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Total Newbie pipe size question- adapting pipe sizes

glxie63 Member Posts: 1
Such a newbie I don't even know which category to put this in so...Main Wall! I've ordered new steel radiators for some renovation in my house. Contractor told me 3/4" pipe. New rads are 1/2" pipe. (Other radiators are simply old school cast iron in other parts of house.) Is this simply solved with pipe adaptors? Please say yes. (That's what rad company said but would like to hear from unbiased knowledgeable folks.) Thanks for any feedback


  • Jamie Hall
    Jamie Hall Member Posts: 15,415
    Yes. There are adaptors and fittings available to adapt pretty much any pipe size -- or material -- to pretty much anything else. That said, your local big box store will probably look cross-eyed at you for even the simplest things -- but they are out there, and easy to get. And usually cheap. It's a matter of knowing what you need to adapt to what, and going from there.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ironman
    Ironman Member Posts: 6,333
    Adapting the pipe sizes is simple as Jamie pointed out, but adapting new low mass steel panel rads to a system with old high mass cast iron rads is not so simple. Even if you size them correctly, the new rads will not perform like the old ones. Also, the old piping system needs to be considered carefully. Is it an old gravity direct return? A monoflo?

    At the very least, the new rads should be put on a separate zone with their own circulator and thermostat.

    If you post some pics of your boiler, piping and old rads, that would be helpful in giving advice on how to proceed.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • WMno57
    WMno57 Member Posts: 187
    1/2" NPT, or 1/2" BSPP (British Standard Pipe Parallel thread), or 1/2" BSPT (British Standard Pipe Taper thread?

    Tell us more about the new radiators.
  • hot_rod
    hot_rod Member Posts: 14,561
    Yes, many imported radiators would have a BSP straight thread, be sure to check.

    With some tweaking you can put a male BSP thread into a female NPT, Loctite or hemp :) But not a male NPT into a female BSP, only 1 or 2 threads will engage.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
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