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hoffman 75 main vent

I want to replace the main vents on my 1 pipe steam system,
the current vents are original and I suspect not functioning properly they are mounted on tees with a 3/4
thread and reduced with couplings down to I would guess is 3/8
my local plumbing supply has Hoffman 75 main vents, is this a good replacement for the old ones and can I thread them directly to the tee. Thanx for any advice


  • Brad White_191
    Brad White_191 Member Posts: 252
    First know

    what your size and lengths of piping are. Once you have those volumes, figure a venting rate (time you want the mains to be fully vented and full of steam, usually one to three minutes). Then select a vent which will release that much air at very low pressures.

    In the alternate, get a wrench and an oven mitt.. remove the vent and time how long it takes for steam to get from the boiler to the venting nipple. That is the fastest vent you will ever have, the base-line to be approximated by a true vent in that location.

    If you have any doubts, you can take that one tapping you have and install a series of fittings that will allow you to add move vents of a type if the venting proves too slow for you.

    If the vents are original, I suspect that they are no longer functional. Vents do have a half-life...
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