Well, my solar heating system is up and running and seems to be working ok. I had to replace my 3/4hp pump, so I put in a Pentair Intelliflo; amazing pump. I am waiting for a flow meter to arrive to I can test the flow into the solar collectors, but in the meantime I have a question. There are no leaks on the roof from any of the connections, unions, etc., but I am getting air bubbles from the return in the pool. Also, I can hear the water gurgling in the hot return pipe on the roof. Any idea why? There is plenty of flow on the cold supply to the roof (you can feel it in the pipe), but have much less flow and gurgling on the hot side. Is that just the way it is after coming out of the coil collectors?