Hello - let me first say thanks to this community. I'm new to pool ownership and put one in a couple of months ago (details in the signature). I found this site and spent a few hours learning as much as I could even before the pool was complete. Having a bit of a background in chemistry, I immediately took to the testing and logging. It's only logical.
My question comes from my effort in tracking down a leak. When the pool was complete, the temps were in the 100* area and so adding/replacing water seemed normal. After a break in the heat and some rain fell, I started questioning the water replenishment and paying close attention to everything. The PB is involved - so I'm not alone in tracking it down but something I noticed seems odd to me. One return occasionally spits some bubbles. There are 4 total returns in the pool and 1 is dedicated to the Polaris (which gets it's feed from the pressure side of the filter - 1st T after the SWG). The other three returns are fed from 2 pipes split after the Polaris T. One jet is on it's own 2" pipe and the other 2 are split from the other 2" pipe. I hope that makes sense. The return that intermittently bubbles air is a jet from the split. The other on that split does not spit air nor does the jet that is on it's own pipe. By intermittent I mean I see them at times - observed for as much as 30 minutes at a time and then other times I don't see them at all (pump running of course). There's no air in the pump bowl and no air from other returns including the Polaris.
What would cause that? I generally think that a pressure side line would leak water out of the pipe when under pressure and not pull air in. The PB doesn't seem to know and wants to continue looking for the water leak (1/2" daily) in the liner.