VS Pump taking in air at low speeds

pcm2a · Jun 1, 2020

On my new VS pump, if I run it at 3100 or 3450 there are no bubbles in the pumps viewport. Then I change to a lower speed, 2250 or 2500. Over the course of 8 hours I noticed that there slowly is more and more air in there. After 8 hours the water level is an inch down from the top. I can turn the speed back up and it fills back up in 30 seconds. I didn't notice this previously because I ran a schedule like fast->slow->fast->slow. The pool is full of water and it is not sucking air into the skimmer.

I assume that this is not normal operation? Where do I start with finding out how the air is getting in?

If there is a place where it is taking on air, how does the air get in at slow speeds but not fast speeds?

pcm2a · Jun 1, 2020

I found a great post on here Pentair Variable Speed Pump losing prime at lower speeds (adding it so I can find it later). I'm going to try the ideas in there. Not the same pump but the same symptoms.

Jimrahbe · Jun 1, 2020

2a,

It is normal for there to be a little air under the lid at low speed.. But.. the bubble should not get larger and larger as time goes on.

I suspect that you have a leak right at the O-Ring under the pump lid.. When you run the pump at a higher RPM, the lid actually gets sucked down tighter against the O-Ring.. at a low RPM, not so much. Make sure the O-Ring is well lubed.

I have also noticed that the dirtier my filter gets, the larger the bubble seems to get.

Since you have an automation system, one fix is to schedule the pump to run at a faster speed a few times a day for 15 minutes or so.

Thanks,

Jim R.

pcm2a · Jun 6, 2020

I took the lid off and the installer did not put any magic lube on the seal. It was kind of hard to get a fat finger down in there but I greased it up pretty good. Now at 2500rpm after 4 hours there is a tiny bubble and after 8 it's a bit bigger. Doesn't seem to be affecting the performance. Overnight, with the pump off, the bubble does not get bigger.

I ran it like this for a few days and it has been consistent. Yesterday in the afternoon I tried kicking it up to 3100 for a few minutes and the bubble was gone. I'll fiddle with the speeds just to see what the lowest speed is that has no bubble. I might also try a lower speed to see if the bubble is any bigger.

SDor · Jun 6, 2020

I have a variable speed pump and see similar behavior. Long slow period or especially dirty filter, and I get a bigger bubble in my filter. Stays primed when shut off overnight. I guess I will try some magic lube on the pump gasket, but it doesn't seem to really hurt anything so I've been ignoring it for now.

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VS Pump taking in air at low speeds

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