pressure.
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Joe H Posted: 6/1/2016

I have 24' round above ground, with Haywood pump. It's 8years old and haven't had any problems. I opened the pool but when I turned it on, I had leaks in the PVC pipe from pump to filter (both sides). Also, have leak in pipe coming out of filter. With all that, I start ou with good pressure for an hour or 2, but then the pressure drops off big time. Had a pool guy come out, and he said he could not fix it. Any suggestions?
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Ed Posted: 6/1/2016

My pressure rises on the gage but the water flow becomes slower overnight!! Tried multiple wash etc. any hints to this issue? All skimmers and lines are clear.
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InyoPools Product Specialist Dennis R. Posted: 5/31/2016

MS - I assume that when you say "connect to clean" that you are connecting a suction cleaner into your system and when you connect, your motor loses prime. If this is what you mean, it sounds like you have a bad suction leak in your cleaner line. Hold the cleaner hoses completely under water to see if the leaks are in the hoses. If so, replace one or more hoses. Otherwise, you may have a leak underground in your cleaner suction line.
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InyoPools Product Specialist Dennis R. Posted: 5/30/2016

richardH - One of our customers had a similar problem. He found that the hub in the bottom of the standing pipe of the sand filter was cracked and was letting sand in and clogging the laterals. You might check this hub and standing pipe.
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InyoPools Product Specialist Dennis R. Posted: 5/30/2016

Lisa - From your discussion, I would have to say that your problem is in the multiport valve, but I don't see where. Does the "Rinse" setting work? If it does, nothing makes sense. Rinse is just like backwash except the water is going down through the filter and out the waste port rather than up through the filter before going out the waste port. Did you leave at least 6" of space at the top of the tank?. Give Hayward a call on this on at 866-772-2100. They might have an answer.
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InyoPools Product Specialist Dennis R. Posted: 5/30/2016

Rinse cycle – There should not be any damage. During a Rinse cycle, the pool water is going down through the sand, but instead of going out the return port as it would in Filter mode, the water is exiting the Waste port. Your only negative should be dumping pool water for 2 hours.
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InyoPools Product Specialist Dennis R. Posted: 5/30/2016

Scott – If your DE filter has a breather tube going up the center of your filter top to bottom, check to make sure it and the screen cap are not clogged. If it is clogged, you may have air building up in the top of the tank causing backpressure.
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MS Posted: 5/29/2016

I have a hayward de filter, every time i connect to clean, my pressure drops and i lose suction and there is no pressure on the water going into the pool. Usually I have to turn off and bump the filter and pressure returns. But when i go to clean, the same thing happens. The filter and skimmer are clean. Not sure where else to go.
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InyoPools Product Specialist Dennis R. Posted: 5/29/2016

Hoses reversed – I would take the multiport valve apart to see if it is clogged with sand or if the spider gasket is damaged. See our guide on “How to Replace a Spider Gasket on a Multiport Valve” for instructions.
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richardH Posted: 5/27/2016

I have a problem that i cant track down. I have an above ground pool with a Hayward pump and sand filter. When the i have it set in FILTER mode, it pumps really strong for about 30-45 minutes. After that, it barely has any pressure blowing thru the return line. When i have it set in any other mode...recirculate/backwash/rine etc, it never looses presure. I have checked for leaks, replaced sand, checked impeler, checked for clogged lines...nothing. never any air in pump basket. Pump works perfect in every mode except FILTER mode. After about 30 min, acts like its not even pumping. Im lost here. Any ideas?
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Lisa Posted: 5/26/2016

I have a Hayward sand filter S180t. Every year the lateral assembly cracks. This year was no different. It has been replaced along with the multi valve assembly due to a worn spider gasket. So now the problem, the filter will not backwash at all. Waste works fine. Water is being pulled from the pool into the pump then out the filter. Filtration seems fine as well. Backwash, nothing moves at all. Am at a loss here. No clogs in the hose from skimmer to pump, no clog in pump. Also, pump basket cover and gasket new last summer. Any help is appreciated.
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Anonymous Posted: 5/25/2016

I left the filter on the rinse cycle for at least two hours with the filter running. Wondering what damage I may have done
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scott Posted: 5/25/2016

