How To Determine Why a Pool Pump Won't Prime

WRITTEN BY:  Inyo Pools

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This guide discusses the common problems involved with a motor that won't prime. Most priming problems involve leaks in the suction side of the pump (between the pump and the pool) or clogged baskets. If you have a leak on the pressurer side (after the pump), it does not affect prime. You just lose water.


Step by Step


Step 1

Pool level too low - If the pool water level is below the mid-level of the skimmer opening, there is a chance of sucking air into the circulation system through the skimmer. Enough air is the system will cause your pool pump to loose prime.

Step 2

No water in Strainer basket - Open the strainer cover and fill the strainer basket and supply lines with water for 2-3 minutes. Reseal the strainer cover.

Step 3

Skimmer basket clogged - Remove the skimmer basket and clean debris out with a hose.

Step 4

Strainer basket clogged - Remove the strainer basket and clean debris out with a hose.

Step 5

Strainer basket cover leaking - Remove the cover on your strainer basket cover. Then remove the gasket generally in a groove around the top of the strainer basket. Check that it is not cracked or has worn spots. This gasket is a common problem and should be replaced periodically. Replace the gasket in its groove and lubricate it lightly with a silicon based lubricant. Do not use Vaseline. Close the cover and hand tighten. Do not over-tighten with a tool.

Step 6

Suction or discharge valves closed - Make sure that at least one suction and one discharge valve is open so that you have a path open for the water to flow. See our guide on "How To Install a Diverter Valve on the Suction Side of a Pool" for further information.

Step 7

Leaks in glued fittings - Check for leaks in the glued fittings on the suction side of the pump. Sometimes the glue is not spread all around the pipe and you will get small air channels in the glue. Occassionally when you turn off the pump the backpressure will squirt water out this hole. In normal operation, air is being sucked into this hole. If you don't see water squirting out, turn the pump back on and drip some water around the pipe fitting joint. If you see the water getting sucked in, you have a hole. Redo the connection. See our guide on "How To Glue Pool Fixtures Together" for more instructions.

Step 8

Leaks in threaded fittings - If you have threaded fitting on the suction side of the pump, you may have a suction leak there. Try the water drip test above. If you find a leak, take the fitting apart and wrap the threaded fitting with 4-5 layers of plumbing tape. You may have to cut the other end of the pipe and re-glue it to get the threaded pipe out. See our guide on "How To Glue Pool Fixtures Together" for more instructions.

Step 9

Leaks at unions on suction side - Check for leaks around the glued connection of the unions as above. Then take the union apart and check that the O-ring is good and is seated correctly. Lubricate the O-ring with a silicon based lubricant. Rewrap the threaded side of the union with 4-5 layers of plumber's trape and hand tighten the union back together.

Step 10

Impeller is clogged - If the pump's impeller is clogged with debris, water will not be able to flow out the side slots and generate a vacuum. Without a vacuum, the pump will not be able to suck water into the pump and it will not prime. Remove the impeller and clean out the debris. See our guides on "How To Clean Out a Pool Pump Impeller" and "How To Replace A Pool Pump Impeller" for more information.

Step 11

2-Speed pump starting at low speed - When you start a 2-speed motor, it generally has to be started at high speed to created enough suction to prime the motor. After it is primed, the motor can be shifted down to low speed.


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Inyopools  Posted: 7/13/2018 

Hello Beverly - Check out our article titled "Why Are My Pool Jets Not Working?". It covers several reasons why the system wouldn't be operating correctly.

Beverly  Posted: 6/17/2018 

my pool filter system kept losing suction and the out put would virtually stop. so before i read your posts and such i checked the sand (not too dirty) checked the valve (a little stiff but workable) the pressure guage is off the grid . so i bought a new pump and i get the same result. the pump wont keep running so i'm backwashing every hour and a half or so to keep it moving, but it does not continue to circulate. HELP

Inyopools  Posted: 5/8/2018 

Hello Cory - Since every pool is different, diagnosing valve settings is tricky. You have to test the settings manually and see what works. I'm wondering if something is mislabeled because everything works when the skimmer is "closed". Is water pulling from the skimmer when the valve says it's closed?

Cory  Posted: 5/5/2018 

Just bought our home. Never had a pool, so had a service come out to do an initial evaluation and clean/chemistry check. They determined that the chlorine levels were ridiculously high and recommended draining pool about 2 feet and then refilling with fresh water. He turned off the skimmer, pump stayed on. Pump is on a timer. So, after draining, we began filling back up. This morning pool is back to normal level, we turned on the skimmer and then the pump. Pump wouldn't prime. We turned off the skimmer, pump primed and water feature and jets all operational. We then tried turning the skimmer back on and pump lost prime. Right now we are running just the pump with the skimmer turned off. Is there something we should know about this, is this normal? We are assuming this is not normal. Thank you for any help/advice!!!

