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Pipes clanging/banging - need help- 4 questions

We have a one-pipe steam steam system with one boiler servicing 12 units (10 with steam, 2 basement units with hot water return). There is a radiator on the first floor that sounds like someone is inside the metal with a hammer and at time it is frightening and sounds like it is going to break. The sound resonates to the basement units and always happens when the heat goes on. We asked that the boiler be skimmed regularly. They drained water out the other night since it appears to over-fill (someone installed an auto feeder to a boiler that cannot use one so we have to hit the reset button continually when it shuts off). It still makes these cranking, wrenching sounds at all times of day and in the middle of the night. My questions are:
1) Will regular skimming of boiler fix this alone? If so, how often? We have a Weil-McLain Series 5 Gas-Fired Boiler.
2) The radiator valve and/or vent is not opening and closing properly on the banging radiator. The radiator is very old. One plumber lifted it out of the floor to install a new valve that didn't close initially. Now the plumber says it is a vent that is not working and to replace it requires more work (not sure what as he no longer services the building). Does this make any sense?
3) The thermostat is manual and not locked (not my idea) and when people get cold, they bump it up one notch - sometimes two. The noise follows. Should the thermostat be in the hands of any condo owner to change at will?
4) We had a pipe in the basement break recently and spread black sludge all over the residents' floor. It was hot and and dirty and very scary. Fortunately, no one was hurt by this. However, the sludge build up from the boiler to this basement unit could happen again. Does not skimming the boiler regularly cause more sludge and jeapordize the integrity of the heating pipes?
Any recommendations would be appreciated.


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Draining and refilling is not skimming-do a search for that here.
    Post some pictures of the boiler, and its piping for more advice.
    I suggest installing a Honeywell VisionPro thermostat with remote sensor on an interior wall in the most exposed apartment, so that the temperature setting remains constant.
    You probably need better main, (not radiator) vents as well, so that steam reaches all radiators at the same time.—NBC
  • Jamie Hall
    Jamie Hall Member Posts: 23,287
    What @nicholas bonham-carter said.


    The clanging and banging are almost always -- not always, but often enough to not matter -- to water being trapped in the pipes of the radiator. You say this is one pipe steam, so first, the radiator inlet valve must be a steam type, and must always be open. Otherwise it will trap condensate and bang. Second, the radiator must pitch towards the inlet valve -- not much; perhaps half a bubble on the level is enough -- but some. Third, all the pipes leading to the radiator must pitch back towards the main -- and I'd bet that's where the problem is. If you can, try lifting the whole radiator up about half an inch for starters and see if that helps.

    Also, go down below it and look at all the pipes leading to it and check that they do slope back to the main -- the required slope is 1 inch for every 10 feet of pie at a minimum.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JohnNY
    JohnNY Member Posts: 3,230
    Where is this building located?
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
  • dopey27177
    dopey27177 Member Posts: 887
    Check and see if the the hot water loop is isolated from the condensate return piping.

    To isolate to condensate return from the water heating system you may need to install a swing check valve with a soft seat.

    I have seen several installations of this type and they were equipt with a master steam trap and condensate feed water pump set.

    There is a possibility that the circ pump is to powerful and forcing some water into the condensate return.