pex sizing

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by mikeyvon, Jan 22, 2008.

  1. mikeyvon

    mikeyvon New Member

    Nov 14, 2007
    I am planning my supply runs and I have heard differing accounts on what size pex to run.

    I have 1" copper coming into the house from a 1" meter. I am unsure of what kind of pressure to expect. The meter is around 500' away with about 150' elevation rise to the house.

    I was planning on running a Trunk/branch type plan. with 2 main 1" trunk lines. Here are the fixtures and pex sizes I plan on running.

    Bath 1/Kitchen (they have a shared wall) - 1" trunk line T'd off main branch:

    Vanity - 1/2"
    Toilet - 1/2"
    Tub/shower combo - 3/4"
    Kitchen Sink - 1/2"
    Ice Maker - 1/2"
    Dishwasher (supplied off the kitchen sink line?)
    Hot/Cold outside house bib - 3/4"

    Master Bath - 1" trunk line (main branch):

    vanity x 2 - 1/2"
    toilet - 1/2"
    Steam generator - 1/2"
    Shower - 3/4"
    Soaker Bath - 3/4"
    Hand held for bath - 3/4"

    Other fixtures running off main branch -

    hosebibs x 2 - 3/4"
    Utility Sink - 1/2"
    Washer - 1/2"

    Does this setup sound ok? I have heard 3/4" trunk lines should be ok, but I also have folks telling me that I should use 1" to be on the safe side.

    Should I run the hot side as 1" also or 3/4"? I was assuming I would use 1" also out of the water heater.


  2. mikeyvon

    mikeyvon New Member

    Nov 14, 2007
    ps. I am not against I recirculating system for the hot water side, if it is simple to do.
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  4. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    I can see 3/4" for a large soaking tub.

    Unless you have mutiple heads, and body sprays on the shower, 1/2" would be plenty.

    Two lavs can be run on 1/2"
    If fact, with PEX, sometimes 3/8" is plenty for some fixtures.

    How long is the home from the water heater to the farthest fixture?
    What brand of PEX are you running?
  5. mikeyvon

    mikeyvon New Member

    Nov 14, 2007
    I will be running aquapex (wirsbo) with the propex tools.

    The longest hot water run is about 40' to the kitchen sink.

    So could I use 3/4" lines as my main trunk lines? or should I use 1"? With 3/4" trunk lines, I was concerned about pressure drop when using multiple fixtures.

    My carpenter used 1/2" pex lines on his house and says it is not enough, but it is also a function of pressure correct? He says he has low pressure. I am concerned about the pressure at my house do to the distance and elevation gain from the meter.
  6. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Aug 23, 2005
    I&C Engineer (mostly WWTP)
    Columbus, OH
    If you measure the pressure at your meter, then you can subtract your elevation change and your frctional losses in the pipe.

    150 ft elevation change (150 ft w.c) is 65psi.

    If you're water is moving around 2ft/sec through that pipe, you're looking at 5 psi for the pipe. So you'll need to overcome 70psi from loss alone.

    My pressure at home is around 65, so I hope that at your meter it is quite high!

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