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Which main steam vent is better?

I need to change out a main steam vent in my home and found that there are two types of vents that my local hardware store carries (Hoffman #75, which sells for $60.00 and a smaller chrome cylinder type which sell for $20.00)

The location this this vent will be located on a pipe that is very close to the "Loop"

Maybe the 60.00 dollar vent is over kill. At this point just not sure!!


  • Steamhead
    Steamhead Member Posts: 16,710
    To answer this

    we need to know how long the steam main is, from the boiler to the point where the last radiator connection is. Also need to know what diameter the pipe is. This will tell us how much air needs to be vented, and whether the H-75 or the chromed one (possibly Hoffman #4A or one of the Taiwan-made ones) will have enough capacity to do the job.

    If the pipes have old insulation on them, measure its outside diameter (without disturbing the insulation, which is probably asbestos) and subtract 2-1/4 inches. This will likely give you the inside diameter of the pipe.

    If there are more steam mains in the system, it would be a good idea to measure them all and tell us what vents are on them.

    Main vent sizing is critical to good performance and efficiency. The money you spend here will save you lots of fuel.

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