Grohe 34126 thermostatic valve problem

Discussion in 'Shower & Bathtub Forum & Blog' started by jalmora, Mar 7, 2013.

  1. jalmora

    jalmora New Member

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    Mar 7, 2013
    Location:
    Anchorage, Alaska
    Hey there. I purchased a Grohe 34126 thermostatic valve in 2006. Installed in 2009. Been just fantastic all this time, but recently I am unable to get really hot water, the kind that makes you want to stay in the shower. I can get hot hot elsewhere in the house, but not the shower or tub. It hits a certain moderate temperature and will not increase. A lot of the info I find out there is for new installs, but mine was working just fine and only recently has been a problem. Any ideas? Thanks.

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    Last edited by a moderator: Mar 7, 2013
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Retired Systems engineer for defense industry.
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    New England
    YOu may need to check the inlet filter screen or check valve for crud...it may have a restriction, preventing it from getting more hot into the valve. IF that doesn't fix it, it may need a new cartridge.
     
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  4. jalmora

    jalmora New Member

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    Total nonplumber here. What do you mean by the cartridge? I won't be doing this myself, but am trying to gather information for the nice guy who will. Thanks for responding, btw.
     
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
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    Occupation:
    Retired Systems engineer for defense industry.
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    New England
    The moving parts inside are typically called a cartridge and are replaced as a unit. Many of the Grohe valves have a little set of checkvalves in them - those have a small moving part, and a filter screen. If that gets jammed up, it will disrupt the flow. Same thing with the inlet filter screens (most of the Grohe valves use them). If you're on a well, you may have some occasional sand that gets in the system...that could clog some things up eventually. It could come through the town's water system, but isn't as common.
     
  6. jalmora

    jalmora New Member

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    Thank you Jim.
     
  7. jalmora

    jalmora New Member

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    Mar 7, 2013
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    Anchorage, Alaska
    If this double posts, sorry. We received from Grohe and installed a new cartridge. We cleaned the filter screens. Now we get scalding hot water for the first approx 5 seconds before it adjusts to that same "just below comfortable" moderate setting. We can get very cold water on demand, but not that good shower temperature. Any ideas?
     
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Did you follow the calibration procedure on the new cartridge?
     
  9. jal

    jal New Member

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    Aug 11, 2012
    Location:
    New York
    Same problem here - Scalding hot water - basically cold water is not mixing - I thought thermostatic valves are supposed to shut down if only hot water is flowing - it is a brand new valve - so not sure what to look for ... Calibration attempts dont do anything only hot water. How do you troubleshoot the valve and determine is not good?
     
  10. Smooky

    Smooky Well-Known Member

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    Apr 4, 2011
    Location:
    North Carolina
    Do you know if the hot is connected to the hot side of the valve? Could the hot pipe be connected to the cold side of the valve?
     
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