New mixer in second shower causing temperature control issues in first shower.

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Sam Jameson, Apr 15, 2019.

  1. Sam Jameson

    Sam Jameson New Member

    Joined:
    Apr 15, 2019
    Location:
    Indianapolis
    We converted a tub to a walk-in shower last year. Installed a new mixer, and replumbed the shower head. Everything went according to plan and we've had no issues. Fast forward to this year - we're renovating the second bathroom and installed a new mixer (just extended existing plumbing to a new area, no other changes). Now we're having serious temperature issues in the original shower. If the shower is running and you flush the toilet, you get scalded. If someone runs the sink in the kitchen for even 5 seconds, you lose all your hot water, and the bathroom sink won't get warm at all if the shower is running. What could be causing this??
     
  2. plumber69

    plumber69 In the Trades

    Joined:
    Jun 20, 2014
    Location:
    Prince Rupert, British Columbia
    If I understand right sounds like you may not have the new ones cartridge in and would cause a cross connection
     
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  4. hj

    hj Moderator & Master Plumber Staff Member

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    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    IF you have not finished the new shower, the "plumber" did not install either the cartridge OR the "anti crossover" plug in the valve.
     
  5. Sam Jameson

    Sam Jameson New Member

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    Apr 15, 2019
    Location:
    Indianapolis
    Thank you both! This should sort itself out once we can rebuild the walls and install the trim then, right?
     
  6. hj

    hj Moderator & Master Plumber Staff Member

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    It should "sort itself out", when the installer inserts the 'anti crossover plug' that came with the valve.
     
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    FWIW, not all valves these days come with the anti-crossover plug...it's an optional extra. But, the simple fix if you don't have that would be to install the cartridge in the new valve body unless you do have the plug available. WIthout the trim on, it may take a bit to ensure it is in the off position prior to turning the water back on, or you may take an inadvertent bath!
     
  8. hj

    hj Moderator & Master Plumber Staff Member

    Joined:
    Aug 31, 2004
    Occupation:
    Plumber
    Location:
    Cave Creek, Arizona
    They may not if you buy the complete fixture, but then the cartridge is supposed to be installed.
     
  9. plumber69

    plumber69 In the Trades

    Joined:
    Jun 20, 2014
    Location:
    Prince Rupert, British Columbia
    This problem gets asked at least once a month on here
     
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