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It has happened to all of us, you turn on the hot water tap just to get a scalding flow of very hot water from the tap. The pain and sensitive skin that follows is the lowest level of injuries that are caused every year in the UK from overheated water, which in extreme cases leads to fatal injuries.

The Health and Safety Executive has issued new guidelines last autumn following a case of fatal burns due to scalding water. The new guidelines require all care homes to install temper proof thermostatic mixing valves to prevent such tragic injuries in the future.

The Scottish Building Standard already requires all new property developments and major refurbishments to install thermostatic mixing valves. Although not compulsory in the rest of the UK at the moment the Building Regulations in the UK are working towards adding it in a future update.

To reduce the risk of Legionella, it is required to keep hot water (for example within a hot water tank) at temperatures of between 60 and 65 degrees Celsius. At these temperatures it is believed that the Legionella virus does not survive. Nevertheless, water coming out of the tap at that temperature is too hot and should be mixed with colder water first.

Public buildings and communal hot water systems are predominantly in need of a TMV. This is due to the requirement of keeping the hot water at extremely high temperature all the way to the point of delivery to reduce the risk of Legionella.

The most vulnerable groups to scalding are the very young and the very old. Every year hundreds of children are admitted to hospital with burns from an extremely hot bath. Children have a very sensitive skin which gets burned very easily and leave a scar for life. On the other extreme, old people's skin is not as sensitive to hot water and their reactions are not as quick, especially when needing to turn off an extra hot water tap quickly. Another group that may be at risk are physically or mentally impaired individuals that suffer from slow reactions and slow response time.

Broadly speaking there are two groups of thermostatic mixing valves that are certified and approved for installation:

TMV2 are thermostatic mixing valves that are designed for domestic premises but are suitable for most other circumstances. A risk assessment must be undertaken to confirm whether the premises are used by disabled or vulnerable people.

TMV3 valves are engineered to tighter performance and provide better safety and quality. They are required in all installations in healthcare projects or on premises for disabled or vulnerable people (such as mentally or physically challenged people).

Manufacturers of thermostatic mixing valves recommend that they are installed only by qualified plumbers. The valves are positioned between the hot and the cold pipes to prevent the water coming out of the tap at an extremely high temperature. Most common TMVs are installed under the bath or under the hand basin for a simple installation. Most kits are sold with tailpieces which include isolation, a strainer and test points. Some kits have flexible connectors and isolating filter vales to deal with space limitations.