How To Determine Why a Pool Pump Won't Prime

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This guide will explain how to troubleshoot a pool pump that is not priming. The most common causes of pool pump priming issues are sucking air leaks in your pump housing or plumbing, and debris clogs. We’ll be focusing mainly on the suction-side of your pool equipment for this guide. The suction-side s all equipment and plumbing from your skimmers and main drains to your pool pump’s impeller.

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Video

Step by Step

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Step 1

Low Water Level - The pool water level should be kept at about halfway up the skimmer weir door; maintaining this water level allows enough water through during ebbs and flows to prevent the skimmer from gulping air. 

How to Identify and Correct Air Leaks

Step 2

Missing Skimmer Basket - A missing skimmer basket will introduce any debris captured by the skimmer into your pool’s plumbing line. The debris can build up to become a clog.

Related Article - How to Unclog a Pool Skimmer

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Step 3

Clogged Pump and/or Skimmer Baskets - An overfilled strainer basket restricts water flow, which makes priming more difficult. Cleaning your strainer baskets regularly, or at least make a habit of inspecting them weekly.

Related Articles - How To Clean Out the Pool Pump Strainer

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Step 4

Air Leak - Pump Lid and Pump Lid Gasket - Remove the pump lid from the strainer housing to check for warping, cracks, or issues with its thread (for screw-on lids only.)

Remove the lid gasket from its groove checks for signs of aging (cracking rubber) or pinches. An easy way to determine if your gasket is past its usefulness, rub your fingers along the gasket; if a black rubber streak rubs off on your hand, it’s time to replace the gasket.

Quick Tip: Check for gasket deterioration by running your fingers along its length. If your gasket’s rubber has started to degrade, you’ll see heavy black smudges on your hand.

Related Articles - How to Identify and Correct Air Leaks

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Step 5

Adjust Diverter Valve Settings - Make sure that at least one suction and one pressure (return) line are open to allow water to freely pass through your system. 

Quick Tip: if not already, take this time to label your diverter valve ports; labeling will help prevent diverter issues in the future. Calves can be marked using homemade laminated labels.

Related Articles - How To Install a Diverter Valve on the Suction Side of a Pool


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Step 6

Air Leaks - Glued Joints - Small air channels can form in glued plumbing joints; these cracks can form due to age, or soon after initial installation if glue was not thoroughly applied.

To identify problem joints, look for water spouts that pop up when the pump is turned off. When the pump is turned off, backpressure will force the water to backwash to the pool. The backflushing water will force its way through the cracked glue, providing ng a marker for where to inspect next.

Related Articles - How to Test for Suction Side Air Leaks

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Step 7

Threaded Fittings - Use any of the techniques mentioned in the “How to Test for Suction Side Air leaks guides to find the leak. Once found, disassemble the joint union or adapter then apply 2 to 3 turns of Teflon tape to the threads. Before applying new tape, remove any bits of old tape or dirt from the threads.

Related Articles - How to Test for Suction Side Air Leaks

Step 8

Clogged Impeller - Impeller vanes can become clogged with mud, pine needles, or any type of bulky debris. As the impeller gets more congested, the lower the pump’s flow rate will drop. A precursor to priming issues is a drop in return jet flow rate.

Related Articles - How To Clean Out a Pool Pump Impeller

Step 9

Pump Speed Set Too Low - If you're priming issue started after installing a dual-speed or variable speed pump, the priming speed may be set too low for your system. Reference your pump’s owner manual for instructions on how to reset the initial priming speed.

Related Articles - Best Setup For Variable Speed Pool Pumps 

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Comments

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(1 to 40 of 181)

 Posted: 5/27/2022 

We just opened our pool and left the pump running overnight not paying attention. We were cleaning the baskets as they were clogging from algae. After leaving it on all night we woke up and found the basket full, pump not pumping water and very hot. We shut everything down and cleaned everything. After pump cooled off we started it again. Now it will only keep prime for a few minutes for it looses it. Could we have damaged the impeller or diffuser? Or maybe we burned up the seal and it's stucking in air now? If I put the filter in bypass pump will prime but not if I leave it in filter mode.
 Reply

InyoPools Product Specialist  Posted: 5/27/2022 

It could be any one of those causes; the best way to find it is to check for damage by opening and inspecting the pump. The fact that it won't prime when the filter is set for regular operation could signify you need to do a thorough backwash and rinsing.
 Reply

 Posted: 10/14/2021 

Pump won’t prime. I have poured water into the strainer box for about half an hour straight and still no raise in the water level. It will raise up over the strainer box occasionally, but when I pull the hose out the water level drops just above the top of the inlet valve. Hit the pump and the water gets sucked through the pump but no flow is created.
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InyoPools Product Specialist  Posted: 10/14/2021 

Ok, you've done one thing from the guide. I suggest doing the rest of the steps we walk you through to find the issue. Everything I'd suggest is already written in the guide. If you do all that and then still can't find it, then I'd come back with a follow-up.From that basic description in the question, you may have a water (or air) leak or the water level in the pool is low. But you won't know until you do the other troubleshooting. How to Identify and Correct Air Leaks
 Reply

Anonymous  Posted: 10/2/2021 

All of a sudden my pool is not priming when starting. if i open relief valve, within a minute pump starts to prime and than continues to run fine until next start and have to do all over
 Reply

InyoPools Product Specialist  Posted: 10/4/2021 

If the only way to get your pump to prime is to release a large amount of trapped air in the system, then I suspect you have an air leak. I begin troubleshooting by looking for the air leak on the suction side of your system. Follow the steps in this guide to find the leak - How to Identify and Correct Air Leaks
 Reply

 Posted: 5/22/2021 

Just bought a new pump as old one fried. Repeated ALL steps with no luck as pump will not prime. No air leaks, no water leaks, all joints and unions properly taped and/or glued. Lines full and not leaking, pump basket clean and full, skimmer clear, etc ,etc. Any ideas?
 Reply

InyoPools Product Specialist  Posted: 6/4/2021 

Have you tried priming the pump yourself using a hose? How To Prime a Pool Pump
 Reply

 Posted: 5/17/2021 

Opened pool for the third season. Started off with just the drains open on the suction side until the water level was back up. All was great. Opened our two skimmers today and the pump lost prime. Added a little more water. Now the pump is fine with the drains and one skimmer at a time open. As soon as we open two skimmers and the drain together it loses prime. Doesn’t matter which skimmer. Both are good in their own. Any time all three valves are open we pose prime. I backwashed and rinsed the filter and still have the same problem. Cleaned the skimmer basked and the basked at the pump. No luck. Any suggestions?
 Reply

InyoPools Product Specialist  Posted: 6/4/2021 

You may have an air leak, which you should try to find using the How to Identify and Correct Air Leaks guide.
 Reply

 Posted: 5/1/2021 

Just opened my pool, new pump installed last season, new filter cartridges and manifold this season. Pump won't prime. I've put a hose into the pump 2-3 minutes, I can even see the water flowing backwards through the skimmers. When I turn the pump on, it sucks with authority, but the water doesn't continue to flow and it doesn't prime. I've tried to open / close the suction valves, nothing seems to be changing. I don't see any swirl at the skimmer. If I open the pump lid, the basket area fills with water, then if I close and start the pump again - it will suck with authority until the water flow stops. Only thing that has changed are the filter cartridges...but I don't think the problem is after the pump. It almost seems like all the valves are closed, but then it wouldn't suck. I can also see water flow on the return side, so I'm stumped...everything appears to be "ok" (weir doors open, water level is high, etc). Any ideas?
 Reply

InyoPools Product Specialist  Posted: 5/14/2021 

Are you sure you aren't confusing an absence of air bubbles in the pump strainer for it not priming? I presume no bypass circumvents your pump and filter, so water has to be pulled in by the pump and pushed out of the return.Also, are you sure you installed the correct cartridges? Some filter models have cartridges that are similarly sized, but the amount of pleats (and fabric used) is drastically different, affecting flowrate capacities. If a smaller cartridge was used it could explain the sudden dropoff in flow after a few minutes.
 Reply

 Posted: 1/27/2021 

My pool has been decommissioned for about 12 months, have tried to prime by filling pump and by compression from inside the basket. No blockages it sucks initally for a couple of seconds then stops. Any advice thanks in advance.
 Reply