Inyopools  Posted: 5/4/2018 

Hello Jeff - Have you tried opening up both the skimmer lines and drain at the same time? This will ensure that the pump is getting enough water. If it's still not priming, you may have a suction side air leak or a clog in one of the suction lines. Check out Part 1 of our article titled "Why are my pool Jets Not Working?". It has a lot of good info about correcting possible problems.

Jeff Votteler  Posted: 5/4/2018 

Just recently had a new liner replacement, which means all water was removed from system. Once the liner was replaced, and pool filled to middle of skimmer I went to go start it up. I cannot get the pump primed. When set to skimmers only seems like just a little water comes out the pipes, when set to main drain it seems I can keep filling and filling the pipes. First year this has happened. Thanks in advance.

Inyopools  Posted: 3/21/2018 

Hello Sarah - What is the pressure reading on the filter gauge when the valve is in the filter position?

Inyopools  Posted: 3/21/2018 

Hello Beldor - Hopefully, the impeller and diffuser weren't altered in any way. That is a common issue when the pumps run dry and then won't prime. How does the pump lid o-ring look? If it is cracked or leaves black marks on your hand, I would replace it.

Inyopools  Posted: 3/21/2018 

Hello RG - Check the cleaner hoses for holes. Holes in the hoses are a very common cause of air bubbles. Are you seeing air bubbles in the returns? If so, you have a suction side air leak. Besides the hoses, it could be from your pump lid o-ring, pump drain plugs, intake fitting, or your diverter valves. If there are no bubbles in the returns, the pump is cavitating and causing vapor bubbles. If this is the case, you'd have to feed the pump more water by opening up the skimmer or main drain.

Rg  Posted: 3/21/2018 

There are a lot of bubbles in pump basket when pool cleaner is on. We were told that is normal cause the Hayward Tri star pump is designed to draft when pool cleaner is on. Is that right

sarah  Posted: 3/19/2018 

When I put the filter in circulate position the pump works and is pulling water but when I put into filter position I lose pressure and the pump won't pull water. I took filter apart and nothing is cracked and my filter is clean no broken grids and I put new DE. I don't know what could be the problem.

Beldar  Posted: 3/10/2018 

I have a pump that now won't prime. Sometime over the winter (the pool pump runs for 6 hours a day every other day) evidently it lost water flow and the plastic strainer basket on the pump housing melted and got sucked into the impeller. I took the pump apart and everything looks fine, put it back together and still won't prime. Any ideas?

Cindy  Posted: 2/17/2018 

Thank you so much for posting the DIY videos. I now know what an impeller is, how to clean it and how to prime the pump. All working again, thanks to you!

Inyopools  Posted: 1/9/2018 

Mike P - It sounds like you may have reduced flow in one of your Spa lines caused by a partial blockage. Try snaking a line down each of the spa lines to loosen it up or try blowing it out with a King Drain hose adapter. I tried to think of what else could have happened when your pump failed that could have contributed to your problem but could not think of anything.

Mike P.  Posted: 1/5/2018 

Stumped!!! 30,000 gallon pool with in ground spa, spa water level is 3 feet higher than pool water level (raised spa). Hayward super pump 1.5 hp. 2 1/2" pvc all around. Has worked fine for 12 years. One day, heard pump turn on and it was whining. I go check it and pump basket is not primed. Basket is warped from heat, etc. I figure, well, the pump just gave up the ghost, lost its prime after 12 years and failed. So, buy new hayward super pump. install myself. no problems. However, I went to use spa and in spa mode (pump drawing from spa and returning to spa), the pump basket would only be 1/2 filled. As soon as I switch to pool mode (pump drawing from pool and returning to pool), the pump basket would fill. PSI readings during pool mode 20psi, spa mode 33psi (small spa) PSI's unchanged from new. I've soaked and cleaned filters. I've even ran the cartridge housing without the filter cartridges and PSI is still 20/33 pool/spa mode AND pool mode works fine, spa mode still has pump basket with half water. The biggest problem is the heater for the spa will pop and act like its boiling the water off during spa mode. Pool mode it runs fine. At one point during my struggle, I put the pump in spa "empty" mode and it failed to empty the spa all the way. It drew the level down to about a foot of water and stopped. There is only one 3-way Jandy valve between the spa/pool and pump. It selects where the water draws from. My first suspicion was a leak at this valve. I have replaced the o-rings in this valve and the valve appears to not be leaking. I do have small leaks on the pressure side of things. One at the pump outlet (I didn't use enough teflon) and one at the other Jandy valve, which i just need to replace o-rings. but until i find this culprit and rule out replacing the whole works, I'm gonna wait on those. Help me not call a "professional" to come charge me $1,000 to diagnose this.

