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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 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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(161 to 200 of 373)

InyoPools Product Specialist Dennis R. Posted: 6/24/2017

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.
Reply

Anonymous Posted: 6/22/2017

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?
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InyoPools Product Specialist Dennis R. Posted: 6/20/2017

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.
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InyoPools Product Specialist Dennis R. Posted: 6/19/2017

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.
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Val Posted: 6/19/2017

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.
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Sherri Posted: 6/18/2017

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
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InyoPools Product Specialist Dennis R. Posted: 6/11/2017

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.
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inultus Posted: 6/10/2017

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.
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InyoPools Product Specialist Dennis R. Posted: 6/8/2017

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?
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DMS Posted: 6/6/2017

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?
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InyoPools Product Specialist Dennis R. Posted: 6/4/2017

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.
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Anonymous Posted: 6/4/2017

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....
Reply

InyoPools Product Specialist Dennis R. Posted: 6/4/2017

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".
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Bama Bill Posted: 6/2/2017

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?
Reply

InyoPools Product Specialist Dennis R. Posted: 6/2/2017

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.
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InyoPools Product Specialist Dennis R. Posted: 6/2/2017

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".
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Barbara Posted: 6/1/2017

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?
Reply

The Judge Posted: 6/1/2017

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?
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InCanada Posted: 5/31/2017

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?
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InyoPools Product Specialist Dennis R. Posted: 5/29/2017

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.
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happyal Posted: 5/28/2017

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?
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InyoPools Product Specialist Dennis R. Posted: 5/26/2017

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".
Reply

Myles g Posted: 5/26/2017

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
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MasterInspector Posted: 5/24/2017

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.
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InyoPools Product Specialist Dennis R. Posted: 5/22/2017

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.
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InyoPools Product Specialist Dennis R. Posted: 5/19/2017

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.
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K Posted: 5/19/2017

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?
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Tyger Posted: 5/18/2017

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.
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Tyger Posted: 5/18/2017

InyoPools Product Specialist Dennis R. Posted: 5/18/2017

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.
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Paula Posted: 5/17/2017

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
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InyoPools Product Specialist Dennis R. Posted: 5/15/2017

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.
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james Posted: 5/15/2017

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?
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InyoPools Product Specialist Dennis R. Posted: 5/6/2017

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.
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Anonymous Posted: 5/4/2017

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!
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InyoPools Product Specialist Dennis R. Posted: 5/1/2017

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.
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Mike Posted: 4/28/2017

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
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InyoPools Product Specialist Dennis R. Posted: 4/19/2017

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.
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Mike Posted: 4/18/2017

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 .
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Val Williams Posted: 3/24/2017

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!
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