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  1. #1
    Join Date
    Mar 2009
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    Virginia
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    Default Radiator knocks when I walk by

    The radiators in my 70 year old house knock (same sound as air in the pipes) when I walk by. This happens whether the radiators are hot or not anytime of year. The noise goes away for a while then knocks again when I walk by hours later. I did move the radiator pipes around in the basement a few years ago (b/c I moved the boiler) but I do not remember if it made that noise before then. Any thoughts?

  2. #2
    Join Date
    Mar 2009
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    1,387

    Default Re: Radiator knocks when I walk by

    Quick call gostbusters...Or might there be a pipe that clangs from the load on the flooring... Is this in all the rooms or one or adjoing room?

    Oh by the way i have several really heavy radiators that are too stinking heavy top knock you can have them, there in the middle of Nebraska ..... see my post on how to bust up to demo them .

  3. #3
    Join Date
    Feb 2008
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    556

    Default Re: Radiator knocks when I walk by

    ArlingtonJon:

    Are we talking about hot water rads or steam rads???

    Possible cause for steam rads of the single pipe variety would be lack of pitch of the rad supply pipe back to the boiler, trapping water (condensate) in the bottom of the rad---check for adequate pitch with a torpedo level.

    Possible cause with hot water rads would be lack of clearance for the supply/return risers (vertical pipes from rad thru floorboards.

    Please post back with more info.

  4. #4
    Join Date
    Mar 2009
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    Virginia
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    Default Re: Radiator knocks when I walk by

    NashuaTech, thanks for the reply. The radiators are hot water radiators that have a separate entrance pipe and exit pipe. What do you mean by "lack of clearance for the supply/return risers (vertical pipes from rad thru floorboards." Clearance from the hole in the floor around the pipes?

  5. #5
    Join Date
    Feb 2008
    Posts
    556

    Thumbs up Re: Radiator knocks when I walk by

    ArlingtonJon:

    Yes, the pipes rubbing as they go thru too-tight floorboard holes is the major cause of pipe banging in hot water systems---another major cause is not enough pipe clearance in runs of the supply pipes (usually in the cellar/boiler room)---both symptoms are caused by the considerable expansion of metal pipes when they heat up from room temp to 180 degrees--it's normal for a long run of metal pipe to expand over an inch.

    The first thing to do is exactly LOCATE THE SOURCE OF THE SOUND when the system is heating up--it often helps to hold a short length of plastic/rubber hose to your ear so you can exactly locate the source of the noise.

    If it's coming from a floorboards hole, get a tube of high-heat caulking compound (big box stores or plumbing supply) & caulk the offending access hole---this usually cures it, otherwise you'll have to widen the access hole.

    If the noise is coming from a run of pipe in the cellar, the pipe may have to be shortened or slightly redirected after the system is drained.

    Also check the metal pipe holders that support the pipes in the cellar---if they are too tight, try loosening the part that comes into contact wih the pipe to allow a little play in the support bracket as they expand when heated---there is also a high heat wheel-bearing grease (automotive) that can be applied to the pipe brackets.
    Last edited by NashuaTech; 03-29-2009 at 04:13 PM.

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