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Baseboard radiator banging on one pipe steam

mjgordon Member Posts: 15

This is the only baseboard radiator in my entire house and it always bangs on start up but eventually stops during a cycle.

Questions for you:
a) what's the easiest first step in trying to correct this?
b) what radiator vent would you replace the existing one with so I can unscrew it in the future without having to dismount the whole radiator from the wall?

Several observations, some of which you can see in the pictures
1) Looks like kitchen was renovated about 20 years ago and this radiator replaced a traditional cast iron radiator as I can see an old hole in the basement looking up at the subfloor of the kitchen. From main to radiator is counterflow.
2) The radiator is almost completely flat, no back pitch. 1 1/4" pipe with fins
3) Total run out from the main is about 16 feet all in 1 1/4" black pipe. Back pitch for the first 3.5 feet is pretty good around 3.5"/10'. But it makes a 90 degree turn and the next 12 feet is about 1"/10' back pitch, which seems poor pitch and diameter for counterflow and that long of a run. Additional complexity is that this 12 feet runs through a series of rafters using many couplings almost no tolerance to gain more pitch. See my sketch
4) Vent. I can't tell what make/model since it is too tall and does not have clearance against the wall to unscrew it in place.
5) This radiator sits right above the area in the basement with a 275 gallon oil tank so making this parallel flow with a wet return would be difficult since getting the wet return behind the tank would be quite tough.


  • Jamie Hall
    Jamie Hall Member Posts: 23,323
    Long baseboards are problematic on one pipe steam, even when they have decent pitch --no matter what vent you put on them.

    Is there enough space between the joists and that oil tank in the basement that you could put a dry return in there? With good pitch? And run it off to somewhere it could drop to be wet? The return wouldn't have to be that big a pipe -- it's only carrying air and condensate, if you do it right, and so could even be 3/4 inch copper (Oh Heresy!). Then pitch the fin tube as much as possible in that direction, to be parallel flow? You'd still need a vent, but it could either be where it is now or relocated on that return.

    If there isn't enough height to do that, you might be able to accomplish the same thing with the return line above the floor under that fin tube, but I'd not be really happy with that as it looks as though you don't really have enough height to get any pitch on either the tube or the return.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 9,662
    You could try putting some shims of increasing thickness under the carriers to give the element some pitch and see if that helps before you go for the 2 pipe solution.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
    Varyvents fit the best but are too fast and would add to the problem . Two pipe as mentioned will be the best solution and add the vent in the basement. Another solution is replacing the baseboard with a radiator .

    There was an error rendering this rich post.

  • dopey27177
    dopey27177 Member Posts: 887
    Try this:

    At the back end of the fin tube install a 1 1/4" X 3/4" elbow. Install 3/4" copper tube and tie into the dry return. Connection to the dry return should be made this way.

    Go below the dry return about 12", Make a P trap, tie into the return from the bottom creating a water seal. The water seal prevents any steam in the dry return from entering the fin tube convector.

    Steam and condensate will flow to the return side and not be held in the convector.

    Pressure in the return is equalized by the pressure in the dry return and the water seal will not be blown out of the P Trap.


    Run the tubing into a wet return if one is nearby.