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

First, a short discussion on how a pool system works. The piping in a pool has two sides: the suction side that is before the pump and a pressure side that is after the pump. The pump creates a vacuum that sucks water from the pool and then pushes it back into the pool through a filter. A leak in the suction side will cause air to be sucked into the system. A leak on the pressure side will cause water to spray. If you have a blockage in the suction side of the pump, the blockage will restrict the amount of water to the pump that will result in low pressure. A blockage in the pressure side, like a dirty filter, will have the opposite effect and will cause the pressure to go up. Here are the common causes for low pressure - the easiest to fix is explained first.

Step 2

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

Step 3

CLOGGED SKIMMER BASKET (Low PSI) - If your skimmer basket is full of debris, you are effectively shutting off the pipe between the skimmer and the pump. Generally, this will reduce the flow of water to the pump. If the pump has less water entering it, it is moving less water out. This means the pump is doing less work that in turn will reduce water pressure.

Solution: Clean your skimmer basket by removing any debris.

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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(1 to 40 of 361)

 Posted: 7/19/2021 

After I do a backwash jets are working perfect. As the day progress pressure gets weaker and weaker. Then I do a quick backwash and good again.. However having to do this on the daily. What is causing this?
 Reply

InyoPools Product Specialist  Posted: 7/20/2021 

That is covered in the guide, step 5: chemically soak your cartridges or grids
 Reply

 Posted: 7/14/2021 

we just replaced our de to a sand filter, replaced the motor with a two cycle one, new vacuum hayward with the two wheels. All at te recommendation of our new pool service. Drained the pool, scrubbed the sides and still not enough pressure to move water or vac. Keep on telling my pool guy we don';t have enough pressure. what can I do? is it the new motor?
 Reply

InyoPools Product Specialist  Posted: 8/4/2021  Latest

Since it is dual speed motor, are you running it at high or low speed? Most dual-speed motors are scheduled to run at low speed mostly. If you want to vacuum, you must manually change the speed to high RPMs at the timer or switch.
 Reply

 Posted: 6/15/2021 

Can a pump be moving water but still have low pressure? My gauge is showing zero but I have circulating water. Also, the heater is showing flow error..
 Reply

InyoPools Product Specialist  Posted: 6/17/2021 

If the pump is moving water, the system should show some pressure reading. Have you tried cleaning the filter?
 Reply

 Posted: 6/3/2021 

Just replaced our Hayward S220t sand filter. It seems to run fine when first started but over a few hours the PSI increases and flow decreases. The heat pump flashes no flow and no flow will eventually illuminate on AquaRite. The water is always clean during the backwashes. We are also picking up sand in the pool cleaner. Everything else seems to be functioning normally. Any suggestions?
 Reply

InyoPools Product Specialist  Posted: 6/4/2021 

Did you replace the sand filter with the same fixed filter tank? If it was a smaller-sized filter, it would explain the excessive clean cycles. Is your water clear or are you dealing with cloudy or green water?
 Reply

 Posted: 6/2/2021 

Will a leak in my return pipes (after filter) cause low pressure?
 Reply

InyoPools Product Specialist  Posted: 6/4/2021 

I guess it would depend on how big the leak is; is it pouring or dropping? Either way, a leak isn't good and it should be sealed up. But chances are the leak isn't big enough to cause a drop in pressure.
 Reply

 Posted: 5/13/2021 

Getting a low flow error from Hayward heater, I noticed the pressure in my filter was high as well, so I removed filters and chemically cleaned. Reinstalled and everything worked fine for 24 hours, then same error. I removed the filters and ran system without filter media, no error from heater. My filters are only 2 years old and in good condition but my pump is 10 years old, Hayward tristar sp32005ee. Good my pump be bad how can I test my pump?
 Reply

InyoPools Product Specialist  Posted: 5/14/2021 

It is not your pump it is your cartridges. The system slows down after 24 hours use post an acid soak, and the pump runs fine with the cartridges taken out. The problem is the cartridges unless you are already dealing with green or cloudy water that is clogging the cartridges quicker than normal. If it was the pump, your system wouldn't be working with the cartridges taken out.Old cartridges can be soaked, look clean, and still be chocked full of years of debris. This is why eventually chemical soaks are no longer effective and you just have to get new cartridges.
 Reply

Anonymous  Posted: 5/14/2021 

Thx Matt, my plan was to trying to locate replacement filters today and test that theory as that is what I was leaning towards too.
 Reply

 Posted: 4/27/2021 

We just opened the above ground pool and after a couple of hrs of filtering the pool loose pressure and after back wash it works right for a couple more hrs do anyone have any ideas whats happening
 Reply

InyoPools Product Specialist  Posted: 5/13/2021 

Is your water clear, cloudy or green? If it is the latter two, you are having pressure issues because whatever is making your water murky is clogging the filter quickly after you clean it. Guides that might help: How To Go From Cloudy To A Crystal Clear Pool & How to Clean a Green Pool?
 Reply

 Posted: 4/14/2021 

I have a separate pump for a waterfall and after it runs for about an hour the water flow reduces to a very slow trickle of water. Why does the water stop flowing after an hour running?
 Reply

InyoPools Product Specialist  Posted: 4/16/2021 

It could be any of the things we show in this guide, besides the filter if it is a standalone pump setup. Have you done any troubleshooting we mention above? That'd at least narrow down the field of possibilities for us to consider.
 Reply

 Posted: 4/9/2021 

I have a salt water heated pool and the Raypac heater keeps shutting off and restarting .The error code is HP6 . Filter and skimmer were just cleaned .PSI on the filter is 20 .
 Reply

