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Mixing 1/2 PEX and 3/4 PEX in a single zone

dgkula
dgkula Member Posts: 59
Question for the pros please: I have a single zone in my basement which is plumbed off a manifold with 1/2 PEX to 15' of fin tube (based on 3/4 copper pipe). I want to add a second radiator to this zone to heat a soon to be finished area of the basement. A plumber has proposed adding 8' fin tube and running 3/4 PEX, splicing that into the return from the 1/2 PEX, creating a single loop consisting of source >1/2 PEX > 3/4 fin tube > 1/2 PEX > 3/4 PEX > 3/4 fin tube > 3/4 PEX > return. Is this going to be OK? Naively I would think that single diameter for the whole run would minimize changes in pressure throughout the zone for a constant flow rate but I don't know if it matters. Of course an option is to have him re-plumb the original 1/2 for 3/4 PEX so that all diameters are the same but I have read that PEX expands as it heats ...

Thanks!
David

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,170
    It's fine. Won't change the pressure much. The additional piping -- of any size -- and fin tube will increase the pressure drop around the loop, but not by much for that length.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Zman
  • Zman
    Zman Member Posts: 7,561
    Your 23' of baseboard will put out round 13,000 btu. You only need to move around 1.3 gpm. That should be easy with the piping you described.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein