Air leak? Cavitation??

[CrystalRiver]

I constantly (except once) have air in the pump. Not a lot, no visible bubbles coming from the return but it may be causing my foam. I can also hear some air in the filter. Everything seems to be functioning so I haven't worried about it.

When I added the vacuum plate and hose, filter pressure dropped from 13 to 10, and the pump basket emptied about half way. I could see the full stream of water entering the pump (stream was not submerged). Still no visible bubbles from the return. I vacuumed briefly and things seemed stable, but I was wary and didn't continue more than a couple of minutes.

When I shut the pump off, it instantly mostly refilled with water. There was maybe a bit more air than before vacuuming, but less than when I remove and replace the lid to clean the basket.

Thoughts?

 

[Texas Splash]

Whenever I connect my vacuum, the pump water level always drops. My hoses and connections are fine, and my hose drops directly into the skimmer hole (no skimmer plate required), and still it drops. I just chalk it up to the mechanics of it all, pulling water through a slightly different size hose and vacuum head which is effecting water flow when not in use. Like you, as long as the pump is still maintaining prime I don't worry about it too much. But maybe you can experiment with different vacuum set-ups (hoses, head sizes, etc) to see if that makes a difference? If you have other parts laying around.

You mentioned foam though which sounds like a chemical issue more than anything else. Are you sure to use plain/regular bleach or liquid chlorine? Nothing splashless or scented?

 

[CrystalRiver]

I'm using HTH Liquid Chlorinator. I'm chalking the foam up to high organic load for now - I'm up to 16 inches of visibility. It's come a long way, but there's a long way to go, too.

 

[CrystalRiver]

Definitely an air leak. I was able to see (while vacuuming) small air bubbles coming from the return, and ended up losing prime. The filter basket housing is cracked due to previous non-winterization. In normal use, it has a very slow drip, but doesn't lose prime. I guess the additional negative pressure caused by the resistance of the vacuum hose is enough to draw too much air through the crack.

At least now I know the cause.