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Splitting steam pipe into two bathrooms

branimal Member Posts: 210
I have a steam pipe on the top floor of a 3 family building. I’m renovating the space and I have a steam pipe that rises into one of the the two bathrooms. It has some type of blowoff valve at the top of it.

I’d like to tee the steam pipe into 2 smaller heat pipes and send each pipe into a corner of their respective bathrooms.

I have access to the 2nd floor and 3rd (Top) floor. I’ve read that I can cut the couplings with an angle grinder on the 2nd & 3rd floor and break them off with a hammer / chisel. At that point I can install new pipes and tee them off as described above.

The couplings on each pipe are 24” off the finished bathroom floor.

I’ll turn the heat off over the holidays when my 1st floor tenant (only tenant) isn’t here.

Is this a good plan? How would you guys go about it?



    JUGHNE Member Posts: 11,021
    Your "blow off valves" are air vents, without them the pipe will not heat. The air has to be removed from the pipe thru them and then steam will close them. Each riser will need one. I would provide at least a 3/4" opening on the top. You can reduce down as needed for new vents.

    Your drawing introduces a "bull head" tee. Usually not what you want in steam.
    If you rotate/turn the tee 90 degrees and then use a 90 elbow off the top for one feed and the side branch of the tee for the other feed.
    Also any horizontal pipe must slope to drain water back down to the basement, this may require swing 90 elbow fittings.
    Any standing water will produce water hammer and your tenants will call, usually at 2 AM.

    BTY, that has some serious floor joist notching.
  • coelcanth
    coelcanth Member Posts: 89
    my 1920's house was built with risers like that in the bathrooms as well.
    they are fed by one inch pipe that enlarges to 2" immediately after passing through the bathroom floor. at nine feet long, the 2" risers go nearly to the ceiling. they get capped at the top with a normal pipe cap. about 6" from the top, the sidewall is tapped directly for a standard 1/8" radiator vent. i put the slowest vents on them, since they are basically the smallest radiators in the house. i used a rule of thumb of .5ft of steam per lineal foot of 2" pipe to estimate radiation.

    i'm not sure you would want to stop the pipe short as in your drawing. based on my experience here, i'd probably take a 2" riser the full height of the room..

  • branimal
    branimal Member Posts: 210
    Hi, thanks for the advice. I have a couple more questions.

    Is the following slope ratio correct:
    Laterals to radiators- 1/2 inch in 10 feet

    What type of pipe and fittings do steam systems use? Black pipe/fittings?

    Can I reduce the pipe size while it is under the floorboards? And emerge with 2" risers? If so what size can I reduce to?

  • branimal
    branimal Member Posts: 210
    Can I reuse the steam riser I already have? Or will the threads be shot?