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How to Correct Low Water Pressure in Your Pool System

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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.



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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 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

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(201 to 240 of 373)

 Posted: 2/19/2017 

Thanks for the tip. I had rebuilt the 3-way valve controlling flow between the pool skimmer and the sweep because the sweep was behaving erratically sometimes working and sometimes not. And the valve was 15 years old anyway. After I finished there was little improvement. Today the filter pressure had dropped to 6lbs when normally between 15-20. The pump also sounded funny and I began to think I needed a new pump. Instead I read this tip, cleaned the impeller and all is now normal. However, I was surprised because it didn't seem as if I removed very much debris. The moral is it doesn't take much to disrupt the balance of the impeller or disrupt the flow. Thanks for the tip!
 Reply

Anonymous  Posted: 2/7/2017 

I will file it in case we ever have a pool!
 Reply

 Posted: 12/26/2016 

Thanks for your advice.
I found my impeller jammed with tiny leaves.
Fixed in 5 minutes.
 Reply

InyoPools Product Specialist  Posted: 12/12/2016 

Clayton - If you have an in-ground pool, I don't know why your water level went down after you shut off the pump. If you have an above ground pool with the equipment at the base of the pool, you may have had an open line to the waste port that drained part of the pool though gravity. I don't know why your motor is humming now unless it got soak with the waste water drain off. Check the start capacitor at the back of the motor to see if that failed. See our guide on "How To Replace a Pool Pump Capacitor".
 Reply

InyoPools Product Specialist  Posted: 12/12/2016 

flow cell match - I'd be surprised if the flow cell on the Jandy c1900 could be used to replace a Polaris Watermatic flow cell, but you could give Polaris a call at 800-822-7933 and discuss it with them.
 Reply

 Posted: 12/12/2016 

Hi. I was busy vacuuming my pool with the pump on waste. I got disrupted by someone switched it off and then the following morning I saw the water level dropped tremendouslyk with the leaver still in the waste position . Now when I switch the pump on it just hums for 2 seconds but sacking a little water then it stops ducking.
 Reply

InyoPools Product Specialist  Posted: 12/5/2016 

Gert - If your water flow is good in Recirculate mode but weak in Filter, that's a good indication that your filter is clogged. Try backwashing the filter a couple of times. See our guide on "How To Backwash a Pool Sand Filter". If that doesn't work, you may have to replace the sand in your filter. See our guide on "How To Change Sand In a Sand Filter".
 Reply

 Posted: 12/2/2016 

Hi. Im a new pool onwer. When the pool setting is on filter the water pressure is very low, but when i set it to bypass it has pressure like crazy coming out into the pool. The sand seems dirty, can that be the cause? I cannot see any leaks in the system and all the baskets are clean. Thanks
 Reply

InyoPools Product Specialist  Posted: 11/10/2016 

Tim - It sounds as if there isn't enough initial pressure to rid the lines of air and get the flow going. Also, if the spa return lines are all plumbed together to where there is only one check valve, that valve might not be opening/engaging flow until the right amount of pressure is sent through the check valve. Try setting majority or all the return flow to the spa and see if that gets water flowing. Also, try cleaning the filter to see if that will increase that initial flow to the lines.
 Reply

 Posted: 11/3/2016 

Just came across your website, sorry if I'm jumping in or in wrong area....Return water is set for both pool and spa. However, there is no return to the spa every morning when the equipment fires up until I turn the spa jet blower on to "purge" the line for about 15-20 seconds. I turn the blower off and get proper return to both pool and spa for the rest of day. Frustrating and any help will be greatly appreciated. Thanks
 Reply

InyoPools Product Specialist  Posted: 10/20/2016 

John F - I'd assume that your problem is with the pump since that's all you changed. Make sure your input and discharge unions to and from the pump are tight and their O-rings are seated properly. If you pulled the motor out of the pump housing, pull it apart again and check that the diffuser and its gasket are in place. See our guide on "How A Pool Pump Works".
 Reply

