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Thread: 3/4" vs. 1/2" supply to shower?

  1. #1
    DIY Junior Member
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    Default 3/4" vs. 1/2" supply to shower?

    Doing a remodel. Existing 1/2" supply lines to shower. I can replumb with 3/4" supply, but shower head is to a standard 1/2" stubout. Is there any advantage to converting to 3/4" supply line from main, or is the 1/2" a limiting factor? I'm installing ZOE industries Polaris II double shower head.

  2. #2
    DIY Senior Member SteveW's Avatar
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  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default pipe

    IF your shower valve will only flow as much, or less, than a 1/2" pipe can supply, which is very likely, then there is no advantage to using 3/4" supply lines.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Default

    A 3/4" valve can flow as much as twice as much water as a 1/2" version of similar design. But, whether you need it or not depends on how much water the heads need to provide decent spray. And, unless you have 3/4" supply lines, a 3/4" valve will only give you marginally better flow if fed with a 1/2" line, if at all.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Default valve

    A 3/4' ceramic seat valve has openings LESS than half the size of a 3/4" pipe. First you take away the space needed for the rim of the seal, then divide the remainder into four pie shaped pieces. Two of them are open for water to flow and two are closed for shutoff purposes. Then take away the space needed for the webs between the quadrants and you are left with an area about the same, and maybe less, than a 1/2" copper line. Take a stem out sometime and measure the area of the two openings.

  6. #6
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Default 1/2" vs 3/4"

    I would switch the lines to 3/4" for sure unless you are piping in 1/2" copper.

    Compare the inside measurement of a pex fitting 1/2" vs 1/2" copper and you will see a big difference.

    If you are re doing your bathroom do it right and re pipe it with a new home run. Insulate the pipes and strap them down.

    Good Luck.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

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