Mike, are you still trying to blow yourself up?

Seriously take my word for it, it is hydrogen. I think there is definitely a leak and that has to be fixed. If air is coming, the best test I know, is to open the vent on the filter, and if lots of air comes out, then you have an air leak. That would be a big problem as you would be mixing hydrogen and oxygen with the possibility of blowing the cell or piping downstream apart. Your only recourse would be to shut off the SWC and use bleach until you find and fix the leak. That is why all piping and equipment on the suction side of the pump has to be airtight.

If it is only for about two seconds or so, the air leak is minimal, and could come from air dissolved in the water. The bubbles would then have to be hydrogen.

Hope this helps.

Pat