Inyopools  Posted: 12/27/2017 

Zachary - If your pump was running dry, there is a good chance, as you indicate, that your shaft seal was damaged and would need to be replaced. And as long as you are replacing the shaft seal, I would buy a GOKIT and replace all the pump seals. Also, while you have the pump apart, you can check for a plugged impeller. It's a common problem.

Zachary  Posted: 12/19/2017 

This afternoon I found the water was not going into the skimmer. It turns out, the pump was not priming for who knows how many days. The motor sounded normal. When the motor was on it would suck all the water out of the basket area while very a slow stream of water came from the pool. Is the shaft seal the only possible culprit? Or could the impeller be clogged? Thanks for the help.

Missy  Posted: 10/26/2017 

The bearings in our motor went out so we had to replace the motor. The pool was turned off for 9 days while we dealt with this. We replaced the motor today and turned it on. The motor is running but it doesn't sound like it's even trying to prime. There is no movement of water in the strainer basket. I checked all the valves and everything is open (I had it closed for the 9 days.) I tried filling the strainer basket - no change. I put the garden hose in the skimmer suction hole - no change, but now the pool is very full. Any suggestions?

InyoPools Product Specialist Dennis R.  Posted: 9/13/2017 

Akiko - When your pump runs dry for a period of time, it generates a lot of heat that can damage your shaft seal and pump gaskets. I would recommend buying the GOKIT for your pump and replacing all the gaskets/seals. See our guides on "How To Replace a Pool Motor Shaft Seal" and "How To Replace Pool Pump Gaskets" for more information.

Akiko  Posted: 9/5/2017 

This morning I found the water was not flowing into the skimmer. It turns out, the pump was not priming for who knows how many days. The motor sounded normal. I tried Step 2, and saw a leak under the motor. When the motor was on, the leak stopped, but sucked all the water out of the basket area while no water came from the pool. Is the shaft seal the only possible culprit? Thank you for your help.

InyoPools Product Specialist Dennis R.  Posted: 9/4/2017 

Sheree - It sounds like you may have a large suction leak on the suction side of your pump. As your pump builds up pressure, it could be sucking in enough air through this leak to lose prime. Check for leaks at the base of your skimmer, any of your suction side diverter valves, any suction side unions, the O-ring under your pump cover and the suction side drain plug at the base of your pump.

Sheree  Posted: 9/3/2017 

I have been having such a problem with my pool! It's green more than it has been blue! It will prime, but it will not keep its prime. Within 3 minutes (or less) it stops. We had someone come out and "fix" it.....$650 later and it is still doing the exact same thing. We replaced the suction line that leads into the basket, the propeller is clear and I am at a loss! Please help!!

InyoPools Product Specialist Dennis R.  Posted: 8/22/2017 

ceci - Check the O-rings of the old pump against the O-rings of the new pump to make sure the new pump has them all. Priming issues are in the front end of the pump, so check the strainer cover O-ring and the diffuser gasket first.

ceci  Posted: 8/21/2017 

I replaced my pool pump because it makes noises with a CENTAURUS Swimming Pool Pump 2.7HP 2000W Electric Self Priming Spa Water Filter, both exactly the same brand and model, but the old one stills work and the new one doesn't suck water

Waterfall problem  Posted: 7/23/2017 

I have a waterfall/pond which I'm having problems with. During the day it appears to run fine. I usually run it from 4pm to 10:30. In the morning the basket loses water and doesn't have enough to prime. I've replaced the pump and sealed the lid. Any suggestions or ideas what I could do to determine the problem.

InyoPools Product Specialist Dennis R.  Posted: 7/10/2017 

Anonymous (priming) - When you turn your pump off, does water surge backwards from the pump to the skimmer? If so, you may have a suction air leak before the pump that allows air to build up in the top of the tank. This cause backpressure which pushes the water out of the pump and front pipes when the pump is turned off. See our guide on "How to Identify and Correct Air Leaks".

