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.

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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".

Comments

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(1 to 40 of 213)

Inyopools  Posted: 06/24/2017 12:37 PM  Latest 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  Latest

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  Latest 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".


Bama Bill  Posted: 06/02/2017 16:52 PM 

Hello,

I have a Hayward C900. I am not getting enough flow streaming to the pool.
When I REMOVE the filter (PA90), the flow is greater and the pool cleaner (Zodiac) works perfectly. Once I put back in the filter, the flow coming out is very slow. It is a 30-day old, clean filter. The flow is ok but not strong enough to get the Zodiac suction going to clean the pool.

Do you have any suggestions, please?


Inyopools  Posted: 06/02/2017 12:54 PM  Inyo Product Specialist

The Judge - Sounds like you have a clog in the pipe going to your second jet. Try blowing the pipe from the return with a Drain King attached to a garden hose. Or, if you can open up the system at the pump or filter and try blowing the clog out forward to the pool. When you do the second option, you will need to buy a plug for the jet that works.


Inyopools  Posted: 06/02/2017 10:17 AM  Inyo Product Specialist

InCanada - First check that the impeller in your pump is not clogged. Then check for backpressure in your filter tank. When you shut down your pump, do you have a reverse surge of water through your pump back to the skimmer? If so, you have air pressure building up in the top of your filter tank that is causing backpressure against the incoming water. This is caused by a suction air leak between the suction side of your pump and the skimmer. To correct this, see our guide on "How to Identify and Correct Air Leaks".


Barbara  Posted: 06/01/2017 21:01 PM 

I opened my pool and the filter was running fine except I don't think it was filtering at its best. I changed the cartridge in my filter. Now I can't get a prime. It runs and runs and there's water in the pump but no outflow. Can anyone help?


The Judge  Posted: 06/01/2017 10:36 AM 

In-ground pool- One return Jet working fine, the other wont shoot any water. Filter gauge pressure is high. Tried covering the working Jet up but it didn't get the other Jet going. Any suggestions?


InCanada  Posted: 05/31/2017 11:17 AM 

Pool pump works great when first plugged in. But after about 10 minutes, the water flow into the pool drops to about half of what it was. We have checked and tightened all fittings. No leaks that we can find. Filter clean and skimmer basket are both clean. Any suggestions of what is causing our problem?


Inyopools  Posted: 05/29/2017 22:53 PM  Inyo Product Specialist

happyal - I don't know the term "carriers" but your low overflow may be due to low water pressure. See Steps 6 and 7 of this guide. A clogged impeller and suction leaks are common causes.


happyal  Posted: 05/28/2017 7:40 AM 

I'm not getting much over Flo from my spa into the pool. Only time I get good over Flo is when I clean my carriers. What could be the problem?


Inyopools  Posted: 05/26/2017 18:18 PM  Inyo Product Specialist

Myles g - Check to see if your motor's impeller is clogged. This is a very common problem for low water pressure which leads to poor filtration. See our guide on "How To Clean Out a Pool Pump Impeller".


Myles g  Posted: 05/26/2017 9:58 AM 

I have my filters working I believe I have a gauge problem but my pool is staying cloudy my sweeper is not working so great I know that can cause it but I honestly think the water is just passing through filter without actually getting filtered. Is there something I can do


MasterInspector  Posted: 05/24/2017 21:32 PM 

An excellent article. As an SFR/MFR inspector who also inspects pools, I see a lot of faulty 'weirs' that are either stuck, missing or are damaged, which causes problems or compounds other problems. And to be honest...I see a lot of pools without a 'weir' that seem to be working just fine while I'm there...but each component in an engineered pool system has a job to do and any one part or combination of parts that don't function as designed can be problematic and should be addressed. So...don't overlook the 'weir' when performing system troubleshooting and analysis.


Inyopools  Posted: 05/22/2017 12:37 PM  Inyo Product Specialist

K - This sounds like you have an above ground pool (short hoses) and that you've covered any possible air suction leaks. Sometimes you can't get to the stubborn impeller clogs with a hanger. You may have to take the motor out of the pump housing to get a better look at the impeller slots. See the first part of our guide on "How To Replace A Pool Pump Impeller" for information on getting to the impeller.


Inyopools  Posted: 05/19/2017 13:01 PM  Inyo Product Specialist

Tyger - If you have great flow from the spa intakes, it sounds like you may have a blockage in the line between the spa/pool diverter valve and the skimmer/main drain valve. I assume that there is no difference in flow if you alternately shut off the skimmer or main drain. Take the tops off the two valves and try pushing a plumbers wire between the valves.


K  Posted: 05/19/2017 10:53 AM 

Hi- Hayward sand filter 7-8 years old that wont stay primed- o ring changed with silicone lube.all hoses on suction side redone, and impeller cleared with coat hanger per your how to video- still no dice- pump sounds fine- but loses prime & pressure- thoughts?


