Pool circulates water great for a few hours then slowly stops circulation - pump still running

[Jrz_dad]

I have an older fiberglass pool system - hawyard 2hp pump (newly purchased and installed last year). the system has been working fine until we had a gasket issue with the chlorinator. Fixed the issue and now the system will pump water great for a few hours then it just stops pumping (almost like there is a blockage - but there is NONE that I can see). The baskets are clear...the filter has been backwashed as well.

its like once I stop the motor, open the top to the pump basket to check contents, then reinstall the lid, it will start pumping again for a few hours then the process starts all over...any advice on where the problem might be? Thanks!!

[Denniswiseman]

Did you have a 2hp pump before
It seems like there is air getting in the system
Check the water level is 1/2 to 2/3 up the skimmer door and that the water is flowing without sucking in air
When it stops next time look in the pump basket and see if there is air in it because when you check it you are releasing the air

[Jrz_dad]

Yes, we have had a 2hp pump before - there is plenty of water in the pool & the pump is not sucking air thru the skimmer - I will check the pump basket and report back - thank you!!! JV

[Teapot]

Pump above the water level?

[Jrz_dad]

no - pump is below water level. I did a closer exam based on Denniswiseman input above...i started by replacing the pump basket strainer lid gasket even thou the old gasket looked fine. So far, its been a couple days and a few cycles of circulation - its working as designed now. Perhaps the old gasket was the issue and it wasnt obvious as to any damage to it? Anyway, i will keep an eye on things and report back in a couple days...THANK YOU EVERYONE who responded !! I appreciate the help alot!!!!

[Denniswiseman]

no - pump is below water level. I did a closer exam based on Denniswiseman input above...i started by replacing the pump basket strainer lid gasket even thou the old gasket looked fine. So far, its been a couple days and a few cycles of circulation - its working as designed now. Perhaps the old gasket was the issue and it wasnt obvious as to any damage to it? Anyway, i will keep an eye on things and report back in a couple days...THANK YOU EVERYONE who responded !! I appreciate the help alot!!!!

That is generally the first place to check for air getting into the pump basket. Lubricating it with silicone grease will do the same job

[DThela]

Why should pump elevation matter as long as its a foot or two?

[DThela]

Mine has no air, primes good runs good then builds up a vacuum? Lines are clear filter backwashed. How could I have a vacuum? Runs for an hour then half pump basket of water and have to vent to open cover on filter!

[Denniswiseman]

Mine has no air, primes good runs good then builds up a vacuum? Lines are clear filter backwashed. How could I have a vacuum? Runs for an hour then half pump basket of water and have to vent to open cover on filter!

If you are getting air in the pump basket then you have a suction side air leak. When you vacuum your pool you are putting an extra load on the suction side which will suck in more air
Common areas are pump basket "O" ring, pump drain plugs and pump inlet union
A small crack may not leak water but could suck in air

[DThela]

Yes I know! I'm just taking in water through the skimmer so if the skimmer if full and flowing and there are NO bubbles in the pump how could there be a vacuum after I turn off the pump? Wouldn't it just backflow through the skimmer? There are no air leaks. if there was an air leak I wouldn't get a vacuum buildup in the pump basket. I have to pry the pump cover up to get it off!

[DThela]

And it happens even when I'm not vacuuming, just open skimmer

[Teapot]

Why should pump elevation matter as long as its a foot or two?

Simply because with one below the water line you are flooding the pump. Above the waterline you are drawing harder so more likely to get air leaks.

[DThela]

Ok got it , but thats not the difference in pressure I'm getting. It's like the skimmer line is plugged solid. But yet when I force the pump cover off the water flows back to the skimmer. The only thing I could think it acts like is a checkvalve. Skimer line open to pump if I shut the pump off it should just flow back through the skimmer. Don't mean to say it many times different ways but everybody tells me air leak and there isn't any. I appreciate the responses I really do but being an engineer I understand how the system works and should work but this makes no scientific sense LOLOL. We even went as far as "gooping' all the fittings to prove to a "pool guy" there were no leaks and he scratched his head and left! LOLO

[Teapot]

Hate to state it but it has to be a suction side air leak, albeit tiny. I had a customer with similar and similar response. Eventually that was a tiny crack in the pump filter lid that could only be seen at an angle under electric light in the kitchen with a magnifying glass. Because I am on my phone I can't see your pool pump/filter spec and we are only on a pc not there in person.

[DThela]

It seems the 1hp pump is too small. But when you first turn on the pump it's empty and full of air and the pump sucks the air out to prime. why should a tiny air leak affect it and only after an hour of running? It primes up and runs with only a little bubble in the cover