InyoPools Product Specialist  Posted: 1/28/2021 

The guide mentions quite a few things to check. If your pool was out of service for awhile you should do those basic things before a more technical troubleshoot is attempted. If you have done more than try to prime the pool, then please provide more info.
 Reply

 Posted: 10/4/2020 

is is possible to have something stuck in the line under the concrete?
 Reply

InyoPools Product Specialist  Posted: 10/5/2020 

Yes, you can get a blockage there as well. Wherever there is liquid going through a pipe, there is a chance of a blockage. A plumbing snake or plumbing bladder would be a good option for clearing a blockage.
 Reply

 Posted: 8/16/2020 

Just installed new motor. Matched exact one that burnt out. Pump will not self prime. Nothing else changed. Is there a switch on the motor?
 Reply

 Posted: 9/20/2020 

Hi Mike did you get it sorted? We are having a similar issue
 Reply

InyoPools Product Specialist  Posted: 8/21/2020 

Have you tried any methods to help the pump prime itself, like filling the strainer with water? Does your filter have an air relief; and if so, is it open? I would also check any plumbing valves to make sure they are set to pull water from the main drain.
 Reply

 Posted: 8/11/2020 

We have just replaced our Pentair Superflo VS pump. It has been installed and seems to work just fine, except that our skimmer baskets are not pulling water. We have cleaned the impeller, the cartridge filters and bleed the air, and cleaned the salt cell. Any ideas for more troubleshooting?
 Reply

InyoPools Product Specialist  Posted: 9/3/2020 

Have you made sure your diverter valves are open on the skimmer line?  To help pumps prime, an installer will set it so only the main drain is drawing water. If they forgot to put it back to open, it could explain your flow problems.
 Reply

 Posted: 7/7/2020 

I have a problem.I have a cartridge filter,when I install the filter the pump is sucking water for 3/4 of the capacity.The kreepy is hardly moving. When I remove the cartridge filter and let the pump running it is sucking water for 100%. I checked everything but can not find the problem. Do you have a solution for this problem ?
 Reply

InyoPools Product Specialist  Posted: 10/6/2020 

It definitely sounds like the cartridge is restricting flow. Is this a new cartridge or an old? If it is old, you probably need to give it a chemical soak to clear out debris. How To Chemically Clean a Pool Cartridge Filter
 Reply

 Posted: 2/15/2020 

80’s gunite pool, new house for us. Mechanical equipment about 10 years old. Variable speed pump, cartridge filter, heater, pool and spa. At some point someone repiped things, my main drain has no suction. There are two pipes coming up out of the ground near the pump. One is 1 1/2 inch, the other is 2 inch. These are capped off but have notches cut into them below the cap. Someone explained this is how the spa aerates. I determined that the 2 inch pipe actually aerates the spa jets. The other apparently does nothing. I recently pressure washed my four filter cartridges. They had probably not been cleaned in at least five years, maybe ever. My Hayward variable speed became a monster at 3300 rpm and the 1 1/2 inch capped but notched pipe started spraying water out at anything over about 2000 rpm. I think the actual efficiency of the pump was at least half before I cleaned the cartridges. I cut this pipe and capped it permanently as I could not determine its use. This did not seem to have any detrimental effect on anything. However, my pump has problems priming, as if it’s trying to push a head of air, and often will blow water backward through the suction lines when the pump is shut off. When it primes, it runs like a bandit, but it seems to be compressing air in my filter housing. I can bleed air from the filter until I get to water, but this seems not to be a common thing to have to do. Basically, it seems like my pool ran better with clogged filters, as not I seem to have nothing but problems with back pressure and priming, whereas before cleaning, I never had issues at all other than looking at a pressure indicator deep in the red on the filter. What might I have done wrong, and what the hell do you think that 1 1/2 inch pvc blowing water might have been.
 Reply

InyoPools Product Specialist  Posted: 2/17/2020 

First, what troubleshooting have you done from the guide? As you say, there is air in the system; most of the guide discusses how to prevent air from getting in your pipes. What steps have you taken to detect or correct air leaks? You can also try this more in-depth guide on finding and correcting air leaks: How to Identify and Correct Air LeaksThe act of cleaning the filters should not cause pump priming issues. If the filter or pump were reassembled incorrectly (lid or clamp is not tight enough, the gasket is pinched) that is most likely the issue.Also, did this priming issue only start after you cut the strange with no function?
 Reply

