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Steam pipe replacement

We are planning to replace a couple sections of ancient and leaking steel pipe on our steam system. The pieces are 2" sections, in the basement heading up via 1 1/2" pieces into the radiators above. After the run (the last 2 radiators on the line) the pipe steps down and drops to 1" returning back to the boiler.

We have done various plumbing repairs, but haven't done much with the steam system other than tighten and repack some valves and temp fix a hole or two with repair clamps. But we've surveyed the work area and feel we can handle removing the spent pieces and replacing new ones and using couplers to join the top and bottom pipes. Since we're in the middle of winter, our main concern is getting stuck. If we back ourselves into a corner after we've cut out the bad pipe, can we cap the line (and the one or two radiators above) without creating any issues with the whole system?


  • nicholas bonham-carter
    One-pipe or two pipe system?

    Is the replacement necessary because of a leak? Just make sure you keep the slope right, and even for the new pipes.

    If you have to cap off the supplies, and returns as a temporary expedient, the boiler will be temporarily oversized, and will short-cycle, so make sure you complete the repair as soon as you can.--NBC
  • Navigator
    Navigator Member Posts: 2
    Probably one pipe

    Thanks, and yes, leaking into the basement. Any capping would be done as a temporary fix to keep heating the rest of the building in case we need to call in help to finish the job. And, we're hoping it is a last resort option that we don't have to use!

    Oh and all the radiators connect to the system with one pipe so it's almost certainly a one pipe system.
  • Jamie Hall
    Jamie Hall Member Posts: 23,454
    If you find you have a steam line

    which is leaking, examine it rather carefully and find out what caused the leak.  If it is corrosion from outside, well and good.  Check the rest of the pipe to make sure that there aren't other weak areas.  On the other hand, if the corrosion is coming through from inside (which is rather rare, by the way), the chances of it being the only spot are somewhere between slim and none, and you would be well advised to replace the entire length which has the leak in it, rather than putting in a patch.  The cost or labour is in the work, not in the material, and it only makes sense to do it once.

    If there aren't handy unions, make sure that you use at least one to make things a lot easier to screw together!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England