Question about venting steam radiator?

I have a vertical steam radiator, steam inlet at the top and water drain at the bottom. See link for a picture, but rotate it. I have had 3 different plumbers give me 3 different methods to install a vent. Right now I have a "trap" at the bottom, and it started leaking after a few years. Another plumber said the vent is incorrect, and it should be at the top. Yet another said a proper vent at the bottom. What to do? what kind of vent? thanks


The radiator manufacturer says no vents are needed in a 2 pipe steam heat system. Insists that is true. I also checked with a leading manufacturer of vents, and they could not offer any opinion.

rotate first link 90º. Second link is as is.

problem is leaking vent/trap.

2 Answers

  • 7 years ago
    Favorite Answer

    A trap and a vent serve two completely different purposes.

    The trap allows condensated steam (water) to return to the boiler, while preventing the steam from passing through. It must be located at the very lowest point on the radiator. If any water is trapped in the radiator you can have steam hammer. A trap will also let air out of the radiator when the steam is allowed in. This is why no vent is necessary on a two pipe system like yours. However, if the manufacturer recommends one, then you need one.

    Vents are only required on one pipe steam systems. The vent allows the air that is inside the radiator to be forced out so that the steam can occupy the space. The vent is a valve that allows air to leave, but closes when the steam has arrived. The vent is usually located at the far side of the radiator from the steam/condensate pipe, and usually but not always, near the top. This is so the steam will pass through all the tubes before arriving at the vent, forcing out most all the air.

    . All vents and traps have rules about how they are oriented. I could not tell from your photo what the top was, you said it was a vertical radiator, but rotate the photo 90 degrees. That would make it a horizontal radiator.

    You have not stated what your problem is with the radiator. If it is not producing enough heat, it is more likely the trap is improperly selected or has failed, or you have the incorrect steam pressure.

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  • 7 years ago

    I would put the vent on the side of the radiator near the outlet. You should consult with the radiator manufacturer or a heating engineer to get it right the first time.

    Source(s): Old guy
      Lv 5
      7 years agoReport

      I see the amended question is about a leaking trap. If he will post another question with more details, I am sure I can answer any question related to steam systems.

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