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Need advice on how to troubleshoot water hammering issue

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Philip_B
Philip_B Member Posts: 10
in Radiant Heating

Hi all,

So I have vertical supply pipe that runs from my basement to a second story radiator that is hammering every time the heating cycle starts going. The pipe is insulated in fiber glass in the basement, runs through my heated living room, and then into the heated bedroom above. The radiator itself has a recently new (purchased roughly a two months ago) Hoffman vent, and is pitched properly back towards the supply pipe. I'd say roughly 1/2 to 3/4 of a bubble on the level. At the end of the cycle I can sometimes here water dripping down into the supply pipe, with an audible thud.

The supply pipe in the basement obviously goes right to an elbow, and I'd say it has about less than 5' of horizontal pipe before it goes to the main supply pipe coming up from the boiler. So I'm not sure there is a lot of wiggle room to gain a lot of fall in the pipe in the basement.

Is there anything else I can do? This isn't like ting ting ting water hammer, this is like sledgehammer hitting concrete. I have listened in the basement and it is definitely isolated to this one pipe.

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 27,060

    How does the supply pipe run in the second floor? Straight shot down to the basement, or is there a horizontal section in there?

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Philip_B
    Philip_B Member Posts: 10

    @Jamie Hall - it's a straight shot. Radiator connects directly to the valve, and the valves on top of the vertical supply pipe. Supply pipe goes straight to to the elbow in the basement which is just above my stone foundation.

  • Grallert
    Grallert Member Posts: 1,083

    Is the horizontal pipe pitched correctly? Can you isolate the hammer? In the cellar? In the main?

    Miss Hall's School service mechanic, greenhouse manager, teacher, dog walker and designated driver

    ethicalpaul
  • Philip_B
    Philip_B Member Posts: 10

    @Grallert - as far as I can tell it is pitched down toward the main. There isn't a lot of run there so I'm seeing if I can lift the vertical supply any further and then put the radiator itself up on a wood platform.

    The elbow section didn't have any insulation, so I put 1" fiber glass (the proper heat rated version) around the whole thing, and I've ordered the regular white insulation sleeve to put there long-term.

    IMG_4616.jpeg IMG_4617.jpeg

    I think the hammer is right at the elbow. Because it is very audible on the 1st floor.

  • ethicalpaul
    ethicalpaul Member Posts: 8,462

    that’s where the water is collecting, cooling, then collapsing the steam that hits it at the next call for heat, then gets slung against the pipe.

    I had that and had to repipe it

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
    See my sight glass boiler videos: https://bit.ly/3sZW1el

  • Philip_B
    Philip_B Member Posts: 10

    @ethicalpaul - I think some repipping and potentially a boiler replacement is in my future, because the unit definitely wasn't taken care of properly before I got the house. There is also quite a bit of copper between the boiler and the mains, so it looks like it got jerry-rigged too.

    That being said, I've put new Hoffman 40 vents on all of the rads, replaced the auto water-feeder, and will replace the vents on the mains when its more conducive for me cutting them out (they're stuck beyond convincing, so I'm waiting for it to be less cold).

    ethicalpaul
  • Philip_B
    Philip_B Member Posts: 10

    So today I uncoupled the rad on the second floor, repositioned it a little bit, and exchanged the newish Hoffman 40 for one of the old Hoffman 1A's that was still reasonably in working shape when I changed them out in September. I set it to 6. So far no hammering. Will update everyone about if the "fix" continues to work or not. Not really sure why swapping out the vents and going backwards would make a difference, but I did it just because I had tried everything else.

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