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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(41 to 80 of 373)

InyoPools Product Specialist Matt S. 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

Vickie 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 Matt S. 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.
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Mike 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
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InyoPools Product Specialist Matt S. 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

Danielle Gross 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
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InyoPools Product Specialist Matt S. 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
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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???
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InyoPools Product Specialist Matt S. 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.
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Montez Matt 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 Matt S. 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

Rudy Mayer 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

InyoPools Product Specialist Matt S. Posted: 4/7/2020

Have you made sure the feeder lines are clear and not pinched or damaged in any way?
Reply

renzo Posted: 1/6/2020

Hi this is not normal my pool it is running normal but when i run the manual vacuum after a few minutes the suction slow ver low and partially stop sucking and if i disconnect the hose after a few minutes the pressure starts again to normal
Reply

InyoPools Product Specialist Robert M. Posted: 1/6/2020

Hello Renzo - First, make sure all the air is blown out of the vac hose before plugging it into the skimmer. Check for any holes in the vac hose and replace it if there are holes. If air is not the issue, you may have a problem with the pump not receiving enough water. If you have a main drain, slightly open that line so that the pump can get more water.
Reply

DHO Posted: 12/22/2019

After a wind storm the pump pressure dropped to near zero. Following your recommendation I used a coat hanger wire as a way to clear the pump's intake of debris. Reassembled, and started the pump, success! About a week later, no pressure. Redid the use of the hanger but before reassembling I carefully checked the strainer basket. A seam was cracked from top to bottom letting any debris into the pump. It is now replaced.
Reply

InyoPools Product Specialist Matt S. Posted: 12/26/2019

Good troubleshooting!
Reply

Shaun Posted: 12/22/2019

Hi, I have replaced the sand in my pool filter with a sponge medium. When I run the pump on filter it has low suction, but if I "block" the hose on the cleaner with my hand the suction builds up and is very strong, but as soon as I let go it gets weak very quickly. We had just taken the medium out, cleaned it, and returned it before this problem started. What advise could you give me?
Reply

InyoPools Product Specialist Matt S. Posted: 12/26/2019

Have you checked that the hose does not have pinhole air leaks? If the problem only subsides when you take the hose out of the equation, then I would say it is a problem. You may want to check that your impeller or pump basket is not clogged. Those two factors could cause your pump's suction to be reduced, making the extra "head" of the cleaner hose is too much.
Reply

Gayetta Johnso Posted: 6/28/2019

Thank you, I am a 65 year old female from Wyoming. My pool company Watco at Billings went under last year it's really hard to get help here!
Reply

Carl Posted: 5/29/2019

I have a Clearwater II cartridge system. Low inlet and out let pressure. Above normal pressure in cartridge tank. Cartridge less than 1 week old. Used plumbing snake on suction and outlet side. No obstruction. Any suggestions
Reply

InyoPools Product Specialist Matt S. Posted: 5/30/2019

Are you sure you purchased the correct cartridge size? Some models have cartridges with the same overall dimensions but different square footage and flow ratings. If you bought a smaller cartridge, the flow would be restricted as you explained.
Reply

robert f farrell jr Posted: 5/23/2019

I have a DE filter, cleaned it a few times. If I put it on recirculating or backwash I have plenty of pressure. Run it on filter starts strong and pressure does out in a few minutes.
Reply

InyoPools Product Specialist Matt S. Posted: 5/24/2019

Give your grids a chemical soak to clean out the nooks and crannies of the material. Even though the DE powder does most of the filtering, the grid material can get caked with dirt and muck too.
Reply

John Posted: 5/22/2019

Looking for advice on low flow only when on filter. Flow is great on drain and backwash, but low on filter (even the clear vessel barely fills up one third). I have backwashed for several minutes still without luck. Obviously the pump is working given the strong flow on drain. Would I have a blockage out back towards the pool?...need to replace the sand? How can I test and eliminate? Thanks in advance.
Reply

InyoPools Product Specialist Matt S. Posted: 5/23/2019

How old is the sand?
Reply

John Posted: 5/23/2019

Found out this morning that the sand hasn't been replaced - approx 8 years old. Live in Canada so only getting 3 months use (at the most) and from what I understand from previous owner, have never had any issues last summer. I guess I should first check the filter handle mechanism for damage and then replace the sand?
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InyoPools Product Specialist Robert M. Posted: 5/23/2019

It seems like the valve is working correctly. If you backwash and there is no change in the flow in filter mode, it's time to change the sand.
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Mary Posted: 5/18/2019

I had a Jandy Stealth pump that was just replaced early fall last year, and given a Jandy VS FloPro. It now warmer out and algae growing. Variable speed pump is not making the rest of the unground cleaning heads pop up. Do you think the pump has anything to do with the pool not getting clean? Every few days I have to shock the pool.
Reply

InyoPools Product Specialist Matt S. Posted: 5/20/2019

Have you increased the run speed and time of the pump? The variable schedule may be set at a run time that is ok for the cooler months but not suited for the algae bloom season.
Reply

Rumit Posted: 5/17/2019

The water flow in my pool goes low after a few hours. To resolve it I backwash, and the flow is fast & efficnet. But then again after a few hours there is barely any flow.
Reply

InyoPools Product Specialist Matt S. Posted: 5/20/2019

Is your pool green or cloudy? If this is a sand filter when was the last time you changed the sand?
Reply

Rumit Posted: 5/20/2019

The water is blue and clear. The pump ocassionally times out because of a priming error (not enough water filling into the strainer pot). The skimmer basket is free of debris, the strainer basket is also free of debris, the impeller seems to work fine, water flows out of the returns. The filter is a DE filter. It has a reading of about 18 psi. Also, the backwash flow is normal. I’ve released air from the knob at the top of the DE filter. The restricted water intake from the main skimmer line results in the Inteliflo chlorinater reading a no flow error. The skimmer basket initially has good flow after a backwash but then return soon to having low flow and priming error.
Reply

InyoPools Product Specialist Matt S. Posted: 5/20/2019

After the flow begins to fall off, and you backwash the filter, do you have to manual prime the pump or can it prime itself? Also when priming, do you have to release air out of the DE filter?
Reply

Rumit Posted: 5/20/2019

Sometimes it can prime itself, other times it can’t. It doesn’t consistently do one or the other. After a little while, it consistently stops having that good flow where debris is seamlessly drifting into the skimmer. I release the air after backwashing but that doesn’t seem to make a difference.
Reply

InyoPools Product Specialist Matt S. Posted: 5/21/2019

Give this guide a read; it may help you find the problem: How to Identify and Correct Air Leaks
Reply

RTY Posted: 5/16/2019

I have a Hayward DE 60 sq ft filter. I just backflushed it for the first time yesterday. After backflushing the pump water flow rate is much lower for some reason. Any ideas?
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InyoPools Product Specialist Robert M. Posted: 5/16/2019

Did you bleed the air out of the system using the air relief valve on the filter? That filter only requires 7.5 pounds of DE. Too much DE could cause a decrease in flow. Also, look for any air leaks on the suction side of the system.
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Shannon Posted: 5/16/2019

What would cause water pressure to come from my Polaris hook up when the booster pump is off but the pool filter is running. Is my dverter valve bad?
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InyoPools Product Specialist Robert M. Posted: 5/16/2019

Hello Shannon - It is normal for a small amount of water to push through the Polaris even though the booster pump is not running. The line to the Polaris doesn't automatically close when the booster pump is off.
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