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water hammer with large radiator

toraziyaltoraziyal Member Posts: 12
We have a one pipe steam system. We have this large radiator on the second floor, 15 sections. We are experiencing very loud water hammer as it starts to heat up. It also doesn't get warm all the way across.

Unfortunately, the return line runs across the middle of the house under the floor boards so we can't see if that line is tilted properly. I haven't tried to raise the radiator yet, however, it is tilted properly back to the return.

We can't really tell if the water hammer is coming from the radiator itself or the return lines somewhere. It's so loud we actually just shutoff the intake to this radiator last winter. :).

It also has a shiny new adjustable vent the same as we've used on all the other radiators.

I could try a smaller radiator that I have kicking around. I don't think we really need this large radiator where it is since it's an open space and we've got two other smaller radiators in 2 rooms connected to this one. We could eventually move it. Thoughts on next steps? Try raising the radiator first? Try the smaller radiator?


  • BobCBobC Member Posts: 4,552
    What kind of vent. If it's a Hoffman or Ventrite you might want to vent that large radiator slowly so it produces less condensate. If it's one of the Chinese adjustables (Durst is on brand) it really isn't adjustable.

    You could try lifting the whole radiatot up 1/2 to 1 inch and see if that helps. Get a couple of 4 dt 2x4's and some short ones to use as a fulcrum and gentle lever it up and put something under the legs, recheck it with a level to be sure it's still sloped towards the input side.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • toraziyaltoraziyal Member Posts: 12
    They are Ventrite no 1s. I set it to between 1 and 2 to see what happens. I do however feel that if I vent it slowly, it doesn't even get hot before the desired temperature is hit.

    I'll see if I can't jury-rig something to lift it. I have some checkers I can put under the feet.
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,655
    Quarters work well as shims under the feet, and by varying the number, can allow for pitch.
    The problem with switching a radiator to a different location is the connection from the valve to the radiator, known as a spud, should be changed as well. The valve and spud are a mating pair, which may not seal if mismatched.—NBC
  • FredFred Member Posts: 5,712
    You mention you shut the "Supply" off and you also mention "the return pipe". Is this a one pipe or two pipe radiator? Is the supply and return that you mention the same pipe or is there a separate pipe on each side of the radiator? Does it appear the floor has sagged under that radiator? If so, it is most likely the supply pipe has lost its pitch and holding water. Try raising the entire radiator and then re-pitching it.
  • toraziyaltoraziyal Member Posts: 12
    It's a one-pipe system.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 2,852
    @toraziyal as @Fred mentioned you mentioned return pipe. There is no return pipe if this is a one pipe system. How about some pictures
  • mikeg2015mikeg2015 Member Posts: 151
    On ventrite 1. I think 1 is off. 2 oddly I think vented more than 3 or 4. Check the balancing chart this on this site.
  • toraziyaltoraziyal Member Posts: 12
    Soooo, we finally got a chance to raise the large radiator about 1/2 inch. We sent the vent-rite to 3. No more clanking and the radiator gets hot! Yay us.

    Now, we seem to have water hammer in another radiator, not as loud though. It's more like a thud, thud, thud, than metal on metal.

    We'll try to raise that one tonight, but is it common for water hammer to suddenly appear in another spot if you've made a change to another radiator?
  • FredFred Member Posts: 5,712
    It is certainly possible if the second radiator is attached to the same feed and supplies steam to both radiators.
  • GrallertGrallert Member Posts: 171
    It's possible that the pipe supplying the thudding radiator has been moved in the process of raising the of radiator. It's very likely that now you have a pipe that moves along a floor joist or such as it heats causing that thud thud thud sound.
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