Circulation Cycles Up and Down

[ralber]

Anybody have this problem before? When I turn on the main pool pump the water flows fine through my skimmer and into my Pentair cartridge filter. When the filter hits 10 lbs of pressure the flow abruptly stops and pressure quickly falls to 0. Then the pump slowly builds up to 10 lbs of pressure again (it takes about 20 seconds) and then abruptly falls to 0. This cycle repeats indefinitely. My normal filter pressure is about 15 lbs. At the skimmer I can see the water rush down the holes when the pressure is building, then stop flowing entirely after the pressure in the filter drops to 0.

My 1 hp Sta-rite motor and pump unit is about 6 years old but makes the same sound it did last week when everything was working fine. I can't find any air leaks anywhere. I replaced the filter cartridges recently but when this started I removed them and ran the filter without cartridges for a few minutes to see if the same cycling problem persisted. It did.

Should I take apart the pump impeller to look for debris? Or should I look for a problem elsewhere?

Thanks!

 

[duraleigh]

Welcome to the forum :-D

At the skimmer I can see the water rush down the holes

Is there a chance that the water is too low in the pool and the skimmer is actually forming a vortex and sucking air?

If so, the pump will drop it's prime and the cycle will repeat over and over.

The water level should be approx 1/2 way up in the skimmer throat.

 

[bk406]

Check the little door on the skimmmer (it's called a weir). If that is stuck, it can cause what you describe.

 

[ralber]

Thanks for the quick response. I suspected the problem was caused by the skimmer not working properly so I checked it right away. The water looked to be at the correct level and the weir was swinging free, so I figured that wasn't the problem. However, my wife added some water this morning and the level is a little above the normal level and, by gosh, the system has been working fine all afternoon. The pressure is steady at 15 lb. and water is swirling around consistently in the skimmer. I guess the water level was probably the culprit.

But I think there's more I need to know about air bubbles or pump priming, or something, because when it seems like the water doesn't flow smoothly through the debris trap just in front of the pump (with the clear plastic top) when I first turn on the pump. Is there ever a need to prime the pump and if so, how does one do that?

Thanks!

 

[duraleigh]

the water doesn't flow smoothly through the debris trap just in front of the pump (with the clear plastic top)

People call it a bunch of different things but what I've always heard is correct is "pump strainer basket"

The pump is self priming. That air and gurgling when you start it up is the pump fighting to get the air out of the system. If your circulation is working properly, the pump will force out all of the air and you will see nothing but water in the pump strainer basket. It can fool you and almost look empty. Once the air is purged from the system, the pump is then "primed".

 

[Durk]

I would check your pump trap cover and lube your cover O-ring with Teflon lube. If the cover is allowing air in, it can cause or contribute to the problem.