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: 06/19/2017 14:25 PM  Inyo Product Specialist

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: 06/17/2017 19:14 PM 

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  Posted: 05/30/2017 10:36 AM  Inyo Product Specialist

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: 05/28/2017 15:08 PM 

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  Posted: 05/14/2017 16:38 PM  Inyo Product Specialist

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: 05/11/2017 9:38 AM 

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  Posted: 04/26/2017 10:22 AM  Inyo Product Specialist

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.

Pmw  Posted: 04/25/2017 18:26 PM 

I finally got my pump primed. Still unsure of what the problem was as never occurred before. Now the little bottle of water on the pump won't fill up with water. What can I do and should I not run pump until it is full?

Inyopools  Posted: 04/17/2017 12:22 PM  Inyo Product Specialist

Tomasz - I'm not sure I understand your question. Is the switch at the "T" a diverter valve that allows you to shut off the main drain but you have no way of inserting a hose at or around the pump going to that "T"? If so, you might consider putting unions on the input and output ports of your pump that would allow you to remove the pump and give you access for the hose.

Tomasz  Posted: 04/16/2017 18:26 PM 

You said: "Try blowing the clog out with a drain cleaner bladder. It’s most effective if you insert it at the pump going back to the pool." How do I do that? The pipe from the pump has a tee with the switch between the skimmer and main drain. I have no access to the pipe after that ...

Inyopools  Posted: 03/31/2017 12:57 PM  Inyo Product Specialist

anonymous (cover O-ring) - No, I would not glue the strainer cover O-ring down. I would suggest lubricating the top of the O-ring when each time you replace the cover.

Anonymous  Posted: 03/30/2017 6:11 AM 

I replaced the strainer basket o-ring because I was having issues with air getting in. There was a residue left underneath; it looked like the previous o-ring had been glued down but the o-ring came up easily and all intact?. I had to scrape out the residue with a screwdriver, which was not easy to remove but you could tell it was somewhat flexible. When I lift the lid now the o-ring comes out every time, but it did not use to, which is frustrating. Should I "glue" my o-ring down? If so, what do you use? Thank you!

Inyopools  Posted: 03/28/2017 12:58 PM  Inyo Product Specialist

Este - Generally, when you add water to the basket, some of it does flow back into the pool. You are just trying to get some water into the system to partially fill the input pipes. If your system won't prime with partially filled pipes, you might replace the strainer basket O-ring. It may not be sealing properly.

Este  Posted: 03/27/2017 9:35 AM 

When ever my pump needed priming, I used to add water to the pump basket for about 3 mins then water will fill the pipe going to the pool and fill the basket. I will close lid and start the filter and everything would be fine. The issue now is I cant fill the basket any more. Water just flows into pool and doesn't fill the pipe and basket. Any ideas? Thank you.

Inyopools  Posted: 03/23/2017 16:29 PM  Inyo Product Specialist

Tony - If you shut the pump off right away, you should be ok. Try running water into the pump's strainer basket to fill up some of the lines before you turn the pump on. Before you reattach the cleaner, hold its hose under water to eliminate the air in the hose.

Tony  Posted: 03/21/2017 23:06 PM 

I connected a manual cleaner while the pump was working, it immediately lower the pressure due to the air in the hose. After that the pump hasn't been able to prime. Did I mess up the pump?

Inyopools  Posted: 03/20/2017 11:54 AM  Inyo Product Specialist

Paul – You should see a part number on the underside of the cover. Put that into our customer page and it will point you to a parts list for this pump.

Inyopools  Posted: 03/20/2017 10:13 AM  Inyo Product Specialist

FlaPool - Sounds like you may have a clog in your skimmer/vacuum line. Try blowing the clog out with a drain cleaner bladder. It's simple, cheap and most people have had good success with them. It’s most effective if you insert it at the pump going back to the pool. Shut off the main drain before attempting to blow the skimmer/vacuum line out. Any hardware store sells these bladders.

paul  Posted: 03/19/2017 13:58 PM 

My pump basket lid has a flattened O-ring so pump will not prime. Where can I get new O-ring? Inside diameter of O-ring is 5 inches; outside is 5 1/2 inches, or very closely those values.

FlaPool  Posted: 03/16/2017 18:40 PM 

Skimmer/Vacuum stopped working "all of the sudden" - will not prime. Main Drain is fine and flows extremely well. Open skimmer/vacuum line - flow stops. Close that line, flows again fine. What is going on?