 Posted: 10/19/2016 

I had an issue with my pump motor , discovered it was the capacitor. Not knowing this first, I took the pump and motor off, after them back I now have a low pressure problem. There are no apparent leaks from the pump and the one O ring seems to be in proper placement.
 Reply

InyoPools Product Specialist  Posted: 10/11/2016 

Art - Do you notice a significant reduction in water flow? For example, is your cleaner still operating? If flow is still good, your pressure gauge may be failing. If your water flow is down, check for a clogged impeller.
 Reply

 Posted: 10/5/2016 

My pool pressure historically (7 years)without the solar system on was 20, with the system operating it increases to 28. I recently had the 4 cartridge filters cleaned and the solar system was serviced and shut off for the winter. The pressure immediately settled to 10. Are there any special things that would account for this change? I will proceed with the recommendations noted on this site checking the skimmers, pump basket and pump lid seal etc. Thanks.
 Reply

InyoPools Product Specialist  Posted: 8/23/2016 

Big al - This sounds like an air leak causing back pressure to build up in the top of the filter tank. When you press down on the valve handle, you may be releasing that backpressure. But that is inconsistent with your filter gauge losing pressure (I assume as seen at the filter gauge). Backpressure should cause the gauge reading to increase. Check your pump's propeller to see if it is clogged. That is a common problem that leads to low pressure.
 Reply

 Posted: 8/23/2016 

My earth pool filter loses pressure. I will stop the pump then pump the handle several tiles and it works fine then within the hour the pressure reduces dramatically. So i stop filter and pump again. Repeating the process several times. What is the problem?
 Reply

InyoPools Product Specialist  Posted: 8/1/2016 

Steve - Try applying a soapy solution around all the pipe connections in the suction line(s) between the pool and the pump. Turn the pump on. If you have a leak in any of the connections, you will see the soap bubbles moving as they are sucked into the air leak. Don't forget to check the isolation valve.
 Reply

 Posted: 7/29/2016 

I repeatedly lose jet pressure. I turn off pump, sometimes open the pump strainer lid after shutting off isolation valve, release air pressure from air relief valve, start the motor again, close the air relief and have opened the isolation valve to the pump. This corrects the problem for about 10 minutes, then the pressure from jet drops by about half, another hour and pressure has dropped again until after 24 hours, there is barely a trickle coming from the jet. I repeat the process and the same thing happens again, again, and again . Very frustrating!!!! After readin your article, my only guess (the pool is only 6 weeks old and doubt there's any blockage) is that the piping from the skimmer to the pump has a tiny air leak. sometimes after just shutting pump off for a minute, it corrects until I need to shut it off again for another minute after pressure drops once more. HELP!
 Reply

InyoPools Product Specialist  Posted: 7/21/2016 

bpic - You don't need a larger pump. If you are getting that much debris in your filter system, I would look at getting a larger filter like the Star Clear Plus 120 Sq Ft. Filter 1.5" Ports. Also, you probably need a larger filter to handle the GPM of the 1.5 HP pump. And if you are getting that much debris into your filter, check your pump impeller periodically to see if it is clogged. See our guide on "How To Clean Out a Pool Pump Impeller".
 Reply

 Posted: 7/17/2016 

My filter unti recently cracked down the side and needed to be replaced. It was a two filter unit. When i replaced it, the guy at the store asked how many gallons my pool held. I told him it was a small 10k gallon pool. He said the two filter unit was way too big and sold me a one- filter unit for about half the price of the 2 filter unit. When i hooked it up, it ran great for a few hours, then i noticed that the water wasnt circulating and nothing was coming out of the jets. I cleaned the filter and it ran great again...for a few hours...then the same problem. The filtert clogs and the system stops moving water about 45 minutes after each cleaning. The one-filter unit i bought (Hayward C751 Star-Clear Plus)says its rated for up to 36k gallon pools. Mine is much smaller. Someone told me my filter clogs quickly because im on a lake and i need to go back to the two filter system. Others have told me that my pump motor may be too small (1.5 hp). At this point, im not sure if i need to buy a bigger pump motor or take out the new filter unit and put a 2 filter unit back in. Any thoughts? Thanks.
 Reply

InyoPools Product Specialist  Posted: 7/12/2016 

Casey in Missouri - It sounds like you may have a damaged spider gasket. See our guide on "How to Replace a Spider Gasket on a Multiport Valve" for information on how to access and possibly replace the spider gasket. Remember to shut off the pump before changing valve settings.
 Reply

 Posted: 7/10/2016 

I replaced the multi port valve on top of my Tagelus sand filter and replumbed everything above ground about a month ago. It was filtering fine and washing fine. Everything fine. I just vacuumed (to waste) and when I turned it back to filter, it won't create enough suction to stay up with the pump. The weird thing is, that it works fine when I open the drain (suction) valve. Also, every time I backwash and rinse, I still get sand/green put back into the returns.

-confused Casey
 Reply

InyoPools Product Specialist  Posted: 7/6/2016 

gary bunn - If you are vacuuming significant algae from your pool and your MPV is set at Filter, you may have saturated your filter. Try backwashing and Rinsing your filter 2-3 times to clear the algae. If your MPV is set to Waste and you are getting water/algae back into the return line, you may have a damaged spider valve in the MPV. See our guide on "How to Replace a Spider Gasket on a Multiport Valve".
 Reply

 Posted: 7/6/2016 

Thanks very much for some very good tips.
 Reply

 Posted: 7/3/2016 

I have a new two speed pump and sand filter from Inyo. When I vacuum I can see the the alge returning to the pool from the return line. Does anyone have advise on this?
 Reply

InyoPools Product Specialist  Posted: 6/28/2016 

larends - If get strong water flow when you bypass the filter (by putting it is recirculate mode if you have a MPV), then your low water flow problem would be in the filter. If you have a sand filter and haven't change the sand in the last 5 years, try that now. If you have a cartridge filter, buy a new cartridge. The cartridge may look clean, but may be clogged with oils and chemical that are difficult to wash out.
 Reply

 Posted: 6/27/2016 

My water is coming out of the jets slow unless I by pass to pool I have checked the filter and the pump components and they are clear.. could this indicate a problem in the filer.. It is super fast and a powerful force when I by pass the filter.
 Reply

InyoPools Product Specialist  Posted: 6/22/2016 

Lupe - This one has me stumped, especially since you are basically using new equipment int your filter. Is it possible that the "Flex Air Relief Assembly" is getting clogged? See number #15 in this "Hayward Pro Grid Perm-A-Glass DE parts list". When you find the solution to this problem, would you let me know. Thanks.
 Reply

InyoPools Product Specialist  Posted: 6/21/2016 

Nik - Clogged baskets are probably the most common followed by a clogged impeller.
 Reply

 Posted: 6/20/2016 

Awesome post! very helpful and detailed. Would like to know, which of those are occurs the most common? thanks for sharing!
 Reply

 Posted: 6/18/2016 

I'm having the same issues with low to no water pressure. I have a Hayward DE 4820 Filter, a Hayward SP0710XR50 Vari-Flo Backwash, and Hayward CL200 Chlorinator. About a month ago, I noticed my water flow decrease to a standstill. A neighbor behind me has a huge pine needle tree that loves to feed my pump. I began to work the problem starting with routine check of my pump, remove debris from impeller as with replace all seals and O-rings..resulting in no change. Multiple backwashes results in about a few minutes of strong water flow followed by an increase in psi. I also checked for leaks, blockages in the water line, nothing found. Here's the kicker, when I remove my whole filter assembly (manifolds + grids), my system will runs for days with absolutely no increase in psi or change in water flow. Okay, so it my filter assembly? I went ahead and purchased new grids and manifold (w/ air release) hoping this would solve my issue. To my frustration, after inserting my new filter grid assembly and applying lube where needed, my pressure in about ten minutes went from 10psi to 25psi. I removed the new grid assembly from the filter and ran it bare with absolutely no issues. I presently have a green pond and only able to circulate green murky water. Any thoughts on why when filter grids are used that I lose water pressure, and when running bare there are no issues?
 Reply

