Installers are being urged to 'get to know' their thermostatic mixing valves after a survey of more than 200 plumbers revealed that only 17% knew the difference between the TMV2 and TMV3 scheme.

The survey, carried out by Honeywell, also revealed that 86% would like to know more about Part G Building regulations and the different TMVs which are available.

All TMVs offer vital protection to people against scalding when showering, bathing and hand washing, by controlling the blend of hot and cold water which comes out of the tap. However, TMV2-approved valves and TMV3-approved valves offer different levels of protection, which are suitable for different applications.

TMV2-approval identifies valves suitable to prevent domestic scalding; while TMV3-approved valves, which offer a higher level of protection, are the only models considered suitable for NHS and healthcare applications.

Matthew Watson, water sales development manager at Honeywell, commented: “It is vital that plumbers and installers know the difference between these two TMV approved schemes and this survey has proved that there is a considerable gap in knowledge in this area.”

TMV3-approved valves are certified against the requirements of the NHS Estates document D 08, which covers mixing valves installed within healthcare properties. TMV3-approved valves can also be used in a domestic application so long as the pressure in the property is sufficient. For instance, the Honeywell TM200VP valve can be used on pressures from minimum 0.2 bar to a maximum of 10 bar, with a 2.5bar differential pressure between hot and cold.

TMV2-approved valves are tested against BS EN 1111 and 1287 as a minimum performance level and are only considered safe enough for domestic use. Typically, these valves work on pressures of between 0.1 bar to 5 bar. Honeywell recommends that installers always check the manufacturer’s product information to determine which valve to use.

The Building Regulations Part G3 were revised in April 2010. Section 3.65 covers the prevention of scalding and states: "The hot water supply temperature to a bath should be limited to a maximum of 48ºc by use of an inline blending valve or other appropriate temperature control device, with a maximum temperature stop and suitable arrangement of pipework."

This revision applies to baths in all newbuild, extensions of buildings or buildings with a material change of use.

It is the responsibility of the person in charge of the property to ensure all necessary steps are taken to prevent people being injured. On all domestic, commercial or institutional properties, a risk assessment should be carried out to establish how susceptible people are to the dangers of scalding. For this reason it is imperative that installers fit the right TMV-approved valves.

Honeywell has developed a series of FAQs, and a new Water Controls Guide booklet, to help offer guidance on which TMVs to fit in which application and a full product portfolio of all Honeywell TMVs for installers. For more information, please visit