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No main vent? How to install one

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rjp8292
rjp8292 Member Posts: 10
I have a one pipe steam system. One main pitched away from boiler that loops into a return back to the boiler. My question is why is there no main vent? Can I put one in if I drill and tap the 2"elbow at the end of the main or do I have to mess with the 100 year old pipes and install a union?

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  • rjp8292
    rjp8292 Member Posts: 10
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    Here is the end of the main.
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
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    If you can get at it, you can drill and tap the 2" elbow.

    Where does that branch go that comes off the top of the main just before the drop? Is that also 2"?
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • rjp8292
    rjp8292 Member Posts: 10
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    That's the last riser to the second floor master bedroom and the first floor living room radiator. Is not 2" it's 1.5" What is the largest hole I can drill into the elbow without compromising it?
  • JUGHNE
    JUGHNE Member Posts: 11,110
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    It may be better to avoid the elbow end of main of possible water hammer and drill about 6" below the elbow into the vertical drop.
    1/4" IPS tapping will handle one G2 air vent.....you could do 2 tappings if needed.
  • rjp8292
    rjp8292 Member Posts: 10
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    Are you saying I would cause water hammer by doing it in The elbow or existing water hammer would be an issue?
  • Fizz
    Fizz Member Posts: 547
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    Are you having any issues with your system now?
  • Gsmith
    Gsmith Member Posts: 433
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    Jughne's comment was meant to say that if your tap the elbow and put the vent there that any water pushed along in the steam main might wind up in the vent. If you put the vent on the downward leg after the elbow there is less likelihood of water impacting the vent.
  • Steamhead
    Steamhead Member Posts: 17,010
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    Jughne's comment was meant to say that if your tap the elbow and put the vent there that any water pushed along in the steam main might wind up in the vent. If you put the vent on the downward leg after the elbow there is less likelihood of water impacting the vent.

    We tap the sides of elbows and tees all the time and never have a problem. Remember, the expansion ratio of water to steam is 1700:1, which means there is only a trickle of water in the bottom of the main.
    All Steamed Up, Inc.
    Towson, MD, USA
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  • rjp8292
    rjp8292 Member Posts: 10
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    > @Fizz said:
    > Are you having any issues with your system now?

    Yes. The system is poorly balanced. It was coal fired in its beginning. The master bedroom almost gets no heat unless you crank the thermostat up. It's the last radiator distance wise. The middle bedroom is mild at best and is second from last distance wise. There are no main vents.
  • rjp8292
    rjp8292 Member Posts: 10
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    > @Steamhead said:
    > (Quote)
    > We tap the sides of elbows and tees all the time and never have a problem. Remember, the expansion ratio of water to steam is 1700:1, which means there is only a trickle of water in the bottom of the main.

    I was actually going to cut the pipe below the elbow and re pipe it. Installing a 2" elbow with a 3/4 threaded outlet on top. I have enough clearance to make a menorah or antler to attach the vents to away from the elbow. I would just have to use a union to reconnect to the dry return. I'm thinking 2 #2 gortons as the main run is 41 feet.
  • ethicalpaul
    ethicalpaul Member Posts: 5,798
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    That sounds great to me. I can't imagine it needs 2" heading down like that but see what others think.

    NJ Steam Homeowner.
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  • JUGHNE
    JUGHNE Member Posts: 11,110
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    So you want to replace that 90 with a 2" X 3/4" X 2" heel inlet tee?
    That will put your venting in the danger zone for water "slugs".

    If installed there usually a short riser and then horizontal run to your antler for vent protection is installed.....minding head room for the vents.....the more vertical riser the better. Especially if you go with the B&J Big Mouths which have no float in them to stop water passing.

    Having unscrewed 100 year old steam welded 2" piping and hoping to only replace what I needed without cracking additional fittings I would go for the easier route.

    Being old and actually accused of working smarter, not harder, (sometimes called lazy), I would drill two 1/4" ports in the side of the existing drop pipes and mount a G2 on each with 90's and nipples to keep them upright. 6" risers on each to 1/4" X 1/2" reducing coupling.

  • rjp8292
    rjp8292 Member Posts: 10
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    Thank you
  • Coolmen
    Coolmen Member Posts: 22
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    would you drill into the side or the top of the pipe to tap into a 1/4"tap? or does it not matter as long as you have 6+ inches tall of the dry return