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Banging - steam boiler 1-pipe system

ksd99 Member Posts: 77
First, I really appreciated all the help that you all have given me in the last 2 years with my boiler – it has made a difference. I need some support regarding an issue with some banging. I have a riser that is in exterior wall that goes to the second floor, which connects to 2 rads – one in a bathroom and one in a bedroom. The issue is there is banging in the floor when the steam 1st comes up the riser; I think the pipe is hitting the floor but not sure. I put in adjustable vents and slowed the steam down thinking that might help – it did not make a huge difference. I then closed the vent to the bedroom rad – still noise. I then switched the process and closed the vent of the bathroom – perfect no banging just silence. Thinking the pipe from the riser to the bathroom rad might be sagging, I pitched the rad at the valve side thinking some tension might help – it did not. Any thoughts? I cannot get to the piping without taking up the flooring or going thru the ceiling on the 1st floor.
New owner of 1 Pipe Steam Boiler - learning all I can- no real steam pro in S.W. Michigan - if you know of 1 -let me know.


  • ethicalpaul
    ethicalpaul Member Posts: 5,731
    edited March 2020
    I think your search for a sagging pipe is the right one. The banging is likely caused by water lying in the pipe causing the steam to collapse to vacuum when the steam hits it. It only happens at the start of the call for heat because the water eventually heats up and stops collapsing the steam.

    I ended up abandoning my riser in my exterior wall and running a new pipe next to the interior surface of that wall (as I later found out it was originally built!)

    You might have to open a hole in the ceiling to find out for sure
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    Sometimes, raising all 4 legs of the rad, while still maintainIng the proper slope, will improve the pitch of the lateral horizontal pipe, so as to make it drain properly.
    You could do 4 quarters under the valve end, and 6 under the vent end, for instance.—NBC
  • BobC
    BobC Member Posts: 5,479
    I had to raise a radiator on the second floor a few years back. I put a 3/4" strip of plywood under the vent end and a 1/2" strip under the steam input end.

    Houses settle as the get older, i used a 2x4 and a fulcrum to lift the radiator. This allows you to do it gently and it will also tell you how far up you can go.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Grallert
    Grallert Member Posts: 657
    I used to carry a pile of washers about the size of quarters for adjusting radiators.
    Miss Hall's School service mechanic, greenhouse manager,teacher and dog walker
  • ethicalpaul
    ethicalpaul Member Posts: 5,731
    These can work if you're lucky. I raised mine 2 inches and it made things better (reduced banging), but there was still water lying in the runout.
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el