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Thread: Another hot water mystery

  1. #1

    Default Another hot water mystery

    Thanks very much for any help with this.

    I have a tankless HWH that has basically been working as advertised.

    Took a hot shower this morning but came home to discover that I can't get the water to warm beyond luke (that's a term, right?) at the shower although it's piping hot at the lav. Went upstairs to the attic and the HW feed to the shower is hot to the touch.

    The only thing that's happened recently is that I turned off the whole-house valve to replace a hose bib outside yesterday. And FWIW, it's all copper pipe soldered everywhere except for two sharkbite fittings. And the tub hardware is a single handle sweeping from 7 to 12.

    Again, many thanks in advance.

  2. #2


    Hello, the problem is with your shower valve. We don't know the brand but most likely, there is a balancing spool in it that got stuck to one side. What brand of faucet do you have.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    There's likely a pressure balance spool valve in the shower control. When you shut things off, it often dislodges some crud and that might have jammed the spool valve or the filter screen to the shower valve (not all have a filter screen in or to the valve). The spool valve would normally slide back, but it might be stuck. This would turn off the hot to prevent scalding. Sometimes a rap with a rubber mallet frees it up, or taking it out and possibly cleaning...worst case, replacement.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4


    I think you guys are absolutely right. I remember thinking this morning that I shut the valve a little too vigorously. I think I remember it sleeves into some serrations. Hopefully I haven't stripped it too much.

  5. #5


    Okay. I guess you guys knew this already, but the serrated temperature range setting ring appears to not have anything to do with it. The set is by Price-Pfister. There are 4 screws holding a metal plate holding down, I assume, a flange on the valve. Where do I go from here?

    Thanks much again.

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