I wonder what ratio of glycol? Anyone who has tried to pump 100% in a system know how bad it foams. My original confusion was I thought he said he was running Dom and space but on a closer look its obviously not. With that said the water boiling sure sounds likely, I don't have the manual so I can't say for sure on the piping but fire control had that solved. I bet pump size could be a factor with the high pressure drop, or boiler pressure.