Monoflow vs. Strait loop

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Peter57, Nov 27, 2011.

  1. Peter57

    Peter57 New Member

    Messages:
    3
    Location:
    Connecticut
    Hi all:
    I'm replacing a 60 year old copper/monoflow system with PEX, and am considering a strait through loop. I could use some advice.

    The heating is for the first floor, 1 zone, about 750 sq. ft. I plan to branch off from a common 1 inch PEX feed into two 3/4 inch loops of approx. same size. The baseboard is Hi output slantfin (80) with 3/4 inch copper. Strait thru is so much simpler than monoflow, but are their disadvantages with strait thru? Why was monoflow even used in the first place? Am I doing the right thing??

    Also, do I need bleeders in a strait thru loop? (I will put shutoff valves in each zone)

    Regards, Peter
    Last edited: Nov 27, 2011
  2. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,793
    Location:
    Long Island, NY
    With monoflow Tees, you can shut off each baseboard radiator without shutting off the flow for the entire loop. If you have no need to be able to shut off individual radiators in the loop, I don't know if you'd need those tees. I never worked with PEX, but I've read that the effective sizes are different than those of copper because of the wall thickness, so you'd need to go up a size to get the same flow rating.
  3. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,225
    Location:
    Maine
    Go with loop piping, there is way less pump head loss. I would bring each loop back to the boiler manifold rather than split 1" pex.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,815
    Location:
    Cave Creek, Arizona
    quote; Go with loop piping, there is way less pump head loss

    I doubt that that is true because a Mono-Flo system uses a larger main "loop" which creates LESS flow restriction.
  5. Peter57

    Peter57 New Member

    Messages:
    3
    Location:
    Connecticut
    Thanx. I don't really need to shut off each baseboard. I've resched the PEX wall thickness and you're right, it is a bit smaller.
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