InyoPools Product Specialist  Posted: 6/17/2016 

Swagg88 - See if you can isolate the problem to the filter. If you have a cartridge filter, try running without the cartridge. If you have a sand or DE filter, put the MPV in Recirculate to bypass the filter. If either of these works, look at replacing the cartridge or sand/DE. For the sand filter, check the laterals, lateral hub, and standpipe for cracks. For DE check for too much DE on the grids and check for breaks in the upper and lower manifolds.
 Reply

 Posted: 6/14/2016 

Hi, I have tried all of these things on this site. My pool was working just fine, then turned the pump off for a day... After that no suction. Pool guy came and found nothing wrong, replaced all seals anyway. He said we may have a underground obstruction. I got a bladder which I inserted, water flowed freely. Pump had so much suction it was pulling our thermometer and chlorine dispenser into skimmer! Turned off to clean debris from bottom drain, off maybe 4 hours. No suction, nothing. Motor is running, cleaned everything including impeller. Tried the bladder again, water seems to be flowing freely. Cannot prime, no suction, no visible leak, no water loss. Any ideas?
 Reply

 Posted: 6/14/2016 

Thanks for the article! Have had low pressure for a few days, went out and noticed a small bit of water dripping from basket filter lid after I turned off the system. Turned out my gasket was mangled!
 Reply

InyoPools Product Specialist  Posted: 6/8/2016 

Proline 75 DE filter - First, Try running with a little less DE power. If that doesn't work, and you have had your grids awhile, it may be time to change them. Oils and chemicals build up in the fabrics that are difficult to clean out.
 Reply

InyoPools Product Specialist  Posted: 6/8/2016 

Emerson56 - If you have diverter valves, try shutting down part of the flow from the main drain to divert more suction to the skimmer. If that doesn't work, you may have a partial blockage in the skimmer suction pipe. Have someone blow out that pipe for you.
 Reply

InyoPools Product Specialist  Posted: 6/8/2016 

rrtresp28 - One customer had a very similar problem. Flow would stop in 15 minutes. Worked again after backwash but stopped again after 15 minutes. He found that his internal filter piping had a crack in the hub that the laterals connected to. Crack was letting sand into the laterals and clogging them. Backwash temporarily cleared them. Filter mode clogged them up again. You might have to pull out your sand again and check the standpipe, hub and laterals for cracks. Note: Before you pull out he sand, try running the system in recirculate mode. If an internal crack is the problem, system should flow well in recirculate mode which bypasses the filter.
 Reply

Anonymous  Posted: 6/7/2016 

I just bought a proline 75 DE filter. Preasure is good to start then within a hour there is no preasure. Put in 2 1/2 lbs of earth as the instructions said. What am I doing wrong?
 Reply

 Posted: 6/7/2016 

Just had my pool service and assured all is functioning properly. My problem has been and Continental to be a build up of surface bugs and small debris. I disconnect the pool vaccine and have the filter run with all actions going to the skimmer. As I sit and watch the flow in the skimmer I see 90% of small surface bugs/material passing by the skimmer. 10% I can see being drawn by the vaccine of the filter. Filter is new as is the pressure valve that is reading 12 psi. Filter is running 10 hours a day. We never seem to clean the surfsce. Do I have a problem or am I expecting too much from the system? Thanks for your help
 Reply

InyoPools Product Specialist  Posted: 6/7/2016 

DE4800 - The flex air relief assembly would be a good place to start. If it is clogged, it may be allowing air pressure to build up in the top of the tank and causing backpressure. If you have had your grids for a while, they may be clogged with oils and chemicals that are difficult to wash out. Try replacing every other one and see if that helps.
 Reply