What is the function of a tempering valve?

A tempering valve mixes hot and cold water to deliver hot tap water at a constant temperature. Tempering valves have a temperature sensitive element which adjusts the mix depending on the temperature of the incoming water flowing through the valve. The mechanism is a sliding valve that varies the ratio of hot and cold water that is allowed to pass. The valve is designed to maintain a constant outlet temperature, reducing the risk of accidental scalding.

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