What is a Tempering Valve and do I Need One?

Hot water from the tap is one of the greatest luxuries of modern civilization, and one we take for granted every day. But did you know there’s a whole set of dedicated plumbing regulations designed to keep your hot water safe? Not just in terms of cleanliness, but also to ensure hot water doesn’t put your family at risk of life-threatening burns. A simple, three-way device known as a tempering valve ensures a safe temperature in both your hot water tank and taps.

What is a tempering valve?

A tempering valve is a device fitted to a hot water storage system to regulate temperature. It’s only necessary for hot water storage systems – that is, a tank of water stored in or outside the home, typically heated by electricity or gas. Tempering valves aren’t usually required for continuous “on-demand” hot water systems, where the water is heated as you use it, as these systems are built with temperature controls.

How does a tempering valve work?

While all hot water storage systems must be kept at a minimum temperature of 60 degrees Celsius, the water flowing from your taps must not be above 50 degrees, so a tempering valve works by mixing hot and cold water together to produce a safe water temperature.

The three-way valve is connected to both your hot and cold-water systems. When you turn on the hot water tap, hot water is instantly pulled from the tank. The valve then adds cold water to the hot, using a submerged thermostatic device to ensure it reaches 50 degrees or less. Once the safe temperature is reached, the valve opens up and allows the water to flow to your tap.

Why not just make the hot water tank less hot?

It might seem like the easiest solution, but doing so introduces another major health risk: the growth of legionella bacteria.

Legionella loves to grow in warm water, with a special fondness for pipes and other plumbing apparatuses. Inhalation through a poorly maintained air conditioning unit, or an old bathroom tap, can lead to a rare but severe illness called Legionnaires’ Disease. If not caught in time, Legionnaires can be a deadly form of pneumonia.

Therefore, to prevent the growth of legionella, it is a legal requirement in Australia for all hot water to be stored above 60 degrees.

While Legionnaires’ Disease is much more likely to happen in a large-scale commercial or industrial setting, there is still a risk of it occurring in the home. For this reason, a licensed plumber installing or working on your hot water tank will ensure the temperature remains at this level.

Why is 10 degrees such an important difference for hot water?

Dropping from 60 to 50 degrees in water temperature can be the difference between a lifelong disfiguring disability – possibly death – and a bad scald. The hotter the water, the quicker it will deliver a serious, full-thickness burn. This is where the epidermis and dermis – the skin’s outer and inner layers – are destroyed, and possibly the muscles and tissue below.

A full-thickness burn occurs within:

• Less than a second, at 70 degrees
• Within five seconds, at 60 degrees
• Within five minutes, at 50 degrees

Why are burns from hot tap water especially hazardous?

The biggest danger of hot tap water scalding is it typically affects more surface area of the skin. The classic, horrifying example is a bath accidentally heated to a dangerous temperature. For this reason, young children and the elderly are especially vulnerable. Some important facts to remember:

• In Australia, it is a legal requirement that all new and replacement hot water systems have bathroom tap water not exceeding 50 degrees. In Victoria, for child care centres, schools and nursing homes, the maximum temperature is 45 degrees.
• Senior-aged Australians living in older houses, with hot water systems installed prior to regulated safe temperatures, are especially at risk.
• Nearly all tap water burns that require hospitalisation occur in the home, specifically the bathroom. This is why the 50 degree-temperature for tap water rule applies to bathrooms only, not to kitchens or laundries.
• For young children, scalds from hot tap water make up nearly eight per cent of hospital admissions.

Does the hot tap water in my kitchen and laundry need to be 50 degrees?

Legally – in Victoria – no, as scalding from tap water most often occurs in the bathroom. For somewhere like a hospital or hotel, with industrial-sized dishwashers and washing machines, it’s not always practical to have controlled low-temperature hot water.

In the home, however, the risk is greater. The popularity of mixer taps – one handle for both hot and cold, means it’s terribly easy for a curious child to badly scald themselves at your kitchen sink. If you have young children or other vulnerable household members, the safest option is to lower the hot water temperature for all household taps. Remember the difference between five seconds (60 degrees) and five minutes (50 degrees) for a full-thickness burn.

Where does the tempering valve go? Are there different types?

The typical place for a tempering valve is right near the hot water storage system. There are different kinds of tempering valves, and depending on your source of power and the size of your storage system, a plumber can assess which one is right for your home. The types of tempering valves are often distinguished by their cap colour, most commonly:

• Electric or gas-powered water storage systems – blue or yellow
• Gas-powered only – green
• Extra-large water storage systems – black
• Solar and heat pump water storage systems – orange

Can I install or adjust a tempering valve myself? Or ask a handyman?

No. Tempering valves must be installed – and adjusted – by a licensed plumber. Trying to do so yourself is literally playing with fire – in the form of scalding hot water – and presents a significant risk to your personal safety. You are also legally responsible for any injuries an unlicensed worker that you hire might suffer.

How long does a tempering valve last?

The typical lifespan of a tempering valve is around eight years. If you notice your hot water tap is immediately running hot, it’s time to call a plumber.

My hot water system doesn’t have a tempering valve

If you have a hot water tank but no tempering valve, it’s likely you have an older style home, built before regulations were introduced. For safety reasons, it is strongly recommended you have one installed as soon as possible.

You might also consider upgrading your hot water system completely – it’s worth remembering that Victoria, like most other states in Australia, offers a rebate for replacing old hot water systems with safer models (See additional info: https://www.victorianenergysaver.vic.gov.au/save-energy-and-money/victorian-energy-upgrades/save-with-these-energy-efficient-products/hot-water-systems).

Tempering valves are essential safety components for your home and a simple but vital way to protect vulnerable members of your family. To keep your home safe, call or email the experts at Andrew J. Robertson Plumbing today.