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B&J Big Mouth leaking steam

jeffg Member Posts: 6
We are reviving the old 1 pipe system in our 1910 house, that we bought this year; so far we have replaced the old coal/oil steel-tube with a new gas-fired Smith boiler. I replaced the old Trane main vent at the end of the dry return with two B&J's mounted on a 3/4" branch. The vents worked great for about 2 weeks; the issue is now one of the vents works perfectly, but sometimes the other vent will leak steam. I took it off and opened it up, but it is clean inside, the o-ring is in good shape, and it sounds like it has liquid inside the bulb. I have the cut-in set at .5 and the cutout set at 1; normally pressure is .5, sometimes it will creep up to 1.5, when it is really cold and running hard. Any ideas why one vent will vent out steam while the other closes normally?


  • Sailah
    Sailah Member Posts: 826

    It should leak steam at all. If it has liquid in the disc, we can (almost) eliminate that as the cause. The only other real possibility is that something is obstruction seat/plug interface. Debris/rust can do it, that's why we tell people to put them as high as possible.

    If it's within your Amazon return window, have them send you a new one and B&J will get the old one back and test to see if they can figure it out. If it's outside the window you can contact them directly to have them ship you a new one. I was just at factory last week, highly suggest using Amazon if possible as they are getting ready for AHR Expo and really busy.

    Peter Owens
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    edited January 2018
    Are there crossover traps on this system? If so, then they should be the first line of Defence against steam going where it should not. Check their condition first.—NBC
  • jeffg
    jeffg Member Posts: 6
    @NBC - there arent any crossover traps; its just a 1 pipe system