Tempering Valves and Thermostatic Mixing Valves (TMVs)
Hot water is an essential part of any home, especially during a Melbourne winter, but did you know that without temperature control, it can pose serious safety risks? In Victoria, tempering valves and thermostatic mixing valves (TMVs) are required by law for specific installations, ensuring safe water temperatures for everyday use. This guide will answer the question; What is a tempering valve? and explain the difference between both valves, how they work, and why they’re crucial for both residential and commercial properties.
What is a Tempering Valve?
A tempering valve is a device that blends hot and cold water to ensure a safe and consistent outlet temperature, typically set at 50°C for bathrooms and other outlets used by people, especially children or the elderly. The valve is installed between the hot water system and taps, regulating the temperature of water flowing from your hot tap to prevent scalding while maintaining a warm, comfortable water temperature.
Why is a Tempering Valve Required?
Victoria’s plumbing regulations require tempering valves in domestic installations to limit water temperatures. Here are the main reasons why:
- Safety Against Scalding: Hot water systems often store water at temperatures above 60°C to prevent bacteria growth (which can cause legionnaires disease), but water at this temperature can cause burns in seconds. Tempering valves reduce this risk by blending in cold water before it reaches your taps.
- Legal Compliance: In Victoria, tempering valves must be installed in new homes, renovations, and any situation where a hot water heater is replaced. Further situations where a tempering valve is required is listed below. Compliance helps ensure the safety of all building occupants.
- Energy Efficiency: Regulating water temperature also conserves energy by reducing the need to excessively reheat water.
What is Legionella?
When installing hot water systems and tempering valves, Plumbers need to work within the parameters of lowering the temperature setting to reduce the risk of scalding and save energy and increasing the temperature enough to decrease the risk of bacteria growth in the tank.
Legionella bacteria thrive in temperatures between 20-45°C, with their ideal range being 37-43°C. Australian plumbing regulations require water heaters (the hot water tank) to be set at a minimum of 60°C to prevent bacterial growth. At this temperature, 90% of Legionella bacteria die in just 2 minutes, and raising it to 70°C eliminates them almost instantly.
However also as per Australian plumbing regulations, a tempering valve must be installed on all hot water systems to ensure water that is heated up to 60°C must leave the tap at 50°C (to prevent scalding) and thermostatic mixing valves are also used in nursing homes and childcare centres. As 50°C is near the danger zone of 43°C, the valves must be regularly maintained by a plumber and flushed to ensure the bacteria doesn’t grow.
What is a TMV (Thermostatic Mixing Valve)?
While similar to tempering valves, thermostatic mixing valves (TMVs) offer even more precise control over water temperature, often required in healthcare, aged care, and childcare facilities where a stricter temperature regulation is needed. TMVs are generally more sophisticated and can maintain consistent temperatures even with fluctuating water pressures or temperatures.
Key Differences Between Tempering Valves and TMVs
| Feature | Tempering Valve | TMV (Thermostatic Mixing Valve) |
| Use | Domestic and light commercial | Hospitals, aged care, childcare, commercial settings |
| Temperature Control | Basic (±3°C) | High precision (±1°C) |
| Installation Cost | Lower | Higher |
| Maintenance | Simple; periodic checks recommended | More intensive; annual servicing often required |
Benefits of Installing a Tempering Valve
- Protects Vulnerable Users: Tempering valves are essential in households with children, the elderly, or anyone at higher risk of accidental burns.
- Compliance with Standards: Meeting regulatory standards helps prevent legal issues down the road, particularly if you’re planning any renovations or building work.
- Improved Comfort: Consistent, moderated water temperatures create a safer and more comfortable home environment.
Plumbing Code of Australia Requirements
The Victorian Building Authority (VBA) states the below information on their website:
To prevent scalding, the Plumbing code of Australia (PCA) requires the delivery temperature of water used for personal hygiene purposes (primarily bathroom taps) to be limited to a prescribed temperature for a specific type of building, these are:
- 45°C for early childhood centres, primary and secondary schools, and nursing homes or similar facilities for young, aged, sick, or disabled persons – In these situations, the water temperature must be controlled by a thermostatic mixing valve conforming with AS 4032.1, or thermostatically controlled tap conforming with AS 4032.4.
- 50°C for all other buildings. – In these situations, either a tempering valve conforming with AS 4032.1, or a water heater designed not to exceed 50°C may be used to control the water temperature. In the case of a water heater, it must be marked “this appliance delivers water not exceeding 50°C in accordance with AS 3498”.
- Note that restricting the delivery temperature in kitchens and laundries is optional.
When is a Tempering Valve or Thermostatic Mixing Valve Legally Required?
The Victorian Building Authority States that the requirement to limit certain water delivery temperatures applies to all new heated water installations. A new heated water installation includes:
- a heated water service installed on the premises or recreational vehicle for the first time; or
- an existing water heater that is replaced with a like-for-like water heater in the same location
- an existing water heater that is replaced with a different type of water heater in the same location
- an existing water heater that is relocated and reconnected to, some or all of the sanitary fixtures to which it was previously connected
- where more than one existing sanitary fixture is replaced with new similar fixtures; or
- an existing heated water service on the premises is altered or extended to serve additional sanitary fixtures. These requirements do not apply to the replacement of a water heater unit in the same location where the original installation did not require a temperature control valve, for example:
- Where a water heater in a Class 1 dwelling which was built prior to 5 August 1998 and has not been altered since, is replaced with a water heater in the same location.
Do Tempering Valves Need Maintenance?
Yes, tempering valves require periodic maintenance to stay effective. Over time, these valves can wear down, reducing their accuracy or causing malfunctions that could lead to unsafe water temperatures. Scheduling a maintenance check every few years helps keep them in good working order.
What if I Don’t Want to Install a Tempering Valve in my Home?
If you’re unsure whether your current setup meets Victorian standards or want to know more about adding a tempering valve or TMV, contacting a licensed plumber is best. They’ll ensure your system is installed correctly and meets regulatory requirements for optimal safety and compliance.
Tempering valves play an essential role in maintaining a safe home environment, preventing hot water scalds, and ensuring water heaters function efficiently. Whether you’re renovating, building a new home, or simply updating your water heater, a tempering valve or TMV will be key to keeping your household safe and compliant. Please call McCarthy Plumbing Group to discuss your Tempering Valve and TMV requirements on 03 9931 0905.