InyoPools Product Specialist  Posted: 4/16/2021 

This was listed in the manual concerning the HP6 code: "Low water flow in the unit or faulty high-pressure control. Check water flow/backwash. The unit will show (HP6) after 6 HP faults. This will stop the unit for protection."What is the model number of your pool heater? I can try to find a replacement high pressure control.
 Reply

 Posted: 4/16/2021 

Its a RAYPAK R8350TI-E
 Reply

InyoPools Product Specialist  Posted: 4/21/2021 

You have a high-pressure fault. This is the part, we currently do not stock it, though High Pressure Control kit H000015
 Reply

 Posted: 3/23/2021 

I have DE filter 24 ft² . I just had the gaskets replaced to my pump. I keep losing prime in my pump after an hour or 2 of running the pressure gets up to 30 in my filter. Filters are brand new less then a month old .
 Reply

InyoPools Product Specialist  Posted: 3/23/2021 

There are quite a few things mentioned in the guide to check besides the pump gaskets. Did you check the water level, valves, unions, and plumbing joints for sucking air leaks? Another helpful guide you should read: How to Find Suction Side Air Leaks In A Pool
 Reply

 Posted: 8/17/2020 

I have pressure when backwashing, rinsing.... but jets have very low pressure. Have cleaned cell, emptied skimmers and pump basket. Any other tricks???
 Reply

InyoPools Product Specialist  Posted: 8/24/2020 

What type of filter do you have? Is it Sand or DE? if it is sand, how old is the sand? Old sand can reduce your system's pressure even after thorough backwashing.Another thing to try is to set the filter to "recirculate' to bypass the filter media to determine if the filter media is the issue or if you should be looking elsewhere.
 Reply

 Posted: 7/29/2020 

Hi, I Noticed my jet return is very weak. I have a DE filter and after I backwashes, the return is good for about 15 minutes then weak again. I cleaned the skimmer and pump baskets .And I fixed my water level as well. Any other ideas?
 Reply

InyoPools Product Specialist  Posted: 9/8/2020 

What is the model number of your filter, and how much DE are you adding after a backwash?
 Reply

 Posted: 7/22/2020 

Skimmer was replaced and a "rubber boot" was used to connect the pipes. Now the PSI is low and the pump will not hold prime. Could the connection have collapsed to cause this?
 Reply

InyoPools Product Specialist  Posted: 8/26/2020 

The rubber boot could be collapsing, which restricts the flow of the pump. Or, the boot may be watertight but not airtight. So when the pump is pulling in water, it is creating a vacuum that may compromise the seal around the boot. If the boot is on the suction-side, water won't leak out, but air can be pulled in, which will cause the pump to lose prime. I'd replace that boot with a proper glued PVC joint
 Reply

 Posted: 7/5/2020 

Hi. I have little pressure coming out of my 3 jets. I cleaned the cartridges, made sure nothing was clogged (all the baskets are empty, even the motor basket). Could it be my cartridges need replacing. I do have them for 14 yrs. Thank you.
 Reply

InyoPools Product Specialist  Posted: 10/20/2020 

There is a definite possibility the issue is due to old cartridges. I suggest giving them a chemical soak, and if that doesn't work, it is time to replace them.
 Reply

 Posted: 6/20/2020 

I have a DE filter and psi is at 6. I have cloudy blue water. Can low psi be the reason? BTW, I'm a first time pool owner
 Reply

InyoPools Product Specialist  Posted: 9/2/2020 

What is your usual psi reading? Do you have a dual or variable speed pump?Cloudy blue water could be down to a bad combination of chemicals being added at the same time or it could be algae. I would consider using a clarifier or a flocculant.
 Reply

 Posted: 5/28/2020 

The problem we are having is when we shut off the pump we hear water draining the pressure gauge goes up then shuts down what is the problem
 Reply

InyoPools Product Specialist  Posted: 10/27/2020 

You likely have an air leak which is causing your pump to lose prime. I would read this guide to determine where it is and how to fix it: How to Identify and Correct Air Leaks
 Reply

Anonymous  Posted: 4/19/2020 

Just drained and refilled my pool, new pump, new sand. Everything is good to go while the pump runs on high, when it runs on low, we have no pressure. Any ideas???
 Reply

InyoPools Product Specialist  Posted: 4/24/2020 

Does the pump lose prime or does the pressure just dip? Low speed usually sees your flow rate take a dive, but that is to be expected.
 Reply

 Posted: 4/11/2020 

I just shocked my pool had it for 3 years now. Once i run filter the pressure gauge goes up to 22 and the water in pool is real weak. I backwashed the sand filter and when i turn it back on everything works fine for about 20 min pressure goes back up and output water in pool is weak again. No lights are flashing on panel. If i run on recirculation it flows perfect with power. I’m wondering is it’s a problem with the sand, or pressure gauge. I have correct amount of water level in pool. I checked for leaks. I have no clogged baskets or clogged pipes ( unless it’s clogged in the filter system) i wanted to see was this normal and would get better over time since i shocked it or i have a bigger problem within the sand filter system.
 Reply

InyoPools Product Specialist  Posted: 4/17/2020 

Filter sand will eventually get so dirty that even a thorough backwash will not prevent pressure spikes. Filter sand has an expected life of 3-5 years before it needs to be changed. Since you are in that window, I'd say it is time to make a run to the local hardware store for some #20 silica.The water pressure issue subsiding when you bypass the filter media is a big sign that the sand is bad.
 Reply

 Posted: 4/4/2020 

I cannot get water flow to my Pentair 300 chloinator. No air bubbles anywhere. Just cleaned filter. I can get water to shoot into chlorinator by switching input valva back and forth between spa and pool but nothing will get it flowing. I also have no outflow on one jet in spa. What can I try?
 Reply