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Radiator NOT returning Condensate to Boiler.

Hey Y'all

One pipe steam system, has a vaporstat set at 10/4. This is a two family house and this system heats the 2nd and 3rd floors. All of the Rads get hot but the one of 2 on the same steam riser to the 3rd floor is holding it's condensate enough so that when it gets to a certain point is starts to leak out the radiator. Radiator is pitched properly and radiator valve is working properly (fully open, nothing broken inside of it. When I take off the vent you hear an audible vacuum release sound allowing air in and then the condensate returns to the boiler. Changing the vent hasn't helped it was a # 40 Hoffman to a Hoffman 1A. The steam riser originally fed the radiators to the 3rd floor was changed from the first floor to the 2nd floor steam main and goes up a chase from the basement to the 3rd floor to feed this radiator and another one also no issues with that radiator. been an ongoing problem and looking for an answer to this issue so I can get this dang house off of my service list.


  • nicholas bonham-carternicholas bonham-carter Member Posts: 8,358
    What other vents are on the system, including the mains?
    Could there be some Hoffman 76's (vacuum vents) on the mains?
    can you see how much vacuum there is in the system on the gauge?--NBC
  • John_88John_88 Member Posts: 8
    Gorton #2 and Hoffman # 75 venting on the mains, No vacuum vents in the system. The only place the vacuum is taking place is in this radiator.....
  • John_88John_88 Member Posts: 8
    edited January 2016
    On the rads, 8 others Hoffman 40's
  • JUGHNEJUGHNE Member Posts: 7,910
    Had this issue with 3rd floor rads. These had RAV thermostatic air vents without vacuum breakers, I know this is not what you have but for these air vents to work properly the system had to cycle almost down to 0 PSI for them to open at all. Maybe you just need a separate vac bkr on that particular rad. They were sold separately for the old RAV vents. FWIW
  • John_88John_88 Member Posts: 8
    Just looking for some ideas to what it could be
  • RJ_4RJ_4 Member Posts: 484
    I have had similar problems, found that the disc on the radiator valve had deteriorated and collapsed inside the valve, allowing steam into radiator but not allowing condensate out. Also check my post on Feb. 2012 auto control of 1 pipe steam

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