thermostatic shower valve question

Discussion in 'Shower & Bathtub Forum & Blog' started by MP5SDA3, Dec 30, 2007.

  1. MP5SDA3

    MP5SDA3 New Member

    Dec 26, 2007
    So I got my brand new thermostatic valve, diverter and test valve set up going. When I turn on the volume control lever I get good flow from the hot side for a few seconds, then it slows to a drip. When I override the anti scald feature it does not seem to help at all. Am I doing something wrong here? The water temp on my tankless heater is set to 112 degrees so I am thinking that it should be good to go. Also cold flow just fine.

    Thanks in advance for any feedback.
  2. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    I hope some guys with great tankless experience can help us here. My suspicion is that a thermostatic valve may "fight" with the temp control on the tankless. You could also call the tankless manufacturer and see what they recommend.

    I seem to recall that there can be issues with pressure balanced valves with tankless, and the thermostatic may also be a problem.
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  4. MP5SDA3

    MP5SDA3 New Member

    Dec 26, 2007

    Funny you should say that because I wondered about that. The tankless HW heater has been both a blessing and a curse to me. All the things they don't tell you about it's limitations for example. I had a big fight with it and the pressure balancing shower and faucet valves which are single handle types when I installed it several months ago. The problem is IMHO, that the WH is just too smart sometimes...

    Thanks for the feedback!

    Happy New Year!

  5. GrumpyPlumber

    GrumpyPlumber Licensed Grump

    Jun 18, 2007
    Plumber, self employed
    Licensed Grump
    The only possible relation to the tankless would be that they now come with flow restriction devices that slow down the flow when it can't keep the water hot enough at the set temperature (112 in your case).
    This really shouldn't be a problem unless it's slowing it down due to overheating above 112 (haven't heard this being an issue before, but don't know what model tankless you have).
    I might try turning up the temp on the tankless and modifying the anti-scald at the shower, 112 is max temp for a shower, but you really want 120-130 for the Kitchen and lav.
    Ten to one, this is a problem with the valve...relative question is how well do other fixtures flow on the hot..while the shower is both running and not?
    Last edited: Dec 31, 2007
  6. MP5SDA3

    MP5SDA3 New Member

    Dec 26, 2007
    Good points thanks!

    The HW is a Bosch 2400 LP model. It has been in service for 6 months. Flow and temp to other taps is great, but have not tested with the rough in and another tap yet, (will do so now). Temp setting at the heater is 114, since the shower valve is the only mod I have made to date, I am suspisious about it first. I have tried adjusting the temp control on the valve unit but that does not help. More to follow, thanks for your feedback!

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