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Steam leak in in-wall convector (Herman Nelson Invisible Radiator)

Hi all,
I've noticed a tiny leak in an in-wall convector. It's fairly subtle, but it is audible during the steam cycle as a whine/gurgle sound, and the leak can be pinpointed by running my eyeglasses along the convector and noticing when they fog up.
This is a Herman Nelson Invisible Radiator from circa 1929 (period photo attached, thanks to Frank "Steamhead" Wilsey for the pdf this came from!). It is part of a residential 2-pipe system running at minimal pressure, new Weil-McLain boiler. The convector heats adequately as far as I can tell.
My questions are : 1) is this type of small leak potentially reparable, or will I need to replace the convector; 2) What is a good source for a replacement if I go that route?


  • nicatniter
    nicatniter Member Posts: 38
    Well I've pinpointed the leak to an area on top of the convector reservoir, where the leak shows up only as a slight moistening on the surface during the time the convector fills with steam. It seems like it ought to be repairable without ripping out the wall and everything, but maybe I'm overly optimistic. For example if I cleaned up the area and was able to get a solder probe down to the surface, maybe it could be plugged that way. I dunno - anybody have experience with this sort of repair?
  • Fred
    Fred Member Posts: 8,542
    edited December 2014
    If you can clean the surface really well, you might try an epoxy repair. Just make sure it is for high temp surfaces. A plumbing supply house may recommend one or Jb-weld has one that should work.
  • KC_Jones
    KC_Jones Member Posts: 5,737
    Devcon is another brand that makes a really good epoxy. If you are going to try that route the most important part is get the metal really really clean. Typically epoxy fails in these applications (as many things do) due to bad surface preparation. you want the epoxy on metal not rust or paint or anything but "virgin" metal.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • nicatniter
    nicatniter Member Posts: 38
    Thanks for the advice, it looks like I'll be shopping around for a good heat-tolerant epoxy resin. Cleaning shouldn't be a problem, as I can just slip a pan underneath and have at it with a slim brush. (While I'm at it, I might as well clean 85 years of dust and grime off the whole thing!).

    I'm amazed at how well these devices heat our first floor rooms! Their traps (Webster 512) are up close to the ceiling in the basement, and I'm about ready to do some replacing, as I suspect most haven't been touched in a long time.

    Happy New Year to all the steamheads, here's a picture of one of our Invisible Radiators keeping the living room warm on a 1 F winter night.