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Steam riser pipe type

Recently We were called to investigate a Single Pipe steam system for several Radiators that jus recently started to make noise, not quite banging, but never the less, noisy. We installed a new Atmospheric cast Iron sectional in the building about 2 years ago, and replaced several areas of wet return buried piping. After we were done, for about a year and a half the system ran without a sound. In Mid December another contractor came in a replaced a defective 1 1/2 Steel Riser. My concern is, they put in a copper pipe instead of steel, and it looks to be 1 1/4 as opposed to 1 1/2. Any thoughts, and if anyone has any code knowledge forThe Washington D.C area, that would help. Pressure on the boiler is at about 1 psi.


  • Fred
    Fred Member Posts: 8,542
    Black iron is the better option for steam mains and risers. Anything below the boiler water line can be copper. Most pressing concern with copper on steam mains/risers is that, over time, with the expansion and contraction, joints will eventually leak. Some can go for years, others relatively short term.
    Most likely cause for the noise is either 1) the contractor installed the copper riser up to a horizontal pipe and, in the process, pulled the horizontal down enough to cause it to lose its pitch and now it holds water and hammers a bit when steam hits that water or 2) the riser now rubs against a floorboard as it expands and contracts. Check where it comes through the floor and if it is rubbing, try inserting a strip of plastic milk carton between the pipe and the floorboard so that the pipe can slide.
  • JStar
    JStar Member Posts: 2,752
    edited December 2019
    The copper will cause long term corrosion to the system. It has to be taken out.

    The undersized piping is likely the main cause of noise, especially if it's gurgling or surging sounds. What's the EDR of the connected radiators?