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Main steam vent

100 year old system.
1 pipe steam.
Original system did not have a main steam vent.
Do I need one now?
What would the advantage be?

DC Kingston NY


  • BobCBobC Posts: 4,965Member
    Old coal fired systems were always hot so they only suffered the lack of main vents sporadically. Modern on/off oil and gas fired steam boilers have to expel air a dozen or more times a day in cold weather.

    Money is being sent up the chimney whenever a boiler is firing. If you don't mind paying money to squeeze the air out of the radiator vents then leave it like it is. If you want to save money and allow the system to work better, install a main vent on each steam main and make it a great big one!

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • FredFred Posts: 7,874Member
    How long is the main(s)? If more than one main, each should be vented to move air out of them quickly and allow the steam to go where it is needed (to heat the living space) and allow you to balance all of those spaces properly. As Bob said, It's money going up the flue without good main venting.
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