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.
In autumn 2007 the Health and Safety Executive has introduced new directives for care homes. According to the new directive they have to install thermostatic mixing valves and make them temper proof. This latest development follows a tragic case of a fatal injury from scalding water.
Scottish Building Standards already include a requirement to install thermostatic mixing valves on all new property developments and major retrofit projects. The rest of the UK is not currently requiring this, but the Building Regulations body is reviewing this issue at the moment.
When storing hot water inside a domestic hot water cylinder, the requirement is to keep the water at a temperature of between 60c to 65c. At this level it is believed that Legionella virus does not survive. It is, however, important to note that at such a high temperature the hot water must be mixed before exiting the taps to reduce the risk of scalding.
TMVs are particularly important in public buildings or properties with communal water heating systems. Hot water regulations in the UK require water to be kept at high temperature throughout the system (up to the point of delivery) to reduce the risk of Legionalla.
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.
There are broadly two types of thermostatic mixing valves that are suitable for installation and certified:
TMV2 kits are mostly used for domestic installations. However, they are also suitable for most other properties. It is required to undertake a full risk assessment to review if there are disabled or vulnerable people on the premises.
TMV3 kits are required in healthcare premises and properties for disabled or handicapped people. TMV3 systems are designed with tighter tolerance levels, thus ensuring better safety levels and more accurate mixing performance, better protecting the users.
Most manufacturers of thermostatic mixing valves recommend qualified plumbers for the installations of their kits. For a qualified plumber, the kits are easy to install between the hot and the cold pipes to ensure effective mixing action. Most kits are designed for a simple installation under the bath or under the sink and include several important components. At typical kit includes tailpieces with isolation, a strainer and test points. To handle installation in limited spaces, there are kits with a flexible connector and isolating filter valve.
About the Author
Tal Potishman, member of Heating Central, writes content about
efficient central heating systems,
St Albans plumbers, boilers, heat pumps and solar thermal systems. He specializes in helping save money by advising on efficient heating.
