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Source of Water Hammer (pic included)

Until the water laying in that badly pitched pipe heats up , I bet it sounds like sledge hammers hitting railroad spikes . Why someone would install it that way is anyone's guess . I've seen some piping that'll make your hair turn white . Is this new work ?


  • Mark Gibson
    Mark Gibson Member Posts: 21

    Hi All,

    I have an oil-fired single-pipe steam system from ca. 1924. Parallel flow/up-feed, dry return. Generally it works well, but I've had water hammer (mostly on startup) in the piping to one of my rads since I bought the house.

    I started by checking that the rad itself was tilted toward the valve to let condensate out. It is. Then I looked at the pipe to it. Pretty standard -- a 10' or so run of insulated pipe, pitched correctly, hangers in place, not appearing to sag. At the main is where things got confusing.

    See the picture. The pipe at the top of the picture (the one with the probably-not-OK-for-steam foam insulation) is heading over your left shoulder to the radiator. You can see on this end that it drops down via a few elbows and nipples, then pitches _UP_ (I checked this with a level), and then drops into the main. At this point, I'm thinking that would create a perfect spot for condensate to hang out and create water hammer.

    Note also that even though every other rad is fed from a main that loops around the basement (and condensate flows in the same direction as the steam), for this one rad only (which happens to be the first one served), the condensate has to counterflow back into the boiler.

    Am I missing something? Is there a good reason why you'd do it this way? I should mention that this pipe actually crosses over the other end of the main loop -- so the installer used extra pipe and fittings to hook it up this way.

    Thanks for any and all help, and happy holidays!
  • Mark Gibson
    Mark Gibson Member Posts: 21
    Funny you should mention that...

    Thanks Ron...

    On startup it is just as you describe. Loud, single bangs, spaced 1-2 sec apart. But after a while it settles down into more of a quiet rattle that appears to come from the hand valve on the radiator. In fact, I can exacerbate that second rattle by partially closing the hand valve (needless to say I don't leave it that way). Different problem?

    New work...maybe if by "new" you mean after 1924. :-) The rad in question is in the kitchen which I believe has always been there, and the offending pipes and fittings look the same age as the others. I see similar wrench marks on them. That said, the boiler was replaced in the last 15 years or so, so the near-boiler piping had to have been touched at least once.

    So should I just take advantage of that conveniently-located union and re-pitch the pipe (maybe replace that vertical nipple with a close nipple?) Or should I have a plumber run it into the main like the others? In other words, if the present pipes were pitched correctly, would this be an acceptable setup? Or is it just inherently bad?
  • Norm Harvey
    Norm Harvey Member Posts: 684

    That equalizer looks pretty improper also
    "We see the world as WE are, not as IT is, because it is the "I" behind the EYE that does the seeing"
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