 Posted: 10/20/2019 

New pool.owners here Every time we clean the filters we have an issue w priming from full pool suction. If I adjust to partial spa suction it gets it moving but from full pool it causes dry prime alarm to sound. Any suggestions?
 Reply

InyoPools Product Specialist  Posted: 10/21/2019 

Your water level may be too low, which allows the pump to gulp air. You can also still check the plumbing elements we mention in the guide to determine if they may be causing the air in the system, i.e., valves, unions, joint adapters.
 Reply

 Posted: 10/15/2019 

just changed my old 1 speed to a variable speed ECM27SQU. After 1 full day of operation, here are my results : 2h at 3450 pump is primed at 98% (small size air bubble); 2h at 2600 pump does not quite prime (air bubbles in most of the lid); 8h at 1725 and there is little/no priming (about 4-5" of water in the basket; almost no pressure at the filter meter reading, but water circulates). Also at 3450, my inline cleaner was working, but once it dropped to 2600 (and of course to 1725) the cleaner stopped working; i then closed the cleaner valve hoping to suck more water out of skimmer and main, but that did not change much; pump was still not priming anymore. I then did the soap water test and could not find a leak around any fitting or valve or lid. Water is about 1/2 way to the skimmer. What should i do or look for next ?
 Reply

InyoPools Product Specialist  Posted: 11/4/2019 

So with a variable speed motor you may not see a pump with a full prime as the suction has decreased. When the RPM's are lower and the suction is lower, your cleaner potentially not having enough suction is normal. Not all pool systems will generate enough suction and water pressure in the lower RPM's. Each swimming pool is different however after testing the settings, not having any air suction leaks and seeing water flow back to the swimming pool in at least some of the lower RPM's you do not have to be concerned. 
 Reply

 Posted: 9/4/2019 

My pump looses suction within a minute whenever I connect the hose to vacuum the pool. The pump runs 6 hrs every night with no problems. As soon as the hose goes on the skimmer box cover , the pump noise changes as if cavitating . I bought a brand new hose and still the same. Tried a new vacuum head also , as old one warping . I replaced the 8 yr old pump with the same ( Davey Silensor ) because it had a broken impeller when I opened it up to investigate. I am baffled as there is no obstruction. Has anyone got any idea ?
 Reply

InyoPools Product Specialist  Posted: 9/4/2019 

Hello David - Do you have an above ground or inground pool?
 Reply

 Posted: 9/4/2019 

I have a 55,000 litre concrete in ground pool that is 25 yrs old.
 Reply

InyoPools Product Specialist  Posted: 9/5/2019 

The pump is not receiving enough water when the hose is plugged into the skimmer. Try opening up the main drain more so that it can pull additional water.
 Reply

 Posted: 8/7/2019 

I think he went through everything and i had 3 things that he mentioned was the problem
 Reply

 Posted: 8/2/2019 

This guide is awesome. Thank you for making it.
 Reply

Anonymous  Posted: 7/7/2019 

I cant get my filter to prime. I sit there and fill the water for 5 minutes or more and it never fills all the way up. After I turn it on it immediately drains from the filter and starts sucking air. I tried all methods above. Please help.
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InyoPools Product Specialist  Posted: 7/8/2019 

This is a more thorough guide on How to Identify and Correct Air Leaks. If you still can't find the issue after following the guide then you may want to try calling a professional to take a look. 
 Reply

 Posted: 6/19/2019 

I have a pump that will prime but loses it when the filter basket is almost full. At that point the water in the basket area drains away and I can see the water coming from the pool to start filling for prime. It just repeats that cycle and never runs in normal filter mode (or backwash for that matter). Any thoughts? Thx in advance Scott
 Reply

InyoPools Product Specialist  Posted: 6/20/2019 

It sounds like you have a sucking air leak. Have you checked any of the things mentioned in the guide? How to Identify and Correct Air Leaks
 Reply

 Posted: 6/2/2019 

Pump not getting enough water to return
 Reply