What is a tempering valve?
A tempering valve is a mixing device installed on hot water systems that blends incoming hot water with cold supply water to deliver a preset safe temperature at the outlet.
A tempering valve reduces the risk of scalding by automatically mixing hot water from a storage tank or instantaneous system with incoming cold water. It maintains a steady, safe delivery temperature even as demand and source temperatures fluctuate. The valve opens and closes internal ports to balance the flow and regulate outlet temperature without requiring user adjustment at the tap.
Australian Standards (AS/NZS 3500.4) mandate tempering valves on all hot water systems serving domestic properties, including hot water systems connected to bathrooms or hand basins. The requirement exists because water stored at 60°C or hotter can cause severe burns in seconds. By delivering water at around 50°C, tempering valves protect vulnerable residents, especially children and elderly people, from accidental injury.
Tempering valves are typically installed at the outlet of the hot water cylinder or at the hot water plant itself, rather than at individual taps. A licensed plumber sizes and commissions the valve to match the property's system type and flow demand. The valve requires periodic testing and maintenance to ensure it continues operating at the correct temperature setpoint and responds reliably to changes in hot or cold supply pressure.