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old radiator conversion to hot water

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Hot water rads have an air bleed valve at the top. The bleeder for one-pipe steam rads is about 2/3 of the way down. They're tapped the same.

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  • doug o'connor
    doug o'connor Member Posts: 17
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    how easy is it to convert old radiators to new hot water heat systems.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
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    I presume you mean rads used on steam systems?

    If so, not too terrible provided the sections are connected across the top as well as the bottom. If no top connections there is no practical way to use them with hot water systems and there is no practical way to bleed the air.

    If from a one-pipe steam system, removing the old plugs can be a royal pain, but certainly doable. Old tapping bushings usually remove (if necessary) with comparable ease. 36" or even larger pipe wrench is best, but you can sometimes get by with a good-quality (not Chinese import) 24" wrench and long breaking bar. I once snapped a cheap Chinese pipe wrench using a breaking bar--for a moment I thought it my arm that had broken!

    Steam rads tend to collect a lot of gunk so make sure you flush them very well.
  • Tom Kane
    Tom Kane Member Posts: 56
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    rads

    I've got a similar question, but the reverse. What is required to convert cast iron radiators, previously using hot water, to a one-pipe steam system operation. I understand that they require one end to be plugged, pressure tested then an air vent added, but is there something fundemental that I might be missing?

    thanks, mark
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
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    You're not missing anything at all. Any cast iron rad suitable for water will work for steam but there are "steam only" cast iron rads. By the 1920s or so I'm pretty sure that "steam only" rads had gone the way of the dinosaurs.
  • Eric Johnson
    Eric Johnson Member Posts: 174
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    vent hole

    Does he need to cut and tap a hole about halfway up the side for the vent, Mike? All the steam rads I've seen have it there.

    I've got one of those old one-pipe steam rads running in a water system, but I had to turn it upside down to fill it, then isolate it and vent the rest of the line up to the isolation valves. Not something you'd want to get into the habit of doing, but it really kicks out the heat.
  • Phil_6
    Phil_6 Member Posts: 210
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    you can do it

    If you drill and tap a 1/8 hole for a coin air vent near the top of each section. I have one in my powder room I did like that. I put the vents on the back of the sections a little below the top and had them powder coated along with the radiator. Works fine and you can't even see them.
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928
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    Yes, plug the steam vent and drill/tap the top air bleed vent. Pretty sure both are 3/8"; 32 threads per inch. You can use a short bolt to plug the unused holes.
  • Eric Johnson
    Eric Johnson Member Posts: 174
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  • Tom Kane
    Tom Kane Member Posts: 56
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    Mike T., with regards from going to hot water to steam, you mention top air bleed that needs to be added. I do have one, and only one that has not only a mid level air vent/valve but a top air bleed as well. As for the others I am converting from water to steam, I would just add the mid level air vent similar to the other. Am I correct? And thanks for you help.

    mark
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