Tyger  Posted: 05/18/2017 13:24 PM 

Can't figure out why my pool has such weak return flow after its been running for a few minutes, but when it's filtering the spa the return is great. When I backwash it has great return, but then shortly after its weak again.


Tyger  Posted: 05/18/2017 13:17 PM 

Can't figure out why my pool has such weak return flow after its been running for a few minutes, but when it's filtering the spa the return is great. When I backwash it has great return, but then shortly after its weak again.


Inyopools  Posted: 05/18/2017 10:35 AM  Inyo Product Specialist

Paula - You may have a clogged or damaged impeller. I would pull the motor out and check the impeller for damage or to see if small rocks have wedged themselves inside the impeller blocking flow. Also, check for damage to the diffuser.


Paula  Posted: 05/17/2017 10:46 AM 

We recently had concrete deck around pool redone. NO filtration problems before renovation. They repaired a pipe from skimmer to pump after priming failure (leak) with four 90s. Pool began algae issues - chemistry good. Made contractor remove four 90s with just an additional 45, etc. Bubbles in pump basket immediately - not enough to prevent priming (priming now takes 30 sec). Still have eventual issues with algae which I'm attributing to not enough flow. Impeller can be moved freely with screwdriver - but does this "movement" clear it of blockage or must we examine it? This contractor did not cover pool, said easier to pick out the big pieces of concrete, than vacuumed. Could smaller concrete pieces be clogging the main drain or skimmer piping? Enough to create small air bubbles? The pipe crack was easily found with water on surface. Can smaller cracks not show water above? Contractor says working good, but I know my pool. Somethings different causing eventual algae at tile line.
Thanks


Inyopools  Posted: 05/15/2017 15:02 PM  Inyo Product Specialist

james - I assume you changed the impeller. Did you match the new impeller by part number off the old one? With the way motors are labeled, uprated and full rated, it is easy to get the wrong impeller. Did the loose blade damage the diffuser. Ensure that the impeller is not clogged.


james  Posted: 05/15/2017 13:23 PM 

I recently had a lot of issues with my pool and came to find out one of my issues was a blade in my impeller broke off and had blocked it from working correctly, fixed that and also replaced all my grids on my DE filter since some were old & torn and letting DE escape into my pool. After all that, it took me a while to get my pump to prime (it finally primed after I let it backwash for a few minutes). Got it working and all seemed good, even my Kreepy was working great. Then after a few days, my pressure went to zero, my Kreepy quit working and noticed one of my return jets had bubbles coming out of it meaning I was getting air somewhere. I checked all my piping and can not see any place where I might be getting air into the system. My water seems to be circulating fine in the pool, just have the low pressure and no kreepy. Anything else I might have missed?


Inyopools  Posted: 05/06/2017 12:21 PM  Inyo Product Specialist

Anonymous (pump damage) - Your pump is probably all right if it's still running. I'd check for other low-pressure issues like a clogged impeller or suction side air leaks.


Anonymous  Posted: 05/04/2017 20:52 PM 

I accidentally left my pump on for about a week with the return valves shut off. Now my water pressure seems low. Could I have damaged my pump?

Any help would be appreciated!


Inyopools  Posted: 05/01/2017 12:43 PM  Inyo Product Specialist

Mike - If I understand what you wrote, when you take the Multiport valve out of the system piping, you get water pressure in at the filter pressure relief valve and water flows through the system. If this is so, you have a problem with your MPV. Check to see if the spider gasket in the MPV is damaged or if there is something in the valve that is blocking water flow. If this is a new installation, make sure you have installed the MPV correctly.


Mike  Posted: 04/28/2017 8:52 AM 

Hi I am having a problem with my in ground pool ihave no pressure gauge is showing zero and no water in skimmer on pump did a few things I have sand filter I took the valve assembly of the filter housing and started up pump then I got water pressure,and water in skimmer with the valve of could you give me advise of what it could be thanks


Inyopools  Posted: 04/19/2017 9:58 AM  Inyo Product Specialist

Mike - You may have a leak in the cleaner hose that lays on top of the water. Try holding the hose below the top of the water to see if that solves your problem. If it is the hose, remove a section of the hose one at a time until you find the one that leaks.


Mike  Posted: 04/18/2017 6:19 AM 

When running my pool cleaner the pressure seems to disappear after about 2minutes and the cleaner stops. I then disconnect the cleaner and after the pump has run for a period again air comes out of the water flow pipe in large bubbles. I have added some solar panels to heat the pool in winter.
Please help .


Val Williams  Posted: 03/24/2017 13:00 PM 

What a HUGE help this article was. I had done everything BUT check to see if the impeller was clogged. Had my problem fixed in 5 minutes. THANK YOU!