I have a Hayward DE filter and pump (above ground). After I prime it, good water pressure exists, nice flow into pool. Runs at about 12-14 psi. After only 10 minutes, it climbs to about 18-20 psi and the flow into the pool is decreased greatly. I think there might be air getting into the system as there seems to be a lot of bubbles in the pump basket, but not sure. I had one connector replaced that seemed "old", but the other connections seem fine. I can't be sure if it's an air issue or something else. Note: after I backwash it, it only works for another 10 minutes before the same issue. I also noticed that if I DONT backwash it, but just open the air relief valve, i can get it to work again for about 10 minutes....so it seems odd that opening the air valve will get me a steady stream even if I don't backwash it....although only for 10 minutes. help???
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InyoPools Product Specialist Dennis R. Posted: 5/24/2016

low pressure - Check to make sure the impeller in your pump is not clogged. Then check that the O-ring on the strainer cover is in place and not bulging out. If the O-ring is old, you should consider replacing it.
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Anonymous Posted: 5/24/2016

We accidentlly put the hoses wrong on our sand filter and ran it for about 5 mins and realized they were backward. Now when we turn the filter on and have the sand filter on filter mode no water comes out of the hose. Can this be fixed
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Anonymous Posted: 5/23/2016

My sand filter won't keep its prime. The strainer basket fills up with air. I've also tried on recirculate without any luck. Everything seemed to be working fine as of yesterday. I turned the pump on today to backwash and noticed the water wasn't very forceful. Now I can't seem to get the pump to work properly.
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InyoPools Product Specialist Dennis R. Posted: 5/23/2016

frustrated - I would guess that your problem is more with your filter than your pump especially if it works in recirculate mode. If your DE grids haven't been changed for a long time, you might consider replacing the set. Even if they look clean, oil and chemical can build up on the grids that won't wash out. Also, when you clean or backwash the grids, only add about 80% of what the install instructions call for. It's difficult to get all the DE powder out of the system when cleaning, and you may end up with too much powder on the grids. Too much powder creates a higher resistance to water flow.
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fustrated Posted: 5/21/2016

I just opened my pool, which was covered with a loop-loc cover. It was quiet dirty. I have lost return pressure frequently. I decided to open the DE filter. It was very dirty. I continued to loose pressure and have opened the filter 4 more times, each time being with less dirt. I cannot maintain a reasonable return pressure for more than a few minutes even after just cleaning the filter. I can maintain the pressure with the multi-valve set to recirc. Is it possible that the pump is starting to fail and cannot push the water against the resistance of the filter/heater and salt generator?
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InyoPools Product Specialist Dennis R. Posted: 5/17/2016

dmarieh5 - That much air in your strainer basket is generally due to problems at the skimmer. Take the cover off your skimmer trap and see if it's getting a solid flow of water. Is the pool water level too low or is something blocking the skimmer weir door so that it is not able to float?
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dmarieh5 Posted: 5/17/2016

I need some advice..i dont have any suction from my skimmer. I've tried a bunch of tricks but nothing seems to work. My PSI is 5-8 and i can visually see air in the filter at the pump. I know its not the impellar because i just had that fixed. Any thoughts on what is causing this and how to fix it?
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InyoPools Product Specialist Dennis R. Posted: 5/16/2016

Tia - If you haven't replaced your filter grids for 5 years, it may be time to change them. They may look clean, but over time, they get clogged with oils and chemicals and need to be replaced.
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Tia Posted: 5/13/2016

We have a Pentair DE filter that is almost 5 years old. We're having an issue that the pressure on the filter will not go below 20. It's supposed to be about 12-15 but it goes right past that and up to and over 20, sometimes 30! We've cleaned the fins, put in new DE, backwashed, cleaned the baskets.. nothing. I'm about to drain it and fill it in!

Any suggestions??
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Anonymous Posted: 5/12/2016

Thank you so much for the wonderful advice. We had low air pressure in our pool. We read your information to look at the propeller for debris. Walla!!! Cleaned it out and working perfectly!!! Again thank you so much.
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InyoPools Product Specialist Dennis R. Posted: 4/26/2016

traderjack - I assume you have a C-1750 model Star Clear Plus cleaner. You are right. 28 psi is too high. See what the pressure is if you run the filter without a cartridge. If it is still high, your problem is somewhere else. Make sure the breather tube that runs from the top to bottom of the tank is in place and not kinked or clogged. If that tube is not working, you will have backpressure buildup in the top of the tank.
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traderjack Posted: 4/26/2016

