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Thread: multi zone supply & return spacing 8"... 4" ??

  1. #1

    Default multi zone supply & return spacing 8"... 4" ??

    I am building a multi-zone hydronic system and am wondering how far the supply and the return lines (3/4") should be spread apart where they meet the main loop. I am using a 1-1/4" main loop and there are 6 zones coming off of it eash with its own Grundfos UPS15-58 circ pump.

    I have heard that the reducing tees should be no less than 8" apart. Some other site suggested 4". Can someone elaborate as to why this distance is important. I assume it is so that there is no crossover pull from the cold water side.

    What is the proper separation distance for the tees.....? How far apart can I put the tees and maintain effectiveness.??


  2. #2
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default heat

    From the information you give, there is no way to answer. It depends on the type of distribution system and the type of tees. The basic answer, is that there must be as much resistance between the tees, (and neither 4" or 8" is enough in most cases unless they are diversion tees), as there is in the branch circuit, otherwise the water will flow directly past the branch without sending any water to the radiation.

  3. #3
    Master Plumber nhmaster's Avatar
    Join Date
    Jul 2008
    S. Maine


    The closer the better. remember that water always follows the path of least resistance. When you start getting over 8" then the path becomes a very short loop. You can not get them too close.


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