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Steam Boiler

I replaced an sectional boiler that was installed in 1926. When we started the tearing out when we found one of the return pipes (1 1/2") running into the brick flue. When we removed the metal flue piping from the boiler and look up into the flue liner we found the return pipe with a 90 degree ell looking up and then back down with an assortment of nipples and elbows. This made the return line open in the chimney. The line was ran up high near the ceiling above the boiler and was tee in above the draining part of the return line. It was venting the return line up into the chimney but it had no way of traping steam or pressure. I have never seen this done on boiler piping before, does anyone know why this was done?


  • Al Letellier_9
    Al Letellier_9 Member Posts: 929
    piping in chimney

    Sounds like an old vapor regulator system where the dry returns were vented up the chimney.The piping rose high enough to offset system pressure and allowed air to vent out without losing any steam. See the two-pipe section in Dan's book (Lost Art....)

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  • Christian Egli_2
    Christian Egli_2 Member Posts: 812
    A vented air hole

    It provided free suction draught to exhaust the air from your two pipe system, just like a vacuum pump would (although the vacuum pump is more powerful and not free).

    Steam was not supposed to ever get there, as you know, the radiator traps stops the steam from entering the return lines. And to stop any escaped steam, this vent line probably travelled through one open radiator hung on the ceiling.

    How are you repiping the whole thing? Are all the radiator traps functioning? How is your B dimension?

    And you thought it was for heating the birds!
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