Piping type for recirc lines

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by ckl111, May 8, 2009.

  1. ckl111

    ckl111 Home Builder

    Apr 23, 2009
    Home Builder
    Do recirc lines require the copper pipes to be thicker? Type M or Type L ?

    I was wondering if the constant movement of water would slowly corrode pipe faster.
  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    It will, but mainly because the return circulation pipe is usually smaller so its velocity it higher, unless you install a valve BETWEEN the pump and heater, NOT BEFORE the pump, and close it until you have just enough flow to keep the line warm.
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  4. franck@geneseo.net

    franck@geneseo.net New Member

    Apr 13, 2009
    How quickly might one expect errosion to penetrate the wall of copper tubing? In my proposed re-circulating system I'll be using Type L, 3/4" return line in a gravity flow system.
  5. FloridaOrange

    FloridaOrange Plumbing Designer

    Dec 2, 2005
    Plumbing Designer
    SW Florida
    You should be fine with the 3/4" type L.

    I was just reading an ASPE article yesterday on recircing systems. The author recommends not going smaller than 3/4" due to velocity and using balancing valves to control the flow as hj suggested.

    Curious, on plans I always call for Type L copper for the water lines (when specifying copper anyway), do you typical use Type K?
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