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Full port ball valve

Want to add a ball valve as a king valve on my main 2inch line after my header but a full port 2 inch ball valve opening is almost a half inch smaller than the 2 inch pipe opening. Is this ok or should I bush it up to2 1/2 and then back down to 2 inch.

My other question is where should the main vent be. I have a parallel flow gravity one pipe system with a dry return. The vent is presently at the end of the dry return before going into the wet return back to the boiler. There is no main vent on the end of the main but there is pipe about a foot before the very end of the main not going to a radiator that is capped. Maybe someone removed a vent from that location? Should there be a vent there also?

Much appreciated


  • Rod
    Rod Posts: 2,067
    Full Port Ball Valve

    Hi- It doesn't sound like you are looking at a "full port" ball valve. Attached is a spec sheet for Hammond valves and you can see that the ball opening is close to or slightly greater than the connecting pipe size.

    Main Vents-  The main vent(s) will work fine at the end of the the Dry Return. If you can give us the length of the steam main and pipe size we can calculate how much main venting you need. 

    - Rod
  • Peteys
    Peteys Member Posts: 79
    edited September 2013
    Full port ball valve


    No specs, but I measured and it is indeed not 2 1/4 inches. More like 1 3/4.

    2 inch pipe is about 2 1/4 diameter, I believe.

    One of the mains is about 60 feet of 2 inch. The dry return is a little smaller, 1 1/2 maybe.

    And the dry return is another 40feet. That's where the vent is presently.

    Thanks Rod
  • Rod
    Rod Posts: 2,067
    Main Vents

    Hi-  2 inch pipe has an outside diameter of 2.375 inches.

    Main Venting -

    A  2 inch pipe contains .023 cu.ft. of air per lineal foot.

    A  60 ft. - 2 inch Main contains .023 x 60 = 1.38 cu ft.

    A 1 1/2 inch pipe contains .014 cu.ft of air per lineal foot.

    A 40 ft  -1 1/2 inch Dry Return contains .014 x 40 = .56 cu.ft

    Main Vents

    A Gorton #1 @ 1 oz. pressure vents .330 cu.ft per min.

    A Gorton # 2 @ 1 oz. pressure vents 1.10 cu.ft per min.

    I'd use one Gorton #2 at the end of the Dry Return - Unlike radiator vents, you can't have too much venting capacity on the main vents.

    - Rod
  • SWEI
    SWEI Member Posts: 7,356
    Just to be clear

    Full port means pipe ID, not thread of valve ID.
  • Peteys
    Peteys Member Posts: 79
    Full port

    So do you think I should be ok with that valve? I measured again and it's a 3/8inch difference from the inside of a 2 inch pipe to the insideopening of the ball valve. 2 1/8 to 1 3/4.
  • Rod
    Rod Posts: 2,067
    "Standard " vs "Full Port"

    It sounds like what you have is what is known as a "Standard Ball Valve". In the "Standard Ball Valve", the port opening (the hole in the ball) is about one pipe size smaller than the pipe size that fits the ball valve's threads.


    On a "Full Port Ball Valve", the port opening (the hole in the ball) is, as SWEI mentioned, the same size as the ID of the pipe.   2 inch pipe has a 2 inch ID so a "FullPort" 2 inch valve would have a 2 inch diameter port in the ball. (Pipe ID = Ball ID = Full Port)

    As you generally don't want restrictions in steam pipes, I'd definitely use a "Full Port" ball valve.

    - Rod
  • Peteys
    Peteys Member Posts: 79

    Thanks Rod, that makes sense and that's what I'd like. Don't know why the ball valve I bought isn't like that, as its listed as full port. Guess ill buy the Hammond .
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,849
    I'd return it.

    It could be an honest mistake (e.g. something got put in the wrong bin) or else they figure that most people aren't going to measure the port, but full-port valves cost more than standard port valves, so when you pay for one you should get one. It's not just a matter of getting your due. If they think they can get away with selling cheaper parts for more by misrepresenting them, they'll keep doing it, and if it was just a mistake, maybe they'll be more careful.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
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