What is a tempering valve?

Terry Smith • December 17, 2025

What is a tempering valve?  www.americanplumbingla.com 

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What is a tempering valve? 
www.americanplumbingla.com 
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A tempering valve is a plumbing safety device that mixes hot water with cold water to deliver water at a controlled, safe temperature.

What it does

Reduces very hot water from a heater to a preset temperature

Prevents scalding at taps, showers, or fixtures

Keeps water temperature consistent even if pressure or supply changes

Where it’s commonly used

Domestic hot water systems (homes, apartments)

Bathrooms, showers, sinks

Solar and heat-pump water heaters (which often store water at higher temperatures)

Hospitals, schools, childcare centers (where safety standards are strict)

Why it’s important

Water heaters are often set to 60°C (140°F) or higher to prevent bacteria like Legionella

Tempering valves typically reduce outlet temperature to around 45–50°C (113–122°F), which is much safer for skin

How it works (simple)

Hot water enters the valve

Cold water enters the valve

The valve blends them to a set temperature

Mixed water exits to fixtures

Tempering valve vs thermostatic mixing valve (TMV)

Tempering valve: Usually serves an entire house or group of fixtures

TMV: More precise, often used at individual outlets (like a single shower)
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