Pump not priming solved! Cause: LEAK ON THE RETURN SIDE

Apr 6, 2019
23
California
I was told a return side leak could never cause a pump to not prime. I tried everything else until today when I finally fixed it!

Short story:
My basket was full of air. The skimmer was pulling in water very slowly. Despite the pressure being high (30 PSI when running at 3300 RPM) on the filter gauge, water would just dribble out of the pressure relief valve.
  • I replaced the strainer o-ring. No change.
  • I put silicone caulk on all exposed plumbing connections in case there was a tiny leak. No change.
  • I put silicone lube on the gasket for the two drain plugs on the pump. Now water would shoot out the pressure relief valve when I opened it. Other than that, no change.
  • I put silicone lube on the gasket for the union fitting in front of the pump. No change.
I had noticed the main o-ring on my filter was worn, but I was told by many people that water would leak if there was an issue and also the return side of the system doesn't affect the pump priming.

Having exhausted everything else aside from taking apart the pump and digging up the plumbing to look for pipes, and because I figured I would have to change it soon anyway, I gave it a go and replaced it.

Once I did that, my basket filled up to the top with water. My skimmer was pulling water so fast I had a small vortex like before when the water level was a little low.

My theory is that water goes into my filter at an inlet above the o-ring seal, and exits the filter at an outlet below the o-ring. Somehow the water passing the o-ring causes the filter to actually suck air in. This incoming air pressure constantly fights the incoming water pressure, and because of this the basket and filter cannot fill completely with water.

Anyways, I am happy I finally fixed this issue and I thought I would write this post in case others faced the same issue.

Also, about 6 months prior the basket level dropped to about 50%. At the same time I replaced the slide part of the slide valve on my filter. It had a tiny leak and water would come out sometimes, not to mention the entire handle broke and I could not backwash. After replacing this I did notice basket water level raised to about 75%. I mentioned this to the local pool nerd at the store, but he dismissed it as having anything to do with the basket water level.
 

JamesW

TFP Expert
Mar 2, 2011
14,562
The main filter O-ring will have no effect on the pump priming. It might seem related, but it's not.

You might have an issue with the grids being dirty or maybe a problem with the slide valve.

If you don't get good flow from the air relief valve, it's probably clogged with debris.

Light debris, like styrofoam, grass etc floats on top of the water inside the filter and gets jammed in the air relief valve when you open it to let the air out.
 
Apr 6, 2019
23
California
The main filter O-ring will have no effect on the pump priming. It might seem related, but it's not.

You might have an issue with the grids being dirty or maybe a problem with the slide valve.

If you don't get good flow from the air relief valve, it's probably clogged with debris.

Light debris, like styrofoam, grass etc floats on top of the water inside the filter and gets jammed in the air relief valve when you open it to let the air out.
Yeah. That's what was everyone told me on this forum. It makes sense in general that the return side has no effect, but perhaps in certain situations it can affect it.

All the changes I listed I did weeks apart. I could never solve this problem for months.

The last change, changing the o-ring on the filter was the last thing I did. I made that one single change and nothing else last week and it had the positive effect.

There is no doubt that was the cause.

Also, when I first got the pool, the pump worked fine. It wasn't until I cleaned the filter by taking it apart and putting it back didn't the problems start. The o-ring was totally pancaked and when I took the filter apart it disturbed the seal and I wasn't able to properly seal it again until I got the new o-ring.
 
Apr 6, 2019
23
California
Yeah it did however it was never able to rid itself of the air. I don't have a check valve on the auction side so I can never prime the pump basket with water before starting the pump. Now it can rid itself of the air during when the pump starts with its priming program (3400 rpm). Before it was not able to do that.
 

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