TMV Servicing and Legionella

To prevent Legionella outbreaks, it is crucial to regularly maintain and monitor thermostatic mixing valves (TMVs). Following HSE guidelines, it is important to inspect and test TMVs on a regular basis to ensure they are functioning correctly and maintaining safe water temperatures. This will involve checking for leaks, ensuring proper calibration of the valve, and verifying that the water temperature falls within the recommended range. By conducting these maintenance tasks, the risk of Legionella contamination can be significantly reduced. Additionally, regular monitoring of water temperatures throughout the building can help identify any potential issues and allow for prompt action to be taken. By implementing a comprehensive maintenance and monitoring plan for TMVs. Businesses can significantly reduce the risk of Legionella growth and protect the health and safety of their employees and customers.

The Importance of TMV and Legionella Control

Thermostatic mixing valves (TMVs) are essential in preventing the growth of Legionella bacteria in water systems and ensuring the safety of individuals using the water. These valves regulate the temperature of water by blending hot and cold water together, creating a safe temperature range of 38°C to 46°C to prevent scalding. However, it is important to note that the blended water downstream of TMVs can create an environment where Legionella bacteria can multiply. To address this, it is recommended to regularly inspect and clean TMVs to minimise the risk of exposure to bacteria.

To prevent Legionella breeding, it is also advised to keep hot water sources, such as hot water cylinders, at a temperature of 60°C. However, this high temperature can pose a scalding risk, especially in areas where vulnerable individuals are present, such as accessible toilets. To ensure safe use, it is necessary to mix the hot and cold water temperatures. This is particularly important for individuals who may not be able to quickly move away from the water to prevent burns. And for those who have conditions that prevent them from sensing temperature changes. By utilising thermostatic mixing valves, the risk of Legionella growth can be effectively controlled. While maintaining safe water temperatures for all users.

Key Factors to Consider for TMV and Legionella Control when Fitting:


  • TMVs to be incorporated directly in the tap fitting, and mixing at the point of outlet
  • When low flow rate spray taps are installed on hand washbasins, there is an increased risk of legionella in TMVs.
  • TMVs is to have them located as near as possible to the point of use (POU). This will reduce the amount of blended water that needs to be stored.
  • When a single TMV (thermostatic mixing valve) is used to supply water to multiple tap outlets. There is an increased risk of legionella bacteria growth.
  • In cases where Thermostatic Mixing Valves (TMVs) are installed to provide both cold and blended water. There is usually no need for an additional separate cold tap. This is because the TMVs can supply the desired temperature water, eliminating the need for a separate outlet.

Understanding the Risk in TMV and Legionella: Scalding Risk vs. the Risk of Legionella

When considering water safety, there are two main concerns: the risk of scalding and the risk of Legionella infection. Scalding can occur when the water temperature exceeds 44°C at the outlet. To determine whether Thermostatic Mixing Valves (TMVs) should be used. A comparative assessment should be conducted, weighing the risk of scalding against the risk of Legionella infection. If the risk of scalding is low in a particular area, TMVs may not be necessary. However, in situations where there is a high risk of scalding, such as in baths and showers, especially for vulnerable individuals like the very young and elderly, TMVs should be installed. Additionally, if a risk assessment identifies a significant scalding risk for specific individuals. Such as those who are very young, elderly, infirm, mentally or physically disabled, or have sensory loss. TMVs should be fitted at appropriate outlets like hand washbasins and sinks.

The Importance of Understanding the HSE Guidelines on TMV and Legionella

According to guidelines from the Health and Safety Executive (HSE), there is a risk of scalding when the water temperature at the outlet exceeds 44°C. This risk is particularly high in facilities where vulnerable patients, such as the elderly, young children, and individuals with disabilities or sensory loss. Specially, when they will be exposed to the whole body immersions in baths and showers. While most people face minimal scalding risk when water is delivered up to 50°C at hand wash basins. Additional precautions may be necessary for vulnerable individuals who have access to baths or showers. In such cases, the installation of Type 3 Thermostatic Mixing Valves (TMV3) will be required to mitigate the risk of scalding.

The Importance of Regular Servicing for TMV and Legionella

Regular maintenance of thermostatic mixing valves (TMVs) offers several advantages. Firstly, it helps to identify and address any potential issues before they become major problems. As a result, this will save time, money, and inconvenience in the long run. Secondly, servicing ensures that the valves are functioning optimally, providing accurate temperature control and preventing scalding or freezing incidents. Additionally, regular maintenance extends the lifespan of the valves, reducing the need for costly replacements. By prioritising regular servicing, you can ensure the safety, efficiency, and longevity of your TMVs.

If a legionella risk assessment determines that fitting Thermostatic Mixing Valves (TMVs) is necessary. It is recommended to inspect, clean, descale, and disinfect the strainers or filters annually according to HSE guidelines. To maintain protection against scald risk, TMVs require regular routine maintenance performed by competent individuals following the manufacturer’s instructions.


What temperatures should a TMV be?

  • Basin – Set to 38-43°c
  • Showers and hair-wash facilities – Set to 41°c
  • Unassisted baths – Set to 41°c
  • Baths for assisted bathing – Set to 46°c
  • Bidet – Set to 38°c

Understanding TMV Servicing: What’s Included and Why it Matters

TMV servicing includes several important steps. First, a visual inspection is to be conducted to ensure that the correct TMV valve is installed in the appropriate location. Next, the temperature control should be checked and calibrated to ensure that the water to be delivered at the correct temperature. A fail-safe test should be performed to ensure that the TMV’s safety mechanisms are functioning properly in the event of a water supply failure. Finally, any strainers or filters are to be cleaned, descaled, and disinfected to maintain optimal performance.

Techright Environmental specialises in Legionella control and servicing of TMVs (Thermostatic Mixing Valves). Our experienced Legionella remedial team is well-versed in inspecting, cleaning, descaling, and disinfecting any strainers or filters associated with TMVs. Rest assure, we will provide you with a TMV certificate to ensure the safety and compliance of your systems.


Call us today for more information and prices on TMV Servicing