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Pipes banging no matter what I do

I removed a small radiator from a walk in closet last summer, and the source pipe is capped off.  About 6 weeks ago, I noticed a loud banging in my pipes when the heat (gas fired boiler, steam heat) goes on.  I purchased Dan's book, followed all instructions, but the banging still exists, although not quite as loud as before.  All of my radiators have been pitched to allow drain. (one pipe system)  My question is: does anyone think the problem is due to the removal of that radiator?  Is it possible that the "system" (irregular pressure distribution?)  is out of balance since taking that unit offline?  (I replaced all of the valves on the radiators)  I don't know what else to do, and before I call in an HVAC, I'd like be have an idea of what should be done.  No, I can't live with this noise, so please don't suggest that. :- )  I am in this house four years, and the problem only just started since removing the radiator.  Is that the problem?


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,575
    mysterious new water-hammer

    the removal of one [presumably] small radiator should not cause water-hammer to suddenly begin.

    when were the valves/vents replaced? were these the main vents? if they were the radiator vents, did you replace with the same type? if the radiator vents are too aggressive, and the main vents are inoperative, or under-sized, then the imbalance thus created can allow water-hammer.

    if during the work, the boiler water became contaminated with a bit of thread-cutting oil, then the waterline might become unsteady enough for the hammer to start, or if the boiler became over full. perhaps that radiator was holding a section of the main steam-line piping up straight, and without it being now connected the line is sagging causing a pool of condensate to be trapped in the way of the steam. check that your pressure is as low as possible as well.--nbc
  • Thank you

    Thanks for the response.  I replaced nearly all of my radiator valves about two weeks ago. the ones I removed were older than dirt and quite corroded. Before reading your reply, I thought that radiator vents were "one size fits all", and that's what I bought and installed.   Now I know that is not so.  So, my next question is, how does one determine the appropriate size/type radiator vent/valve to install?  I plan to call in a heating specialist to do this, but I'd like  to know what is the proper protocol for my own education and to make sure I'm not getting a song and dance. An educated consumer........you know the rest!
  • Jamie Hall
    Jamie Hall Member Posts: 21,573

    it is remotely possible that removing that one radiator did change something to cause a water hammer problem.  Not likely, I'll grant you, but possible.  It isn't likely that it is in the old runout and riser (now capped), but I would check to make sure that the runout still pitches back to the main.  I would also make sure that the main hasn't sagged, making a low point, where the old radiator was holding up the old riser and runout.  I've seen it happen.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • jpf321
    jpf321 Member Posts: 1,568
    exactly what I was thinking....

    i have a rad or two here that's "holding" up the main .. with the removal of a rad you could certainly get a main sag. 
    1-pipe Homeowner - Queens, NYC

    NEW: SlantFin Intrepid TR-30 + Tankless + Riello 40-F5 @ 0.85gph | OLD: Fitzgibbons 402 boiler + Beckett "SR" Oil Gun @ 1.75gph

    installed: 0-20oz/si gauge | vaporstat | hour-meter | gortons on all rads | 1pc G#2 + 1pc G#1 on each of 2 mains

    Connected EDR load: 371 sf venting load: 2.95cfm vent capacity: 4.62cfm
    my NEW system pics | my OLD system pics
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