A thermostatic mixing valve (TMV) is a specially designed plumbing valve that carefully mixes hot and cold water to control hot water outlet temperatures to safe levels. TMVs are used in health,social care and education environments to protect people by reducing the risk of scalding from very hot water from showers, baths and wash hand basins.

Children and the elderly are particularly at risk from scalding from hot water with accident statistics showing that nearly 600 people suffered serious scald injuries in the UK each year. 75% of the victims of severe scalds were children under five years of age. Additionally, the figures also show that older people are at particular risk with those over the age of 65 accounting for almost two thirds of all fatalities in the UK.

Regular in-service testing of TMVs is essential to ensure they operate correctly, delivering safe water temperatures between 39°C and 43°C. This is the recommended temperature range for hot water outlets where a TMV is installed.

All TMVs should be tested and the results compared to those recorded during the original commissioning stage. Where there is no significant change to the outlet temperature (≤ 2°C) and the failsafe shut-off activates as it should, the TMV is considered to be operating correctly. However, if the water temperature has increased by more than 2°C or the failsafe does not work, a full TMV service plus recommissioning, or valve replacement will be required.

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There are currently 2 schemes in operation for the accreditation and usage of TMV valves TMV2 & TMV3