Air from one return jet and not the other

[PVpools]

Howdy all ! I have taken on a new pool to service and get up to snuff ! I know you guys like lots of details, but I'll make this short and will add to, with pics later .
Ok. it's an in ground pool, aprox. 20,000 gals. with a single speed 1.5 hp pump, sand filter and solar with no automation! The solar is controlled by one jandy valve and one gate valve. I do believe the main drain has been sealed off , or so it appears by that thing at the bottom. There seems to have been some retro=plumbing done at one time . Suction line , only one is 1.5 inch. It's all plumbed in 1.5 except the solar in in 2" I have never seen a skimmer like this one , it's larger !!! I would say the round cover is at least 14" in diameter and I can't see or feel the bottom. The very large debris screen sits up top and is the size of a pizza pan. I can't believe I stuck my arm in there and never felt the bottom !! The pump stays primed , but there is a lot of air in the basket ! The question at hand is , why are there noises up on the roof from the solar and loads of air returning via one return jet , but not the second ? Only 2 ! We are talking huge bubbles at a constant rate . Thanks !

 

[PVpools]

May I add , I think the most obvious answer regarding air from one and not the other would be it's first in the return plumbing path . But why so much air ? It's like a spa bubbler , lol . I have a hard time believing it's all from a suction leak. I was thinking bad solar vacuum valve or related . I shut off solar , no change ! Bad spider gasket in multi-port valve . I did notice the sight glass shoots out water in the back wash position . hum ???

 

[Bama Rambler]

There's a suction leak between the skimmer & the pump. When you find it, I bet all the issues go away. Air coming out of only one return is likely due to the way it's plumbed. The noise from the solar is due to the air. Most likely the erratic flow causes the vacuum relief valve sucking in air.

 

[PVpools]

Thank you Bama ! I need to remember air leaks upstream from pump. I still can't wait to get to the bottom ( literally ) of the skimmer . Why so deep ? Can't wait to see what's down there .