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water leg

I have a 2 pipe system returning to a boiler feed pump.  The farthest steam main f&t trap has a water leg. The leg to get into the return line is approx.  20 inches higher than the f&t trap. Once into the return main it is gravity back to the bf receiver. The radiators on this farthest leg take a long time to heat up and the return cond line takes a long time just to get warm. I read in Dan's book that I need an air vent. He reccomends putting it on the second outlet port of the f&t trap. He talks about a Hoffman 75 being able to both vent the trapped air and break the vacuum when the steam condenses.  When I go to the Hoffman site to look at this vent it says non vacuum. Am I missing something here and is the the right solution for my problem.

Thanks for your help


  • Jamie Hall
    Jamie Hall Member Posts: 23,428
    It's confusing...

    The Hoffman 75 is non-vacuum, but what that means is that it will not hold a vacuum -- that is when the system pressure drops it will let air in to break the vacuum.  Which is exactly what you want.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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