Thermostatic Mixer Valves (TMV)

TMVs accurately control water temperatures for bathing, showering and hand-washing. They maintain pre-set temperatures, even if water pressure varies when other appliances are used.

TMV Installation, Use and Maintenance

H2O Comply install, maintain and service all types of Thermostatic Mixer Valves (TMV). We offer servicing, fail safe testing, monitoring and adjusting to required temperatures. If you have a query concerning TMV's please feel free to contact us.

Why are Thermostatic Mixing Valves needed?

Thermostatic Mixer Valve

TMVs maintain pre-set water temperatures within safe parameters for bathing, showering and hand-washing. They help to prevent scalding, which can cause serious and even fatal injuries. Every year approximately twenty people die as a result of avoidable scalds caused by hot bath water, and a further 570 suffer serious scald injuries. Installation of TMVs is especially recommended in hospitals, care homes and schools and public buildings where the water is used by vulnerable groups such as the young, elderly or disabled.

We get many calls from clients surrounding Thermostatic Mixer Valves:

According to the TMV2 scheme, it is a requirement that all TMV2 approved valves shall be verified against the original set temperature results once a year. TMV3 valves must also receive a regular in-service test to check they are performing adequately. If they are not, the valve must be serviced. Thermostatic Mixer Valves are required to be checked once a year to ensure they are functioning correctly and maintaining the desired temperature. If the temperature of the water discharged by the thermostatic mixer valve fluctuates more than two degrees from the original setting a service will be required to rectify the temperature control.

To see whether TMV maintaince is necessary for your site or building, take a look at our TMV Chart.


Thermostatic Mixer Valves must shut down completely if the cold water supply is interrupted. This is called a "fail safe". Hot water temperatures are often used to control the growth of legionella bacteria. This can lead to a risk of scalding. In the case of a loss of cold water supply, the TMV unit needs to be self isolating.

The legionella prevention L8 guidance states that water must be stored at no less than 60 degrees and distributed at no less than 50 degrees, however where the risk of scalding has been identified TMV's are fitted to regulate the temperature at the outlets. The HSE advises of their use.

Our engineers are experts trained in the fail safe testing and servicing of all makes of TMVs.

Additional Information

Health and Safety Executive ACoP and Guidance L8:

"Temperature regime:- This is the traditional approach to legionella control. It is recommended that hot water should be stored at 60℃ and distributed so that it reaches a temperature of 50℃ within 1 minute at outlets. Care is needed to avoid much higher temperatures because of the risk of scalding. At 50℃ the risk of scalding is small for most people but the risk increases rapidly with higher temperatures and for longer exposure times. However the risk, particularly to young children, or the handicapped or elderly, and to those with sensory loss will be greater. Where a significant scalding risk has been identified, the use of TMVs on baths and showers should be considered to reduce temperature. These need to be placed as close to the point of use as possible."

Where installed, TMVs require regular servicing, generally twice per year. Where the valves installed are of the "fail safe" type (i.e. the valve will shut down if either the hot or cold water supply fails) then a failsafe test should be carried out to check the valve performance.

Health Technical Memorandum 04-01, published by the Department of Health, paragraph 9.49:

"Particular attention should be given to ensuring that pipework containing blended water is kept to the minimum. Generally, the downstream dead-leg should not exceed 2m, and the complete length of the spur should not exceed 3m."

The TMVA Code of Practice Section 4.2 'Group Mixing':

"The operation of one or more outlets should not affect the operation of any other outlet. When one valve is used to supply mixed water to a number of outlets the length of the pipe run and the volume of mixed water after the valve should be kept to a minimum. The maximum pipe run after the mixing valve should be such that the required mixed temperature, at the furthest outlet, should be reached within 30 seconds."