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Thread: Is a Thermostatic valve on a new water heater setup important?

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    DIY Junior Member wombat's Avatar
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    Default Is a Thermostatic valve on a new water heater setup important?

    Is putting a thermostatic valve on a new water heater the preferred method now?
    Is this part of the 2009 Uniform code?
    Are these valves adjustable if you feel the water is too cold?
    What about if you want hotter water for your washing machine?
    (I saw one diagram where they split the washing machine/dish washer water off from the water delivered to the outlets)
    I have also seen mention that is wise to keep the hot water at 140 degrees and use the thermostatic valve to lower the temperature for deliver to prevent buildup of legionaires bateria.

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    Forum Admin, Expert Plumber Terry's Avatar
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    If you have a big tub in the home, they like to see a tempering valve.
    And yes, you can adjust the outgoing temperature, it's a mix from the cold and the hot.
    This way you can run the heater with a high setting, and then dial down the output.


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    Retired Defense Industry Engineer jadnashua's Avatar
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    You can also tap off before the tempering valve to places that can utilize hotter water safely, such as the dishwasher and washing machine (if you still use hot there).

    Bradford White has a neat packaged add-on tempering valve that you just screw on. They also have a digital temperature control that easily lets you change the temperature output. As part of that package, you can also add a leak detection/water shutoff device.

    Where I live, a tempering valve is required to get a permit and inspection of a new or replacement WH.
    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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    DIY Senior Member Runs with bison's Avatar
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    Our local UDO doesn't include these, tempering valves (fairly new update that my wife was instrumental in implenting). UDO was an advance but not cutting edge because that is what we could get in a conservative contractor environment--conservatives really hate change.

    An adjustable tempering valve would be nice...if if holds up for 10 years or more (do they? That's a question not a jab.) I'm not at all impressed by PRV's with respect to sustained performance and see them as a once every 2 years rebuild/replacement...meaning I need to do it myself so that I don't spend a fortune on plumbing contractors every two years for the most simplistic work. Wish I had required the PRV be installed in a manner that I could swap/rebuild by hand easily...won't make the same mistake again. My experience with PRV's suggests skipping tempering valves until absolutely required.

    Ideally I would only run the water heater high when I wanted to fill the whirlpool. The other 95-98% of the time running it hot would just be wasting money and energy. Of course the ideal is an "on demand" temp increase to do the job. I can already do this just by starting the fill, halting, then finishing after the water heater catches up. Granted, I would prefer to type in a profile somewhere and have it respond accordingly.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    The 'guts' of a tempering valve is essentially a bi-metalic spring - same sort of thing that was in the old, mechanical thermostats for your furnace. They can last a very long time. As the spring gets weaker, you can tweak it a little until at some point it needs to be either replaced or rebuilt. The one I have has an allen key hole in it to enable you to turn it. I just leave the wrench in it, but have not actually ever had to adjust it. There are some with a calibrated knob, but they cost more and I'm not sure they actually work better or longer. I'd think if you used it a lot, you might cause the seals to start to leak...they are more of a set and forget type of thing.

    One thing I like about the BW bits is it's easy to set a time limit on raising the temp. The worst thing to happen would be if it was raised, and then someone else needed to run hot and scalded themselves. The nice thing about a tempering valve is that if you need more hot water, you can raise the tank thermostat and still not have to worry about scalding anyone...it just mixes more cold to maintain the same temp.
    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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