Watts USG-B Thermostatic Anti-Scald Valve (Under-the-Sink Type)

This valve is installed on the water pipes under the sink and mixes cold water into the hot water pipe to a safe pre-set maximum temperature before it flows out of the faucet. Referred to as “point of use” tempering valves or thermostatic mixing valves.

You’ll need to tell the plumber the maximum hot water temperature you’d like at the tap. Consider 110º F, the maximum temperature allowed in nursing homes.

We hired a plumber who hadn’t installed this type of valve before. It took him 2 hours, including a trip to the local hardware store to pick up additional materials. Our copper piping was one-half inch but the valve required one-quarter inch, so the plumber had to buy 2 extra valves and 2 extra tubes. We, of course, were not expecting this. But we now have water flowing out of the hot faucet at a safe temperature. We set it for a maximum 110 degrees; previously it was a whopping 150 degrees! Our installation charge was in hundreds of dollars.


  • In your own home, you can set the hot water heater at the higher temperature (140º F) necessary to reduce risk of bacterial growth in the hot water tank.
  • It’s especially helpful for apartment dwellers who do not have access to the hot water heater.
  • You determine the maximum hot water temperature before it flows out of the faucet.
  • You can reset the water temperate if needed.
  • The valve has a safety cap to protect against unwanted meddling.


  • Installation.The instructions say to “remove” piping, so we were surprised when the existing pipes had to be cut. The instructions should have said that you needed “to cut and replace existing pipes.” The instructions do not give any warnings to check the size of your existing pipes to see if they match the size of the valve openings (as our did not).

TIP It would be easy to misplace the small hex wrench needed to lock/unlock the valve handle to change the water temperature, so be sure to store in a safe place!