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How to Regulate the Hot Water Heater

Updated: Nov. 28, 2019

Install temperature regulating valves without tearing up the bathtub wall

How to Regulate the Hot Water HeaterFamily Handyman
Control the hot water temperature at faucets and showers that don't have anti-scald valves by installing either a mixing valve or a point-of-use tempering valve.

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Two methods of controlling hot water temperature

Photo 1: Water heating mixing valve

Cut the copper pipes at your water heater and reroute them through a mixing valve. Install a temperature gauge in a tee fitting near the valve to set the output temperature.

Photo 2: Tempering valve

Install a “point-of-use” tempering valve below the sink. Shut off the supply valves and disconnect the existing supply tubes. Add the tempering valve and two new supply tubes.


Turn on the hot water and adjust the tempering valve to obtain 104 degrees F. or less.

If your home is plumbed with copper pipe, you can install a mixing valve right at the water heater and set the maximum temperature to 104 degrees F. You may still get some temperature variations due to fast changes in water pressure (such as from a toilet or a washing machine), but there will be no chance of scalding.

But before you break into any pipes or buy a water heater mixing valve, ask your local building inspector if your code requires “point-of-use” tempering valves at each faucet. These valves may be cheaper than installing temperature-regulating faucets.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Adjustable wrench
  • Rags
  • Soldering torch
  • Tube cutter

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • Copper pipe
  • Flux
  • Mixing valve with thermometer
  • Point-of-use tempering valve
  • Sanding cloth
  • Solder