TMV Servicing (Thermostatic Mixing Valve)

A Thermostatic Mixing Valve (TMV) is a valve that blends hot water with cold water to ensure safe,  constant water temperatures (typically between 38 °C and 46 °C depending on outlet use) to showers, baths and water outlets, preventing scalding.

The storage of water at high temperatures (60°C) prevents the likelihood of Legionella bacterial growth, however this presents a risk to the end user in the form of a scald risk, where susceptible individuals could be scalded. Susceptible users include the young, venerable and elderly. The blended water downstream of TMVs may provide an environment in which legionella bacteria can multiply, thus increasing the risks of exposure.

The use and fitting of TMVs should be informed by a comparative assessment of scalding risk versus the risk of infection from legionella. Where a risk assessment identifies the risk of scalding is insignificant, TMVs are not required and as such if in place should be removed. The most serious risk of scalding is where there is whole body immersion, such as with baths and showers, particularly for the very young and elderly, and TMVs should be fitted at these outlets.

Where a risk assessment identifies a significant scalding risk is present, eg: where there are very young, very elderly, infirm or significantly mentally or physically disabled people or those with sensory loss, fitting TMV’s at appropriate outlets, such as hand washbasins and sinks, is required.

Where TMV’s are fitted,  the following risk factors should be considered:

  • TMV’s should be incorporated directly in the tap fitting, and mixing at the point of outlet is preferable;
  • where TMV’s are fitted with low flow rate spray taps on hand washbasins, the risk is increased;
  • TMV valves should be as close to the POU as possible to minimise the storage of blended water;
  • where a single TMV serves multiple tap outlets, the risk can be increased;
  • where TMV’s are designed to supply both cold and blended water, an additional separate cold tap is rarely needed and may become a low use outlet.

Where a scalding risk is assessed as low (eg: where healthy users immerse their whole body), type 2 TMV’s that can be overridden by the users are required by building regulations. Where a scalding risk is considered significant (eg: where users are very young, very elderly, infirm or significantly mentally or physically disabled or those with sensory loss) then type 3 TMV’s that are pre-set and fail-safe should be provided (but are required at healthcare premises) and should be checked regularly to ensure they are fail-safe if the cold water supply pressure is interrupted.

HSG 274 part 2 guidance requires that a risk assessment is undertaken to confirm whether the TMV fitting is required, and if not, removed. Where TMV’s are needed, the units should be inspected, cleaned, descaled and disinfected with any strainers or filters associated with TMV’s being removed and cleaned. This will maintain protection against scald risk. TMV’s require regular routine maintenance carried out by competent persons in accordance with the manufacturer’s instructions.

TE Compliance Ltd can assist your business by providing the following services;

  • TMV risk assessment
  • TMV servicing, strip down and fail safe checks
  • TMV replacement

Following completion of these services you will be provided with a comprehensive and professional report detailing follow up remedial actions.

““Total Environmental Compliance Limited are my preferred compliance partner for the provision of works relating to the control of Legionella Bacteria on my contracts within the FM business. They have worked with KIER for a number of years and we have found them to be professional, supportive and we have built a great working relationship over this time. Recently I have appointed TE Compliance to undertake TMV servicing across my portfolio of buildings which includes Care Homes and Schools. We were very impressed by their diligent and comprehensive approach, the end report is user friendly, clear and concise. Following the servicing of the TMV’s a large number of units required replacement, pleasingly TE Compliance stepped in to complete this quickly and efficiently. I would have no hesitation in recommending Total Environmental Compliance Ltd.”

Sean Whelan – Senior Contracts Manager

For further information contact us on 0151 257 9302 or via email at