Inyopools  Posted: 03/06/2017 13:09 PM  Inyo Product Specialist

tw - Try pulling the motor out of the pump to check the impeller more closely for debris. Then try filling the strainer basket with water again to fill pipes that may have completely drained. Re-check the rest of the steps in this guide. I assume you haven't had a hard freeze that may have broken something on the suction side of the pump.

tw  Posted: 03/05/2017 17:46 PM 

I have a 30,000 gallon inground pool. I replaced the pump a couple of months ago which I purchased from INYO pools. It worked like a charm. I have turned it off a couple of different times this winter for a month at a time to save on the energy bill. It reprimed each time until now and I can't get it reprime now. Nothing has seemed to changed. I have check the impeller, seals look good, all baskets clean. Just don't understand why it will not work now.

Inyopools  Posted: 02/17/2017 11:32 AM  Inyo Product Specialist

Kingy70 - You new pump may be underpowered. Did you replace the old pump with a smaller pump? Did you replace the pump with an equivalent pump? Look at the Total HP (THP) of each pump. The product of the listed HP and the Service Factor (SF) - both on the motor label - will give you the respective THP. These products must be the same to have an equivalent pump. Lastly, do you have a working check valve between the pump and the solar panels? This valve will keep the water in the solar pipes and panels from emptying when you shut the pump off causing the pump to refill the solar system on startup.

Kingy70  Posted: 02/15/2017 6:18 AM 

just changed my solar heater pump. Pump now takes forever to get enough flow through to get the water circulating. When it does there is not enough flow to ensure the system is operating at maximum. it sounds like the water is just trickling down the return pipe. How do I get the air out of the lines to ensure max flow?

Inyopools  Posted: 12/12/2016 10:37 AM  Inyo Product Specialist

Eric - Since the only change you made to your system was to add the heat pump, I would concentrate on it. Sounds like the heat pump was not installed correctly. You should not have seen the PSI increase. The heat pump should not make that much noise. And the pump should not prime slower that before you added the heat pump. I would have the heat pump installer come back and check the heat pump installation.

Eric  Posted: 12/06/2016 20:45 PM 

#1: I just had a heat pump installed on my pool. Pryor to the install my filter had a 12-16 PSI. After the install my filter is at 25-29 PSI. The spider valve is 1 1/2" enlarging to 2" about 2' away. Heat pump is about 10 from filter. Is the PSI increase normal?
#2: The water going through the heat pump is very noise (louder than the pool pump. Is this normal?
#3: One jet at the pool has constant air coming from it and the strainer basket doesn't hold a good prime (take 15 to 20 seconds to prime after being shut off). Any suggestions other than changing out the skimmer lid gasket and the gasket connecting the pump and skimmer?

Inyopools  Posted: 11/05/2016 11:43 AM  Inyo Product Specialist

Rerun - Make sure your VS pump is starting up in high speed to get the suction required to prime the pump. If that's not the issue, you might consider adding a check valve between the pump and the pool so the water doesn't flow backward into the pool when the pump is off.

Rerun  Posted: 11/05/2016 9:58 AM 

Just purchased a new Hayward MaxFlow variable speed pump. I had to re-orientate the inflow pipes to fit. Pump initiated a self prime and worked fine - pressure was strong and no apparent leaks. The next day pump turned on but there was now water inflow. I stopped the pump - pulled the skimmer basket and manually filled with water. Pump primed and works fine. However, this happened again the following day and repeated. Need help as I can't keep having to manually prime the pump each time.

Inyopools  Posted: 11/04/2016 12:41 PM  Inyo Product Specialist

Jose - One of the most common problems for low pressure is a clogged impeller. See our guide on "How To Clean Out a Pool Pump Impeller" for a simple fix. If that doesn't solve your problem, see our guide on "How To Determine the Cause of Low Water Flow".

José  Posted: 11/03/2016 2:41 AM 

I have a problem with my system. It was running smoothly until two days ago, and nothing out of the ordinary was done.The water is circulating but my cleaner is not moving due to low pressure. I have taken all the pipes out and placed my hand over the hole in the wier (where pipes connect) and very ow pressure. Water flows nearly 100% out of the jet. The baskets are all clean, the impeller seems to be clear (it moves freely when i rotate it with my hand). There is no noise coming from any of the pipes that run from the cleaner to the wier. The water level is also correct.

