air bubbles spa return

[foolio]

Hi - we just had a pool/spa built, 20,000; spa level with pool. shared variable speed jandy pump. venturi tube, no blower for spa.

I'm noticing, even at low speed, air bubbles coming out of 1 spa return only - is this most likely related to air from venturi effect or might I have a leak? air not coming out of any of the pool or other 3 spa returns...

 

[tsunami]

If you have a salt water generator, when the cell comes on, you will see air bubbles coming out of the nearest return.

 

[Bama Rambler]

It could be the venturi. While they don't work well at low flows it could be pulling a little air into the system. If you shut all the spa returns off does any air come out of the pool return(s)?