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quick main vent questions

SBoston Member Posts: 61

At the end of my main line there is a return that starts dry and drops straight down collecting all the other returns (like plenum) and then turns into a wet return and heads under ground and back to my boiler. My question is,

Since I have a spider web of mains that head all over the basement, would it be permissible to drill and the dry tap the dry portion of the return (on the side), under all the other dry returns and install a main vent? This way I am able to use 1 or 2 main vents instead of 8. Would this work?

2nd question; why is a Gordon #2 a 1/3 the price of a Hoffman 75? Is a Hoffman main vent better then the Gordon? </span>


  • Crossover?

    I think there maybe a problem with your plenum situation as I would think the dry returns would crossfeed. Normally they are joined in the wet return (under water as the water acts as a trap)  or have to be trapped. I'm sure Steamhead or one of the pros can give you a better answer on this.

     A Gorton #2 has over twice the venting capacity of a Hoffman #75. In my limited homeowner experience they both manufacture good vents.

    - Rod
  • Jamie Hall
    Jamie Hall Member Posts: 21,541
    Er... uh... a picture?

    Maybe a picture would help?  Or a sketch?

    But a vent, to be effective, needs to be beyond the last radiator riser takeoff.  However, since it is venting air, it doesn't have to be at the end of the line (in fact, for protection of the vent, it is common for it to be a short distance before the end of the line).

    I take it there is no independent dry return picking up the other returns and going back, dry, to the boiler and then dropping down?  Some systems are piped that way, some aren't.

    But to get back to what I think you said, the vent or vents at the end does not have to be below all the other dry returns; it could be anywhere so long as it is after the last radiator takeoff on any of the lines.  In fact, you don't want it too low: keep in mind that when pressure builds in the boiler, the water level in that vertical pipe is going to rise -- and the last thing you want is for the vent to go under water.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SBoston
    SBoston Member Posts: 61
    edited October 2009
    main vents

    Attached is a piping layout of my boiler. The black lines represent the mains and risers. The red indicates the dry returns (they are very low that run against the basement walls picking up the each riser) the blue shows were they go from a wet return to a dry return.

    Since I have so many long risers and mains that it would be best to install two main vents. Both of them just before both dry returns turn into wet returns.

  • Jamie Hall
    Jamie Hall Member Posts: 21,541

    I don't find the attachment (that may be just me), but the idea of two vents on the dry returns just before they switch to wet sounds appropriate.  As I noted earlier, make darn sure that the dry return is high enough to stay dry where the vent is installed -- you should have at least 18 inches to 2 feet above the boiler water line, as a minimum, and be running very low pressure.  Otherwise you'll wreck the nice new vents...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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