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help - hammer in radiator



  • JH_2
    JH_2 Member Posts: 57
    edited December 2009
    Think I found the cause!! ...

    Ok I think I found the cause.  Lately as the heat runs more often, when there is a long time between cycles we are now getting a loud bang in the pipes right under our bed at the cycle start... right around the time the rads just start to heat.  You wil hear it tick.. tick. tick. BANG.   And then its all quiet until the net cycle.  Also the bedroom radiator vent is hissing and panting.

    Now down to the basement.  The takeoff for the bedroom radiator and the upstairs rad that originally caused the issue are in the same corner. All this time I was looking at the takeoffs but didn't pay much attention to the main, since the long section of main leading into this corner has a nice visible slope.  Aha - but here it is. After the corner, the last section of main before the drop into the dry return is sloped the wrong way!! So that corner where the takeoffs are is a low point in the main run - that's got to be the cause. 

    I sent some time loking at the pipe hangers and measuring the slope on the entire main, return to see If I can fix it with the hangars. I dont think that will work as the dry return is completely level also. If I try to lift taht low spot its only going to throw off the pitch of the long run so Im afraid I might have to get the plumber in to cut pipe and drop the end of the dry return an inch or so so we can fix the pitch.

    Luckily I have headroom to do it - I measured 31"  A dimension from the waterline to the end of that return.


  • Hammer

    Congratulations! It sounds like you have found the cause. The condensate collects in the corner until it is high enough to flow out. Between cycles the pooled condensate cools and when the new hot steam hits the cool condensate, the steam collapses causing the initial "bang" after that the condensate warms up enough to not collapse the steam. I imagine if you didn't have such good insulation the banging would be far worse.  Correct the pitch and that should fix it.

    - Rod
  • JH_2
    JH_2 Member Posts: 57
    edited December 2009
    lets see how this works.

    Ok... So I decided to give it a try anyway, maybe avoid paying the plumber if possible. I was trying to judge by measuring off the floor with a tape but I dont think the floor is exactly level either so...

    ... I put a couple of 3 foot levels both sides of that low spot and used a lally column to jack it up under the hanger.  Had to raise almost an inch just to get the last section level. At that point the long section dint have much slope so I set it at 1 inch and re-nailed the hangar.  Also raised the other end of the long section 1/4 in.

    We'll see if that makes a difference.  Have the wood stove heating the house today so probably no news for a couple days.

    fingers crossed...

    (EDIT - Just noticed that the water level in the boiler was 1/2" higher after I made these adjustments. I drained off.. must be over a half gallon of excess.. that had to have been trapped in that low spot! )
  • Jamie Hall
    Jamie Hall Member Posts: 22,050

    Dang... those sagged pipes will get you every time, eh?  I had the same sort of situation -- and the same sort of fix.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JH_2
    JH_2 Member Posts: 57
    So far so good!

    The stove burned down overnight and the heat kicked on around 5:45 just as I was getting up for work. No bangs from the main  this time, just the usual small ticks here and there of expanding pipes and shifting pipe hangars.  And the radiator vent didnt hiss much at all either.

    If it stays quiet for a couple days I will try opening up that upstairs radiator again.
  • JH_2
    JH_2 Member Posts: 57
    Mains still Quiet... But unfortunately the radiator continues to bang

    So a couple days later and still no hammer in the mains (Yeah!).  So being brave I opened the valve on the upstairs radiator again.

    No luck. Hammering in the radiator itself came back just as bad as ever. So its off again.

    Must be a bad radiator/metal expansion noise after all (ugh).

    I really appreciate all he help but sadly this mystery goes on.

    On the bright side I think this thread has set a record for page view in the steam forum ;-)
  • BenB
    BenB Member Posts: 1
    this post

    We're all waiting, have you fixed the slope of that pipe and has it fixed your banging?
  • JStar
    JStar Member Posts: 2,752

    Does the riser in the bedroom go directly to the upstairs radiator? Is there a chance that it makes a few turns in the floor?

    Are you fairly sure that the riser is only feeding that one radiator?

    Do you hear any unusual water noises in the riser at all? Gurgling, splashing?

    Did you check inside the riser pipe when you had the valve apart? It's possible that whoever changed the valve may have accidentally dropped a small tool or item down the pipe.

    I would also take a better look at the run-out in the basement. 1 1/4" is good for up to 55 sq.ft. but after a certain distance, if you can't get proper pitch, you should increase it by one size. Seems unlikely since you clearly hear the noise from the radiator. Just something to think about.
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