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Boiler water Supply

Hey Everyone,

Question :
I have a combo steam/hot-water boiler in my home. The Hot water side only feeds 2 radiators on the extension portion of my home. Do I keep the main water feed valve open or closed?
**I Brielfy turned it on to fill system.

***Before it enters the boiler, it passes through a pressure reducing valve and relief valve....

*** Also, there’s no automatic shut off if no water is passing through return pump. The site glass is only for the steam side of the boiler hence would kick off from the low water cut off.

I honestly can’t remember if I shut this supply line off during the summer or not.

Thank you in advance.


  • If it is a steam system with a hot water zone(s) you only want to be adding water to bring it up to the water line. If you have an automatic feeder, leave the water turned on to the feeder so it can fill when needed. If it was manual fill and water was left on it would fill the whole system and squirt water from the radiator air vents and/or lift the 15 psi safety valve.
    EBEBRATT-Ed Member Posts: 9,630
    Take some pictures and post so we can help