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Adding cast iron baseboard to one-pipe steam system

I just purchased a 2' section of Weil McClain CIBB with 3/4" taps to add to a small bathroom on the second floor that currently has no heat. I have a 1-1/4" steam pipe that ends under the bathroom floor where I'd like to add the baseboard.

How do I pipe between the 1-1/4" supply line and the baseboard? Do I bring the 1-1/4 up through the floor to the baseboard and than drop the size down to 3/4" or should I drop the size down before going up through the floor? And where do I add a valve; before or after the bushing?

Is it even possible to use this 2' baseboard on a one-pipe system? I read some comments about piping it 2-pipe and attaching it back to the supply line. That would be difficult for my situation since currently the 1-1/4" pipe is in a joist bay and the end of the radiator would be in a separate bay and I'd rather not drill through the joists for this. My assumption was that I could just pipe into one side of the baseboard and install it tilted back like a radiator. Then the condensate would flow back toward the pipe.

Thanks for your help.


  • IronmanIronman Member Posts: 5,641
    CIBB on One Pipe

    How is it gonna vent?
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • JohnNYJohnNY Member Posts: 2,443
    Not for 1-pipe

    Ci BB doesn't work well with 1-pipe steam.

    If it's your only option and you need heat in the room, then you wouldn't be wrong to try it.

    A 2" section won't produce much condensate and the reality is that you wouldn't be the first person to use the product with livable results.

    If you must use it, vent the radiator with a ¾" x ⅛" bushing, a ⅛" nipple and elbow, and convector (straight) air vent.
    For troubleshooting and private consulting services, find John "JohnNY" Cataneo here at :
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    Or email John at [email protected]
    John is the Boilers and Hydronic Heating Systems Course Instructor at NYC's Mechanics Institute, a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
    John also oversees mechanical installations and maintenance for metro-area clients with his family's company, Gateway Plumbing and Heating along with his brother/business partner.
  • JStarJStar Member Posts: 2,752

    I've always wondered what would happen if you piped it like a two-pipe BB but had the return tie back into the supply riser. Never tried it. Seems like, at the very least, you would create two supplies to handle the condensate that just one 3/4" supply might not tolerate.
  • STEAM DOCTORSTEAM DOCTOR Member Posts: 1,164

    Not sure if that would work. If steam approaches the rad from both sides,the pressure would equalize and steam probably wouldn't enter the radiator from either side. 1 1/4" baseboard is probably the best way to go if you absolutely need to have baseboard
  • kevin_58kevin_58 Member Posts: 61
    cast iron baseboard

    I ran into 1 tied in 2 pipe. It didnt work, The return line shut off the air vent before it got hot. It was on the 1st floor with an unfinished basement so i put a 30 inch deep trap on the return with a drain valve on the bottom. it worked a lot better but not perfect.
  • JStarJStar Member Posts: 2,752

    I guess it would only work if the air vent was in the dead center of the BB.
  • NJSteamhouseNJSteamhouse Member Posts: 29
    Pipe Size?

    So if I run the one-pipe up to the radiator, should I keep the pipe size at 1-1/4, including the valve and then use a 1-1/4" to 3/4" bushing at the radiator?
  • STEAM DOCTORSTEAM DOCTOR Member Posts: 1,164
    1 1/4"

    Best bet is to use 1 1/4" baseboard.
  • SteamheadSteamhead Member Posts: 13,825
    If that cast-iron baseboard is only two feet long

    it should work with just one pipe. We've gone up to three feet with no problems. 
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • NJSteamhouseNJSteamhouse Member Posts: 29
    3/4" Baseboard

    I already have a 3/4" baseboard in place. I just need to determine how to run the pipe to it.
  • JStarJStar Member Posts: 2,752

    I would use an 1-1/4" angled valve with a reducer on the spud. This will allow the water to drain freely from the BB and give you the benefit of a bigger sized valve to allow steam and condensate to live happily together.
  • NJSteamhouseNJSteamhouse Member Posts: 29
    Reducer on the spud?

    Which specific fittings should I use?

    Would I use the 1-1/4" angle valve with spud and then one of these?:

    If so, how do I then connect to the radiator? With a short 3/4" pipe? I'm not sure if there is a difference with the threads on a spud versus a regular fitting or pipe.
  • stox_12stox_12 Posts: 1
    Please post a picture of the valve side for a baseboard install.

    planning to do a similar install with a 2ft governale baseboard and just not sure the best way to install reducer due to concern of steam and condensate through the 3/4" opening. Thanks.
  • jumperjumper Member Posts: 1,453
    piping two pipe into one pipe

    Worked for me on fin tube terminals. So it should work for a small baseboard. How much heat I can't say. You only need a small pipe on low end for condensate and air.
  • Charlie from wmassCharlie from wmass Member Posts: 4,123
    CIBB will work fine

    you need to pipe it two pipe if it is over 4' long. the return end needs either a trap or a water seal and a vent on the return end of the baseboard. As for putting the vent in the middle, it is hard to guess where the steam thinks the middle is as it is never the measured middle of the unit and it would have steam crashing together coming from each end.
    Cost is what you spend , value is what you get.

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  • VA_BearVA_Bear Member Posts: 50
    edited March 2014
    Two pipe components on one pipe systems

    I suspect the CIBB baseboard's passages would be too small to operate effectively piped as a one pipe device and would heat up as the initial steam enters and the air vents at the far end, however as the condensate builds up and restricts the passage, enough steam could not enter to continue to heat and the steam would tend to push the condensate up into the baseboard as it attempts to flow past the condensate, eventually flooding the baseboard until the boiler shuts off and gravity can overcome the steam flow. I have a church with a one pipe system which has a couple hundred feet of similar 3/4" baseboard which behaves admirably tapped off of two inch headers which make the transition from one to two pipe. with the condensate return pipe running just below the baseboard back to the header.
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