When it comes to ensuring the safety and efficiency of your hot water system, two critical components play a vital role: the tempering valve and the thermostatic mixing valve (TMV). While both serve to regulate hot water temperature and prevent scalding, they are distinct in their functionality, applications, and the level of precision they offer.

In this article, we’ll delve into what a tempering valve is, explore its importance in hot water systems, and clearly outline the differences between tempering valves and TMVs. Plus Plumbing is committed to helping you understand these essential components so that you can make informed decisions about your plumbing needs.

What Is a Tempering Valve?

A tempering valve is a temperature-activated mixing device that combines hot water from your storage tank with cold water to ensure that the water released from your taps is at a safe and consistent temperature, usually around 50°C. This mechanism is particularly important in residential settings where the risk of scalding, especially for children and the elderly, is a significant concern.

How Does a Tempering Valve Work?

The inner workings of a tempering valve involve a temperature-sensitive element that adjusts the mix of hot and cold water based on the pre-set temperature of the valve.

When hot water flows from the storage tank, the valve regulates the temperature by allowing cold water to mix with it, ensuring that the water delivered through your taps does not exceed the safety threshold.

This is particularly crucial as stored water must be kept at a minimum of 60°C to prevent bacterial growth, such as Legionella, but delivering water at this temperature would pose a serious risk of burns.

Types of Tempering Valves

Hot water tempering valves come in various types, each designed to work with specific types of water heaters, including those used in nursing homes.

• Blue Cap Valve: Typically used for electric water heaters, delivering water temperatures between 65°C and 75°C.
• Green Cap Valve: Suited for gas systems, including continuous flow models.
• Orange Cap Valve: Ideal for heat pumps and solar hot water systems where the incoming water temperature can be very high.
• Black Cap Valve: Commonly used for large capacity or low-pressure gravity feed systems.

These valves are essential in residential plumbing to ensure compliance with Australian Standards (AS3500), which mandate that water must be stored at 60°C to prevent bacterial growth but delivered at no more than 50°C to avoid scalding.

Regular Replacement of Tempering Valves

In New South Wales (NSW), it’s generally recommended to replace tempering valves every five years. Although this isn’t a strict legal requirement, it’s a widely accepted industry practice to ensure that your hot water system remains safe and efficient. 

Over time, tempering valves can wear out and lose their ability to accurately control water temperature. This can be particularly concerning in households with children or elderly individuals, where the risk of scalding is higher. 

Regularly checking and replacing your tempering valve as needed is crucial for maintaining hot water safety and compliance with industry standards.

What Is a Thermostatic Mixing Valve (TMV)?

A thermostatic mixing valve (TMV) is another type of mixing device, but with a higher level of precision and responsiveness than a hot water tempering valve.

TMVs are designed to maintain water temperature within a tighter range, typically within 1°C of the set temperature, making them ideal for environments where precise temperature control is critical, such as hospitals, aged care facilities, and schools.

How Does a TMV Work?

Similar to a tempering valve, a TMV mixes hot and cold water to achieve a desired output temperature. However, TMVs contain a more sensitive thermal element that reacts more quickly to temperature changes in water temperature and pressure.

This ensures that the water temperature remains stable even if there are fluctuations in the hot or cold water supply. This rapid response is particularly important in environments like nursing homes where vulnerable individuals might be at risk from sudden changes in water temperature.

Applications of TMVs

Due to their precision, TMVs are required in settings where safety is paramount. Australian regulations specify that TMVs must be used in facilities where the hot water temperature must be kept below 45°C, such as in healthcare buildings, aged care facilities, and childcare centres. TMVs are also commonly found in high-traffic public bathrooms, hotels, and shopping centres.

Difference Between Tempering Valve and TMV

While tempering valves and TMVs share the common goal of temperature regulation, several key differences set them apart:

• Accuracy: Tempering valves are accurate within a range of ±3°C, while TMVs maintain a tighter control, typically within ±1°C of the set temperature.
• Response Time: TMVs respond more quickly to changes in temperature and pressure than tempering valves, making them suitable for environments where sudden changes could pose a risk.
• Cost and Maintenance: TMVs are generally more expensive than tempering valves but are also more durable, often being repaired rather than replaced. Hot water tempering valves, on the other hand, tend to be replaced when they fail.
• Installation Requirements: Installing a TMV requires a plumber with a specific TMV licence due to the complexity and critical nature of these devices. In contrast, any licensed plumber can install a tempering valve.

Importance of Regular Maintenance

Both tempering valves and TMVs require regular maintenance to ensure they function correctly. For hot water tempering valves, this might involve checking the water temperature at the outlet and adjusting or replacing the valve as necessary.

TMVs require more frequent servicing, including the replacement of internal components like thermostats and O-rings every few years to ensure optimal performance in hot water storage. 

Regular maintenance is crucial not only for compliance with Australian Standards but also for ensuring the safety and comfort of your household or facility.

Inside Plus Plumbing

We recently received a call from a homeowner in the lovely Northern Beaches suburb of Collaroy, dealing with inconsistent hot water: Sometimes fluctuating hot, other times barely warm. After inspecting the system, we found that the tempering valve was over 5 years old and no longer functioning properly.

The homeowner hadn’t realized the importance of the tempering valve, thinking the fluctuating temperatures were just part of an old system. We replaced the faulty valve, and the hot water returned to a safe, consistent temperature immediately.

The homeowner was relieved, especially with young kids in the house, and appreciated our quick, thorough service and our honesty in not pushing for a new hot water system. Since then, we’ve returned to provide additional services for this client. Building trust and long-term relationships is our top priority at Plus Plumbing and something that we pride ourselves on.

Why Choose Plus Plumbing?

At Plus Plumbing, we understand the importance of safety and compliance with the plumbing code of Australia when it comes to your hot water system. Whether you need a tempering valve installed in your home or a TMV for a more specialised environment, our team of licensed plumbers has the expertise to ensure that your system operates efficiently and safely.

We take pride in offering tailored solutions that meet the specific needs of our clients, ensuring that you can enjoy hot water without the worry of scalding or bacterial contamination.

Conclusion

Understanding the roles and differences between a tempering valve and a thermostatic mixing valve is essential for anyone looking to maintain a safe and efficient hot water system. While both devices serve to regulate water temperature and prevent scalding, their applications, precision, and installation requirements vary.

At Plus Plumbing, we are committed to providing expert advice and professional installation services to ensure that your hot water system meets all safety standards and operates at peak efficiency. Whether you are outfitting a new home, renovating a bathroom, or managing a healthcare facility, Plus Plumbing is your trusted partner for all your plumbing needs.