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Thread: Master Bath Plumbing kerfluffle

  1. #1
    DIY Junior Member Elizabeth Sauro's Avatar
    Join Date
    Oct 2011

    Default Master Bath Plumbing kerfluffle

    Hello! First I want to thank the members of this forum for providing such a great educational tool. Many of the concerns I am going to express in this post stem directly from the information gleaned in reading different topics. My contractor and I are currently at odds regarding the plumbing in the master bathroom. He think I've been spending too much time on the internet, and I think he is not taking into consideration how different the fixtures I'm using are from what he has installed before. I'm getting a toto Neorest 550, a high volume tub filler, and a shower with 2 showerheads and 4 or 6 body jets (I was planning the Kohler DTV system, but have not completely finalized that.) There will be two sinks.

    The issue is 1/2" pex and my understanding that it is not sufficient to supply these fixtures. I've stressed this from the beginning but 1/2" is what he's used before so 1/2" is what was bought. He is using a manabloc. He says that since 3/4" is coming into the house, larger pex will not have any pressure. It is my understanding that pex and copper have different interior diameter dimensions. The pressure coming into the house is 55 psi. Currently the walls are exposed, but not for long. I want to prevent a costly mistake, does anyone have any advice? I am open to anything at this point.

    One of his arguments is that the shutoff valve for the neorest is 1/4" so it doesnt make a difference if the pex is 1/2 or 3/4. But if that is the case, why are there reports of insufficient pressure with 1/2" pex?

    Thanks in advance for any consideration.

  2. #2
    DIY Junior Member Elizabeth Sauro's Avatar
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    Oct 2011


    anyone know how to make a username less descriptive? facebook is annoying! I feel stupid using my whole real name.

  3. #3
    DIY Senior Member kreemoweet's Avatar
    Join Date
    Sep 2009
    Seattle. WA


    You need to stop that "contractor" in his tracks, and make him do an actual flow test on the piping he has installed. Get the specs from the
    fixture literature and make sure the water supply system can deliver. 1/2" PEX to a tub filler is completely absurd. Do not allow this "contractor"
    to proceed until he corrects this error.

  4. #4
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona


    1/2" PEX SHOULD be adequate for flushing the toilet, but NOT for the tub/shower system, depending on the incoming pressure and how the REST of the piping is arranged. After he installs the PEX, make the recommended volume test to see if you get 1.5 gallons in 10 seconds.
    Licensed residential and commercial plumber

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    If I remember correctly, the Neorest installation manual warns that 1/2" pex will not provide proper flow. This toilet does not operate like a traditional one, and needs proper flow to the pump to operate, and 1/2" pex does not have it. As I understand it, it does not have a tank, and uses the pump to flush, thus, operation does depend on the supply...it comes with its own shutoff valve to ensure it has the proper sized outlet.

    And, 1/2" pex won't supply much more than 5-6 gpm, so would be totally inadequate for a multihead shower with body sprays, or to fill a large tub in a timely manner. SOme of the high performance fillers want 1" supply (which you don't have), and 3/4" copper at the minimum.

    If you haven't already addressed it, you'll need a significant water heating system as well.
    Last edited by jadnashua; 10-23-2011 at 03:09 PM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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