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Why Do I Need A TMV or Tempering Valve?

Every week, our clients ask us why we must install a TMV or tempering valve to their hot water system. The simple and straightforward answer is that the law mandates it. However, we would like to emphasise that the underlying reason is the safety of the occupants.

A TMV or tempering valve is an essential safety feature that reduces the risk of scalding. This is especially important in storage-type gas, electric, solar, and heat pump systems where the water is stored at high temperatures, typically between 60°C and 75°C. Understanding that a severe hot water burn can occur in just one second when the water is delivered at 60°C or higher is crucial. Hot water burns like fire because of the following reasons:

At 60°C, a severe burn can happen in 1 second.
At 55°C, a severe burn would take 10 seconds.
At 50°C, a severe burn would occur after 5 minutes.

Therefore, it is clear that a TMV or tempering valve is essential in preventing scalding accidents, especially for children, older adults, and people with disabilities who may be more vulnerable to hot water burns. Therefore, installing a TMV or tempering valve is not only complying with the law but also a responsible action towards ensuring the safety of your household or building occupants.

What is a TMV or Thermostatic Mixing Valve?

A TMV or thermostatic mixing valve is a device responsible for mixing hot and cold water together to provide hot water delivery at a consistent temperature. The TMV achieves this by accurately regulating the temperature of the water delivered to your tap.

When we install your TMV, we set the temperature to deliver hot water at a consistent temperature of either 45°C or 50°C, depending on the specific application. For example, in aged care or childcare facilities, the temperature is set at 45°C, while in all other bathrooms, the temperature is set at 50°C.

In common areas for aged care or childcare, a TMV is mandatory to ensure the occupants’ safety. TMVs are very accurate and responsive to fluctuations in incoming water temperatures, maintaining the temperature to within 1°C of the temperature that it was set at during installation.

The temperature regulation accuracy in a TMV is achieved through a thermally sensitive element that expands and contracts in response to the temperature fluctuations of the incoming hot and cold water. This expansion and contraction control the temperature by adjusting the amount of cold water that mixes with the hot water.

In addition to accurately regulating water temperature, a TMV has an added safety feature that shuts down if cold water flows become too low, preventing hot water at temperatures of 60°C or higher from being delivered. This provides an additional layer of safety, ensuring that the water delivered to your tap is always at a safe and consistent temperature.

why we are required to install a TMV or tempering valve
This photo illustrates a TMV installed in a duplex unit to regulate all hot water from the Rinnai instantaneous gas hot water unit at 45°C where the occupant is in a wheelchair due to multiple sclerosis 

What is a Tempering Valve?

Like a TMV, a tempering valve’s primary function is to mix hot and cold water to provide a consistent water temperature at your tap.

A tempering valve is a simple three-way valve that is temperature actuated to mix hot and cold water. Most tempering valves come preset at 50°C, and during installation, we test them by measuring the temperature of the water from your hot taps in the bathroom.

Tempering valves are commonly used in residential homes as a one-off valve for the hot water service. Compared to a TMV, a tempering valve is slower to respond to temperature fluctuations and will deliver water to within 3°C of the temperature it was set at during installation.

While a tempering valve may not provide the same level of accuracy and responsiveness as a TMV, it is still an effective and essential safety feature in preventing scalding accidents. By providing a consistent water temperature, a tempering valve helps ensure that hot water delivered to your tap is at a safe and comfortable temperature.

Call Whywait Plumbing  to install a TMV or tempering valve
This photo illustrates that the handyman who illegally installed this hot water system did at least attempt to install a tempering valve; however, it is non-compliant as it has been connected with flexihoses which ultimately burst and required Whywait Plumbing to completely repipe the system and lodge a Form 4 compliance certificate.

Which Hot Water Safety Valve do you Require?

The Plumbing Code of Australia in AS/NZS 3500.4:2018 provides specific guidelines for water temperature control in various settings. For example, section 1.11 of the code outlines that to prevent the growth of legionella bacteria, water should be stored at a temperature of no less than 60°C. Furthermore, for specific settings such as healthcare, aged care, early childhood, schools, and nursing homes, heated water should not exceed 45°C for the aged, sick, children, or people with disabilities. For all other situations, heated water should not exceed 50°C.

As plumbing professionals, we are obligated to comply with the requirements outlined in AS/NZS 3500.4:2018 when installing temperature control devices. While a TMV may be more expensive to install initially compared to a tempering valve, it has a longer lifespan and is more accessible for servicing and replacing working parts. On the other hand, a tempering valve is typically replaced when it stops working, as it is not easy to service or replace parts.

In Queensland, any work performed on a TMV or tempering valve is reportable to the QBCC, and a compliant Form 4 must be submitted. We recommend that you always demand a copy of your Form 4 for your protection. It’s essential to ensure that any work performed on your hot water system complies with the necessary standards and guidelines to maintain the safety and comfort of the occupants.

The Paramount Importance of Safe Hot Water

In the complex realm of plumbing and water systems, it’s easy to overlook the subtle components that play a monumental role in our safety. The TMV or Tempering Valve stands as a silent sentinel, diligently working to ensure that our hot water usage is safe, preventing potential scalds and burns.

As we’ve unravelled throughout this discussion, these valves aren’t just a luxury but a necessity for every household. They bridge the gap between comfort and safety. In a world where the unexpected can happen in the blink of an eye, having a reliable TMV in place offers more than just regulated hot water – it provides peace of mind.

Ensure your hot water system is equipped with a functioning TMV or tempering valve and embrace the assurance of safety it provides.