I just figured something out - but still not there yet.

When I partially close (restrict) water flow to the roof and send some though the bypass -- I eliminate the air bubbles - but I'm sending some water to the roof and some water through the bypass.

So it appears when I send full water pressure up - it creates a vacuum and lets air in.

This is temporarily OK -- but it wont work with the automated controller.

How do I solve this problem?

BTW -- heating an IG pool.
Thanks