By mixing hot water with cold water, the tempering valve enables hot water to be kept at a temperature that kills bacteria while distributing it to the fixtures at a temperature that won't burn people. By adjusting the tempering valve's adjuster, the required temperature may be set for the valve. A thermostatic mixing valve can hold water at 1°C +/- and responds more quickly to changes in incoming water temperature than a tempering valve, which is accurate to around 3°C +/-.