Inyopools  Posted: 07/30/2016 14:10 PM  Inyo Product Specialist

peter78312 - If you can run one or the other function at a lower speed, it might save you money to split them out. You may have to run the slower function longer to filter all your water.

Anonymous  Posted: 07/28/2016 2:52 AM 

Thanks for the help. I re did the piping on both sides of the filter and it fixed the prime. I think the last time i cleaned the impeller I must have jarred a connection and created some air in the line. fixed now.

One last question i have a 3 way jandy valve that comes from the filter and splits back to the pool sweep pump on one side and the other to the solar pre heat. It has a electronic valve actuator. During the day when i am both filtering the pool and running the pool sweep should i seperate out the function? meaning the first 2 hours are sweeping the pool and the 2nd 2-3 hours are pumping water thru the solar pre heat?

Thanks again for your help. It has helped immensely.

Inyopools  Posted: 07/25/2016 11:10 AM  Inyo Product Specialist

peter78312 - If your pump won't prime when the filter is in the Recirculate setting, your problem is not in your filter. Recirculate bypasses the filter - water comes in from the pump and is immediately diverted back to the pool without going through the filter. Assuming you have an in-ground pool, is your new pump an in-ground pump. An above ground pump will not be able to suck the water from the pool to the pump. Check also that your pump's impeller is not clogged with debris. As far as having too much sand in the filter, that should not affect priming, but it may affect backwashing when your system is up and running. You should have 6" to 12" of space between the sand and the top of the tank depending on the filter model.

Anonymous  Posted: 07/23/2016 15:34 PM 

Thanks for the response. So i replaced the sand, replaced the jandy valve, replaced the lateral assembly and it still wont prime in either recirculate or filter mode. I followed the instructions on the way to fill the sand filter and i have 500 lbs of sand in there give or take a few lbs maybe. Could too much sand cause the pump to not function? does it just take a while to get the laterals circulating after filling the sand?

Inyopools  Posted: 07/15/2016 9:11 AM  Inyo Product Specialist

Peter78312 - See if your pump primes in Recirculate mode. If it does, you have a filter issue. If you haven't changed the sand in 5 years or so, you might try that. Check the spider gasket in your multiport valve to make sure it is not damaged. Check that your pump powers up in high RPMs and then drop back to a lower level after it has primed.

Peter78312  Posted: 07/14/2016 22:02 PM 

I have a new intelligence variable speed pump and I can prime the pump when I am back washing the Hayward jandy sand filter but but when I switch to filter I can't get the pump to prime. I am confused as to what is happening here.


Inyopools  Posted: 07/05/2016 10:41 AM  Inyo Product Specialist

grace - It sounds like you are getting air through the skimmer when you are vacuuming. Make sure your skimmer basket has enough water in it to cover the hose connections. Also, your may have holes in your cleaner hoses or connections. Hold the cleaner hose under water while the pump is on to see if the pump primes. If it does, sequentially lift each section of the hose above the water surface to see when you lose prime.

grace  Posted: 07/01/2016 21:43 PM 

I'm trying to vacuum the pool (new at this). Vacuuming to waste with main drain closed and skimmer open. I can't get the pump to prime when I have it on waste, so no suction. It primes just fine when it's on filter setting. just had the sand changed in the filter, could that cause this problem?

Inyopools  Posted: 06/27/2016 12:58 PM  Inyo Product Specialist

mamdturner - You may have a small crack on the strainer cover. Try running the garden hose over the strainer cover while you are priming the pump. If your pump primes, inspect the cover and the strainer groove for cracks. To detect air leaks around the suction pipe connections, try smearing shaving cream around each connection. Air leaks will show up as pot holes in the shaving cream.

mamdturner  Posted: 06/25/2016 15:12 PM 

I have a Hayward TriStar pool pump for a water feature. The water feature stopped working. The pump will not hold a prime. The pump motor runs. The impeller is functioning properly. All screens and skimmer baskets are clear. I replaced the Strainer Cover O-Ring. Still no prime. I ran a water hose to fill up the Strainer Basket. The basket never filled up as water ran out the inflow pipe and never filled up after ten minutes. There are no detectable leaks. Am I missing something?