Adjustable Mixing Valve

I saw my first adjustable mixing valve on a hot water tank at a 30 day warranty inspection today. When I cranked it up the temperature measured at a nearby laundry tub was 54C. Not too impressed.

What is wrong with 130 degree water for domestic use.?:slight_smile:
It scalds in 17 seconds . Mine is set for 108,°F







2 hours

3 hours



20 minutes

45 minutes



15 minutes

20 minutes



8 minutes

10 minutes



2 minutes

4.2 minutes



17 seconds

30 seconds



3 seconds

5 seconds

***Activation temperature = 120° max(response time is less than 5 seconds)**The above table shows that a person will receive a second degree burn in 3 seconds of exposure and a third degree burn in 5 seconds of exposure to water of 140°F at the discharge outlet will ensure the most safety for users.The American Journal of Public Health prefers a maximum temperature of 120°F for hot water.
The Consumer Product Safety Commission and the plumbing industry have published a voluntary standard which states that the maximum allowable temperature at the water outlet to the bathing area should be 120°F.
There are national standards set forth by the major plumbing code making bodies, which specify a maximum temperature of 120°F for delivered hot water. The major code making bodies include:

  • Southern Building Code Congress International (South)
  • National Association of Plumbing, Heating and Cooling Contractors (NJ, DE, MO, NE)
  • Council of American Building Officials (Regulate 1 & 2 family homes in U.S.)
  • International Association of Plumbing and Mechanical Officials (West)
  • Building Officials and Code Administrators (Northwest and Midwest)

Other nationally recognized plumbing code bodies that have published or proposed standards specifying 120°F as the maximum allowable discharge temperature include:
American Society for Testing & Materials (ASTM F444-88) Standard Consumer Safety Specification for Scald-Prevention Devices and Systems in Bathing Areas.
American Society of Sanitary Engineers and Plumbing Manufacturers’ Institute (ASSE 1016) - Individual Thermostatic Pressure Balancing and Combination Control Valves for Bathing Facilities.
American Society of Sanitary Engineers and the Plumbing Manufacturers’ Institute (ASSE 1062) - Temperature Actuated Flow Reducers for Individual Fixture Fittings. Passed the ASSE Standards Committee - April 26, 1996
Other organizations that specify a maximum of 120°F for delivered water temperature include:

  • Burn Prevention Foundation
  • National Safe Kids Campaign
  • American Society of Plumbing Engineers
  • American Trauma Society
  • Shriners’ Burn Institute
  • National Burn Victim Foundation
  • American Correctional Association
  • U.S. Dept of Health & Human Services (guidelines for hospital & medical facility construction)

Code here is 49C max (I know…we don’t do code).

What does “cranked it up” mean in the context of a mixing valve? Did you crank it up to deliver the highest or lowest temp?

I don’t mess with them myself. If they deliver water at more than 120F to a two handled tub faucet, they are wrong

I turned it up to see what the highest temperature a home owner could adjust it to.

Got it. Then I’m not sure what the issue is. The mixing valve generally should be set to 120F / 49C as the max temp. Of course it can’t put out water at a higher temp than the water heater no matter how it you crank it up.

What was your concern?

Why would you do that . If the home had a pressure reducer would you turn that up to see what pressure they could get at the taps too .
This to me is just a big waste of time and could be asking for trouble if the valve was to fail when testing it.

I agree with Roy.

Why mess with it at all?

Do you also test TPRs?

I only tried it because I had never seen one before. Now that I know they can be overridden to exceed the maximum allowable I probably won’t bother again.
In new housing, which this was, the rules that call for smoke detectors, a CO detector, etc also require:

7.6.5. Water Temperature Control Maximum Temperature of Hot Water
(1) … the maximum temperature of hot water supplied by fittings to
fixtures in a residential occupancy shall not exceed 49°C.
(2) Sentence (1) does not apply to hot water supplied to installed dishwashers or clothes washers.

Thanks for the answer… John

Not the first time I see a tempering valve setting at 130 degrees.

Doesn’t mean you have to set it there for hot water at the faucet.

I could keep my 40 gal. storage tank off the furnace at 150 degrees if I wanted too.

Off course I don’t. :slight_smile: