Do you have a salt chlorine generator? They sometimes produce bubbles. It is actually hydrogen gas - a byproduct of making chlorine.

landa mac- Yes I do have a salt generator. Maybe that is why I only see the bubbles once in awhile.
Thank you for the info.

Luvh20

Crank the pump up to a high speed. Turn it off and watch one area. The pipe that screws into the front of the pump. If you see it eject a bit of water, then you have found your source. do the same for the pump lid and the valve in front if you have one. If there is an actuator on the valve, you should pull it off. You're looking for water at the handle stem in the cap or an sound of air at that point when the pump goes off. you may have bad stem o-rings.

Its perfectly normal to see Hydrogen bubbles coming from the return with a SWCG. You probably may also notice that the returns closer to the equipment bubble more than the ones further away.

barco- yes it seems to only come from the return closer to the equipment. And it's not constant, it comes and goes.

Depending on the output level you set your SCG to - it will only produce chlorine part of every hour of use. All SCG's work the same way - on an hour basis. A 50% output setting generally means the chlorinator is producing chlorine 50% of the hour.