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Boiling Water In Vertical Pipes
I have a hydronic heating system. (Baseboard radiators with copper pipes and aluminum fins). I can feel and hear water boiling in the vertical pipes going from the 2nd floor headed to the 3rd floor of the house. Its an old house and previous owners have painted over the vertical pipes. I have lowered the aquastat to the lowest setting and i can still feel it boiling. Can anybody help me with this? Is it dangerous and if so, how can i fix it. Thank you.