Mom washing childs hands in warm tempered water

What is a Tempering Valve and Do I Need One?

Did you know that it’s an Australian regulation to have a tempering valve installed? Like most people, you might be wondering, what is a tempering valve? Here’s everything you could ever want to know about your tempering valve.

What is a Tempering Valve?

Tempering valves are a valve that restricts the temperature of hot water that can be used in your home. More specifically, fixtures that use hot water for personal hygiene purposes, for example, the shower.  It only takes half of a second for 70°C  hot water to give a child third-degree burns. Hot water system tempering valves only allow a maximum of 50°C hot water to be used.

Tempering valves have become a regulation in Australia to prevent scalding from hot water, especially in young children. The thermostat of your hot water system tank must be set to 60°C or above to prevent the growth of harmful bacteria such as Legionella bacteria. This requirement needed to be balanced with the risk of burns, and so a hot water tempering valve was made mandatory.

A tempering valve is only required for homes that have a storage tank for their hot water. Homes that use continuous flow hot water don’t need these valves as there is no stored hot water which is prone to Leigonella bacteria growth.

How Does a Hot Water Tempering Valve Work?

For something that can control hot water temperature, tempering valves are quite simple in how they work. They are a three-way mixing valve. One allows hot water in, a second pulls cold water in from the water supply, and the third is the exit for the 50°C water. In between letting the hot and cold water in, and letting out the tempered water, the temperature of the water is adjusted.

Inside the tempering valve is a thermostatic element. This is submerged in water and is sensitive to water temperature changes. In response to temperature changes, the thermostatic element expands and contracts. This motion controls a piston that opens and closes the three inlet and outlet valves. The piston action selectively mixes hot water with cold water to be mixed until 50°C is achieved. Then, and only then is the outlet valve opened to deliver hot water to the fixture.

The thermostatic element is accurate within 3°C. This means that the hot water coming out of your fixture will be plus or minus 3°C to whatever temperature it is set to.

Where is the Tempering Valve Located?

Most tempering valves are installed at the hot water system. Alongside the tempering valve, isolating valves, line strainers and check valves must also be installed at the cold and hot water inlets. Depending on the water pressure, pressure reducing valves might also be required.

Before installation even begins, the plumbing system must be flushed to prevent a buildup in the valve. This buildup will not only impact the performance of the tempering valve, but it will potentially void the warranty as well!

A hot water tempering valve must be installed by a licensed plumber.

Can You Adjust Tempering Valves?

Your tempering valve can be adjusted using a knob. Most can be set anywhere in the range of 35-55°C. Adjustments must be made by a licensed plumber and must be no higher than 50°C.

If you choose, however, your tempering valve can be set lower than the 50°C maximum! If you are installing a tempering valve with the intention of protecting the young or elderly, perhaps consider a thermostatic mixer. We’ll be touching on this hot water valve shortly.

What Happens When a Tempering Valve Fails?

Given that the tempering valve regulation was introduced to prevent scalding from too hot water, you might worry about it failing and hurting your family during daily personal hygiene purposes. As water temperature increases, the contact time required to receive a third-degree burn decreases:

  • 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 – approximately 5 minutes for adults and children

Thankfully, most tempering valves have a thermal shut-off feature that closes the cold and hot water inlet valves in event of a problem. If this isn’t the case with your tempering valve, you will at least be able to notice when your water is hotter than usual.

If your tempering valve does fail and you notice your water temperature is too high, you should contact a professional plumber to fix the problem. Until the problem is solved, be sure to monitor any children when they are using hot water.

How Long Do Tempering Valves Last?

Your tempering valve0 is like any other plumbing fixture – over time they will deteriorate. Provided you keep up with your plumbing maintenance, you can expect your tempering valve to last you 5-8 years.

We find most tempering valves need to be replaced due to a buildup. Your water contains minerals and other materials that can accumulate in your pipes and fixtures over time. This accumulation eventually impacts the performance of your fixture, and in severe cases will stop it working entirely.

This is why your plumbing system needs to be properly flushed by a plumber before they even begin installing a tempering valve. Regular flushing will also help to prolong the life of your tempering valve, a well as other plumbing fixtures!

Filters are often recommended to be installed to prevent the buildup from occurring in the first place. An older hot water system and its associated tempering valve are especially prone to rust and buildup and so should be checked more regularly.

Tempering Valve Vs. Thermostatic Mixer

Domestic homes require a tempering valve, however, businesses that care for children and the elderly, such as child care centres and nursing homes, use a different valve. This is the thermostatic mixing valve.

A thermostatic mixing valve works by the same mechanism as a tempering valve, but are faster to respond and are more accurate. Water temperature coming from a tempering valve is accurate within 3°C, while a thermostatic mixing valve is only out by 1°C! In addition, thermostatic mixing valves must be set no higher than 45°C.

This is important for those with more compromised or sensitive skin, such as those in nursing homes. 45°C is a much safer temperature to prevent damage and injury here.

Tempering valves are a critical component of your hot water system and how it is delivered across your home. Mixing your hot water with cold water from your water supply is a major component of protecting your family.

To learn more about the best hot water system for your home, you can read Hot Water Systems: The Complete Guide. Contact Metropolitan Plumbing for your local tempering valve experts.


Published: 17 Jul, 2020

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