Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Mixing Valve to get more hot water use

If I add a thermostatic mixing valve to the water tank and set tank temp. to 140 and valve to 125 will I get longer shower time?   Does the shower nit already have mixing valve at the tap as per code?   So would adding the MV to my tank still be beneficial?


  • Jamie Hall
    Jamie Hall Member Posts: 22,887
    Yes, in general, because what you will be doing is diluting that 140 plus degree water down to about 110, and then that will be what you are showering with. Yes, that is, if you usually shower with less than 110 water. Now if you really like your shower at 110 (and some do!) then no, you wouldn't.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 21,804
    Here is the math for equivalent tank volume. Assuming a 50 gallon tank water temperature of 50f. Use your actual numbers😉

    Note plumbing codes state water delivery not to exceed 120f in residential applications.

    So with 140 set point, 120 delivery you get 78.5 gallons
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    JUGHNE Member Posts: 11,021
    Most modern code compliant single lever shower valves are simply "Pressure balanced".
    That is if you are in the shower and a WC is flushed, dropping the cold water pressure, then the shower will in turn drop the hot water pressure. This pressure drop of both H & C is usually not noticed while showering. But without this feature you very well notice the loss of cold as your temp rises dramatically.
    In older institutions one would hear a flush valve activated and learn to step back from the water flow for a few seconds.

    As Tommay stated there may be a mechanical stop that is adjustable in the shower valve to limit the travel of the lever towards hot.

    That is OK to a certain extent of the shower, however the rest of the house can see the 140 degree at every other fixture.