Anonymous  Posted: 7/8/2017 

My pump won't prime on startup so I fill the strainer basket and all works fine. Pool is full, no loss of water level, impeller is clear and seal on basket fine. What's causing the lose of the prime?


InyoPools Product Specialist Dennis R.  Posted: 7/3/2017 

Anonymous (priming pump) - When you try to fill the strainer basket, all you are trying to do is yet some water into the pipes before the pump. Some baskets, depending on their relative height to the pool, will not fill or will not retain the water. Fill the pipes and close the cover quickly, then turn the pump on. There should be enough water in the pipes to prime the pump.

Anonymous  Posted: 7/1/2017 

I have tried to fill up the pump basket as suggested in step 2, but the basket will not fill up. Even with me leaving the water hose running for awhile. Which means in order for me to turn the pump back on, there will be no water in the basket. What could be the causing the pump basket not to fill up?

Thank you,
Desperate Texan

InyoPools Product Specialist Dennis R.  Posted: 7/1/2017 

Diane - Hopefully your problems are not underground. I would first check the gaskets and connections at the pump and between the pump and the skimmer. Check the O-ring on the pump's strainer cover first. See our guide on "How to Identify and Correct Air Leaks" for more information.

InyoPools Product Specialist Dennis R.  Posted: 6/30/2017 

Maggie - It sounds like you have a suction leak that is causing backpressure in the top of the tank. I would still look at replacing the pump basket gasket. When you are in recirculate mode, the filter is bypassed. Any air coming into the system is routed right back to the pool so that air cannot build up in the filter.

Diane  Posted: 6/30/2017 

Awe have tried to prime basket with Jose water however water still not coming thru could leak be in line that runs from skimmer box to pump which is under ground thank uou

Maggie  Posted: 6/28/2017 

I have a 30,000 gallon pool with a super Hayward pump. The pump seems to pull vacuum fine in the recirculate mode but once you move the indicator filter it seems to loose water in the filter basket after an hour or so. Changed O rings on the filter, have suction in the pool both summers and main, and have tightened all union connections. Any suggestions on what could be causing this. I thought pump basket gasket but it doesn't loose anything in the recirculate mode as stated.

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

Michele - No, a cut gasket would leak and when they are stretch like that, they tend to overlap on themselves and also leak. Your stretched gasket should be replaced with a new one.

michele  Posted: 6/17/2017 

I took the seal off our skimmer on the pump and brought it to pool supply. They looked at it and said it was fine. When I put it back 2gthr the square ring was stretched out. Can I cut it to make it fit?

InyoPools Product Specialist Dennis R.  Posted: 5/30/2017 

crazy4brady - I would have recommended a 1 1/2 HP single speed or varialbe speed pump for your size pool. If you can afford the initial purchase, a VS pump can save you up to 80% of your operational costs. A couple other things to check. Make sure the pump's impeller is not clogged. See our guide on "How To Clean Out a Pool Pump Impellers ". And when you purchased this pump, did you buy the right one. If you have an in-ground pool, you need an in-ground pump. Above ground pool uses an above ground pump. An AG pump is installed at the base of the AG pool because it need gravity to prime the pump.

crazy4brady  Posted: 5/28/2017 

We purchased a Doheny pool pump 1hp for our 20x40 pool. We have always used 1 1/2 hp in the past but were told 1hp would be enough for our pool size. We have trouble keeping this pump primed. We replaced the skimmer and skimmer line last spring, so we know that it's not that. What could be causing the problem?

InyoPools Product Specialist Dennis R.  Posted: 5/14/2017 

Anthony - If your housing gasket has a leak, you would see water squirting out at the break when the pump is operating. Did you replace the other motor pump gaskets when you replaced the motor? As a minimum, you should have replaced the shaft seal. All the pump gaskets are sold in a package called a GoKit. The GoKit for your Sta-Rite Max-E-Pro pump is GOKIT79.

Anthony  Posted: 5/11/2017 

I purchased a pump motor to replace a worn one from Inyopools, replaced the gasket on the pump housing (Sta-Rite Max-e-Pro) and it works fine until the pump is shut off. Then all the water drains out of the basket and it loses prime.

It seems like the new gasket is the problem, how can this be?

InyoPools Product Specialist Dennis R.  Posted: 4/26/2017 

Pmw - I'm not sure what you are referring to as "the little bottle on the pump". If you are referring to the little (1 1/2") bottle on the side of your filter's multiport valve, you don't have a problem. This bottle only fills up when you are backwashing the filter. It tells you when the waste water changes from dirty water to clear.