I think I have an air leak somewhere, but I'm not quite sure. My pool and equipment are about 2 1/2 years old. About a month ago, I noticed one morning that shortly after our pump turned on that it sounded like it was priming itself.
I went and looked and it was nearly full but was still filling itself back up with water. Since then I've noticed that every time the pump is on there's some air in there (pump basket area) sloshing around with the water. Normally it was always completely full with water and you couldn't see water or air moving around in there at all (maybe a tiny bubble or two here and there, but that's it).
The pressure gauge on top of the filter is reading normal. Tonight after the pump had been off for a while I went out and looked at it, and the water level in the pump had dropped down to just below the inlet pipe. So I took the lid off and cleaned the basket, then turned on the pump and let it self-prime. Again, it filled, but not completely as it used to. There was some air at the top that never would purge completely.
I noticed also that, after the pump has been running for a while, if I open up the filter air relief valve some air bleeds out for a moment before it's purely water squirting out. I'll close the valve, then if I reopen it a minute later, again some air bleeds out before it's all water.
Lastly, after I shut off the pump tonight, I stood there and observed it for a while and sure enough, water drained out of the pump very slowly until it was at the level of the inlet pipe. Every several seconds an air bubble would appear and a little more water would drain out. It looks like it's draining back out into the inlet pipe.
It definitely seems that something is wrong. What should I be checking out to try and diagnose this?