Suction Air Leak & Coming Freeze

[wgmamc11]

Hi All,
3 months into a new house with a pool, and I have constant bubbles in the pump lid and coming out of the returns. I can't find the leak and we have 5 days with lows in the 20s coming. Should I be worried about freeze w/ freeze protection running and the pump still moving water?
So far I've tried:
- Pump lid gasket cleaned & lubed. No visible damage to gasket.
- Put soap suds over all suction side components and PVC joints. No obvious air movement.
- Run garden hose over components. No change in bubbles in pump.
- Filled pump with garden hose & restarted. No bubbles until I turned pump off and back on. Makes me think air is being sucked in when pump is turned off but not being expelled when turned back on.
Any recommendations on what to try next?
Thanks!

 

[HermanTX]

You have a variable speed pump. Does the bubbles occur only at low speed? If you run pump at full speed do the bubbles disappear? Also, a SWCG will produce some bubbles - especially at low pump speed.

 

[wgmamc11]

My old AquaLine controller cannot control speed, so pump really only runs at 2800rpm. I just tried it at 1550rpm and there are no bubbles, but the pump does not fill up and water barely drips over the spillover. My SWCG is turned off right now, so it's not that.