Looking for help!I have a Hayward Star clear cartridge filter. I just replaced the cartridge with a new Pleatco PA 175. My pressure gauge jumped from 18 psi with the old filter to 28 psi. I also added a new Paramount six port water module to replace the old one which wasn't working. The module seems to work fine with about 16 psi as each pop up cycles. My pool lady says the filter pressure should have gone down instead of up. What could be wrong? Your help will be most appreciated.
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InyoPools Product Specialist Dennis R. Posted: 4/25/2016

JT - Sounds like you may have a backpressure issue. If you have a side mount sand filter (multiport valve on the side) check the breather tube that goes from the top to the bottom of the tank. If it is clogged. pressure may be building up at the top of the tank causing backpressure to the flow of water into the tank.
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InyoPools Product Specialist Dennis R. Posted: 4/25/2016

JB - Check that they put the right "feet" on your Navigator. There are different feet for concrete and fiberglass. Then, if you can, partially shut off the flow from the skimmer or main drain to get more flow to the cleaner. Lastly, check that your pump impeller is not partially clogged. See our guide on "How To Clean Out a Pool Pump Impeller".
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JT Posted: 4/24/2016

I have a problem with my Hayward sand filter. The pressure gauge rises from 13 psi to 18-20 psi, but the water flow return to pool drops significantly. I changed the sand in the filter and checked the laterals and center pipe. I could see no problems other than the laterals had a small amount of sand stuck in them.When I backwash and rinse the filter it runs good for about 20 mins. But then has the same problem. It's an above ground pool with 1.5 HP pump. Any ideas?
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JB Posted: 4/23/2016

I have a Hayward Navigator. Leslies replaced the "feet" and the "Flappers"on the side. Now it will not go up the walls. It's fine on the bottom just stops at the curve to the wall
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InyoPools Product Specialist Dennis R. Posted: 4/18/2016

Al - After you change your filter's sand, you should see a significant drop in pressure at your pressure gauge. But if you are also seeing a drop in water flow, like your cleaner is moving a lot slower, then you have a problem. When you replaced the sand did you leave at least 6" of open space at the top of the filter? Did you use sand processed for pool filters? Try backwashing and rinsing a couple of more times to see if that helps. If your filter has a breather tube coming up the middle of the tank, make sure that is not clogged. See our guide on "How To Change Sand In a Sand Filter" for other possible suggestions.
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Al Posted: 4/15/2016

replaced the sand in my filter and now it has half of the pressure as before. Still works but does not nearly as powerful. Any ideas?
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InyoPools Product Specialist Dennis R. Posted: 4/11/2016

low pressure - It sounds like you may have back pressure building up in your filter system. See the second half of our blog on "Correcting Low Water Pressure in Your Pool System". If you have a breather tube running up through the middle of your filter, make sure it isn't clogged. It relieves the pressure buildup in the top of your filter. Also make sure you have at least 6" of space between the top of your filter's sand and the top of the filter tank. If you haven't replaced the sand in the last 5-7 years, it's time to change it.
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Anonymous Posted: 4/11/2016

I have extremely low pressure at my return when the sand filter is set to filter. If I backwash my Sand filter for a few minutes and put it back on filter it runs OK for 15 to 20 minutes. If I put it on recirculate everything works perfectly as far as recirculation goes and the pressure on my return is great but when I change it back to filter once again it works OK for 15 to 20 minutes then slows back down.
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InyoPools Product Specialist Dennis R. Posted: 4/11/2016

stumped - You may have a partial blockage in one or more of the suction pipes. Small toys often get past the skimmer basket when cleaning and get stuck in the first joint. Try pushing a plumbing line through the skimmer port(s) in the first part of your skimmer suction line. If you have unions at the pump, try blowing out the suction lines to discharge any possible debris back into the pool. You seemed to have covered other options.
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stumped Posted: 4/7/2016

I have a DE filter and a pressure side cleaner, each with a pressure gauge. The pressure on both is low. The DE gauge used to show about 12-15, the cleaner gauge about 15. Now they are about 8-10 and 10 (so the cleaner is not working well). I have a bottom drain and two skimmers. I tried switching the valves to draw from one at a time. Each resulted in a lower pressure than having all three open, which I expected, but none was terribly low, so I don't think there is a blockage in any one of them. There is no air in the pump cover so I don't think it is sucking air. DE filter was just disassembled to replace some torn grids. I took the pump was apart - the impeller was clean. One O-ring was broken so I replaced both O-rings in the pump, no change. Changing the MPV to recirculate made no difference. I'm stumped; any idea what else it could be?
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