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Moving radiators in a converted gravity system

plumb1pa Member Posts: 9
I've got a customer who wants to move 2nd floor hot water radiators from one room to another. They are fed by a one inch supply and return line (two radiators off one supply and return) can I just cut them out and reroute the piping with 3/4 heatpex? Or do I need to keep the one inch. I'm concerned about flow.
It's an old gravity system that someone else converted I can't see how it works the way the boiler is piped, but he says the heat has been fine. Thanks in advance.


  • Jamie Hall
    Jamie Hall Member Posts: 23,524
    If you are concerned about maintaining balance and have no other way to do it, stick with the 1 inch. The difference to 3/4 inch doesn't seem like much, but the latter will have twice the velocity -- and 4 times the head loss.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • plumb1pa
    plumb1pa Member Posts: 9
    Ok, thanks
  • kcopp
    kcopp Member Posts: 4,444
    Be careful... Keep the runs the same length as before. Gravity systems can be tricky. Dont trap piping... keep the same pitch as before.
  • pedmec
    pedmec Member Posts: 994
    agree with jamie. If your adding piping and fittings to move it your also adding head loss to it so reducing size will make it that much worse.