Yeah I am running water through the pipes, and as long as the water stays water, then its fine. But some I have seen get so hot they turn the water into steam before it gets to the end stage. for winter it needs 4 or 5 stages and for summer just 1 or 2, so maybe a valve system, anyway K type looks the way to go
, that way I can automate the valves, Valves are another problem. I have spent ages at the recycle center and got loads of washing machine valves, but I am not sure how much heat they will take.