Why a Tempering Valve is so Important to Your Hot Water System

When you step into a steaming hot shower, you may not realise the crucial role that your tempering valve plays.

The same can be said for using hot water in any other way – washing dishes, in cooking, cleaning your car or scrubbing your hands – the tempering valve keeps you and your family safe.

What is a tempering valve and why is it so important to your hot water system? Let’s examine what they are and why state regulations have made them mandatory in tank storage hot water systems around the country.

What is a Tempering Valve?

Hot water in a tank system is stored at a temperature of at least 60°C. The reason for that high temperature is to ensure that dangerous Legionnella bacteria, which causes Legionnaires’ disease, can’t grow in your hot water system.

However, it would take five seconds for an adult and only one second for a child to experience third-degree burns if water was delivered at that temperature. That’s why your hot water system has a tempering valve.

The tempering valve essentially stops scalding hot water from pouring out of your taps. That’s why tempering valves are mandatory with all storage tank systems. There’s no need for a tempering valve with continuous flow (or instantaneous) hot water systems because no hot water is stored.

Where is the Tempering Valve?

A tempering valve is located externally on hot water systems. It is usually installed between the cold-water line and hot-water line.

It is possible to adjust your tempering valve. This adjustment has to be done by a licensed plumber, though, and the maximum temperature must be no more than 50°C. However, you can have your tempering valve set lower than 50°C, and many systems are set at lower temperatures than the household maximum.

For example, some organisations such as schools, nursing homes and hospitals use a thermostatic mixing valve. This is similar to a tempering valve but operates more quickly to changes in temperature to deliver water at 45°C or lower. Thermostatic mixing valves are accurate to within 1°C.

What if a Tempering Valve Malfunctions?

If you notice that your hot water is pouring out of your taps or shower head at a higher temperature than before, don’t hesitate to call a plumber to get your tempering valve checked.

It is alarming to know just how quickly you or your family can receive third-degree burns from hot water that is not adequately controlled by a tempering valve.

  • 70°C – 1 second for an adult, 0.5 seconds for a child
  • 60°C – 5 seconds for an adult, 1 second for a child
  • 55°C – 30 seconds for an adult, 7 seconds for a child
  • Less than 50°C – about five minutes for adults and children.

Most tempering valves have a thermal shut-off safety feature that closes cold and hot water inlet valves if a problem occurs. However, not all of them have this feature. If you notice your hot water is getting hotter than normal, be sure to contact a qualified plumber to check your tempering valve.

Types of Tempering Valves

If your tempering valve is starting to fail and you’re in the market for a replacement, there are several types to choose from.

Factors such as the size and type of your hot water system can ultimately determine your choice of tempering valve. The different types include:

  • Black Cap Tempering Valve – recommended for large storage hot water systems.
  • Blue Cap Tempering Valve – ideal for electric hot water heaters.
  • Orange Cap Tempering Valve – a high-performance valve which is recommended for heat pump systems.
  • Green Cap Tempering Valve – suited to gas hot water systems.
  • Yellow Cap Tempering Valve – recommended for electric and gas hot water systems.

How Long Do Tempering Valves Last?

As long as your hot water system is well maintained, your tempering valve should last 5-8 years. The reason most tempering valves need replacing is due to a buildup of minerals and other materials in your system.

The accumulation of minerals and other impurities will eventually have an impact on your tempering valve and, in more severe cases, stop it working completely. That’s why your plumbing system should be completely flushed by a licensed plumber before they begin to install a new tempering valve.

In Summary

The tempering valve is so crucial to the safety of your hot water system it’s hard to believe most householders don’t know more about it.

However, just being aware of how crucial it is makes all the difference. As long as you recognise the signs that your tempering valve may be starting to malfunction, you’ll be able to contact a qualified plumber to inspect it and replace it, if necessary.

Please note: This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See our Terms & Conditions here.





Last Edited on: 30th November 2022