What is a Thermostatic Mixing Valve?
A thermostatic mixing valve (TMV) is a device that ensures water temperature is at a safe and comfortable water temperature level preventing people from burning themselves. Hot and cold water is blended as it passes through the valve on its way to the tap, ensuring it is at a safe temperature by the time it reaches the water outlet.
Hot water sources such as hot water cylinders should be kept at a temperature of 60oC in order to prevent bacteria such as legionella from breeding. As such, these high temperatures may scald the skin. Therefore it is necessary to blend the hot and cold water temperature to ensure safe use, particularly where vulnerable persons are present. This is important when it comes to accessible toilets and service user areas as some users are not able to move away from the water quickly enough to prevent burning. Others may have conditions where they cannot physically feel any temperature changes.
Children and the elder are particularly at risk from scalding from hot water with statistics showing that nearly 600 people suffered serious scalding injuries in the UK each year. And 75% of those scalded were children under five years of age. This is why Thermostatic Mixing Valve or TMV servicing is essential.
Scalding Risk in Temperatures
What temperature does scalding start for vulnerable people?
When it comes to scalding, the HSE states that – “There is a risk of scalding where the water temperature at the outlet is above 44°C. In certain facilities with ‘at risk’ patients this is especially so where there is whole body immersion in baths and showers of vulnerable patients, including the very young, elderly people, and people with disabilities or those with sensory loss who may not recognise high temperatures and respond quickly.” HSG 274 – p.2163
What temperature is scalding for most people?
“For most people, the scalding risk is minimal where water is delivered up to 50°C at hand wash basins and using hot water signs may be considered sufficient, where a TMV is not fitted. However, where vulnerable people are identified and have access to baths or showers and the scalding risk is considered significant, TMV Type 3 (TMV3) are required.” HSG 274 – p.2.164
What Type of TMV and Where?
“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 and TMV Servicing is not required.
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 burning 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 TMVs (thermostatic mixing valves) at appropriate outlets, such as hand wash basins and sinks, is required.” HSG 274 – p.275
Health Care Buildings
“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 TMVs 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 – infobox 2.3: Thermostatic mixing valves: TMV Servicing & Failsafe Testing
“Where a scalding risk is assessed as low (e.g. where healthy users immerse their entire body), type 2 TMVs that can be overridden by the users are required by building regulations.” HSG 274 – infobox 2.3: Thermostatic mixing valves & TMV Servicing
What temperatures should a TMV be?
Set to 38-43°C
Showers and hair-wash facilities
Set to 41°C
Set to 41°C
Baths for assisted bathing
Set to 46°C
Set to 38°C
Note – bath fill hot water temperature of more than 44°C should only be considered in exceptional circumstances where there are particular difficulties in achieving an adequate bathing temperature.
Temperatures as listed in – The HTM 04-01: Safe hot water in healthcare premises. Part A: Design, installation and commissioning practices (table 2 page 55)
How Often do TMVs Need Servicing?
“Where the risk assessment considers fitting TMVs appropriate, the strainers or filters should be inspected, cleaned, descaled and disinfected annually or on a frequency defined by the risk assessment, taking account of any manufacturers’ recommendations.” HSG 274 – p.2.164
Regular TMV servicing and maintenance check, temperature monitoring and failsafe testing is required to ensure your TMV’s perform at the NHS Model Engineering Specification Level. If a valve fails a TMV servicing and maintenance test, the valve must either be serviced in accordance with the NHS Model Engineering Specification, or if it can not be serviced it should be replaced.
Regular & on-going TMV servicing maintenance tests and failsafe testing should be carried out to demonstrate adequate thermal performance is being maintained. Get in touch to book your TMV servicing maintenance!
What is Included in TMV Servicing?
Review the installed TMV to ensure correct specification valve is installed where required.
Undertake temperature check and re-calibrate where required.
Ensure TMV failsafe mechanisms operate correctly to protect users in the event of water supply failure.
Clean, Descale & Disinfect
Clean, descale and disinfect any strainers or filters.
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How Does a TMV Mix Hot and Cold Water?
A TMV regulates water temperatures using a mixed water temperature system. Landowners with hot water outlets must ensure a TMV3 valve is fitted. This will result in the set temperature of the building’s water supply meeting the UK safety standards for water outlets. Moreover, isolating the cold water supply with regular failsafe testing to ensure reasonable water temperatures is required. This ensures the safety of vulnerable persons who could be affected by overly hot water temperatures.
What are the Health and Safety Regulations for Thermostatic Mixing Valves?
The set temperature for hot water outlets usage in social care services is between 39’c and 43’c or lower. When it comes to TMV health and safety regulations for hospitals, healthcare services and social care services, the primary means of controlling the growth of Legionella Bacteria in hot water systems is using hot water temperatures. Current guidance set by the Department of Health states that hot water used in social care services should be stored at a minimum of 60°C and used mixed with a cold water supply at a minimum temperature of 55°C. Regular TMV cleaning, descaling and disinfection is required by health and safety laws.
What are the steps in TMV Servicing and Maintenance?
Water quality standards must be maintained and regular valve components services must be conducted to ensure you are managing the risks of legionella correctly. Remedial works and services can be used to check the fine mesh of TMV3 Valves when you service TMV. Ensuring your water quality standards, safe water temperatures and safety standards are meeting the standards that the NHS sets is a necessity. TMV Water treatment also includes remedial work like cleaning, descaling and disinfection.
When and How Often do I need a Risk Assessment?
Under the Health and Safety at Work Act 1974 and in compliance with the Approved Code of Practice (ACoP L8, HSG 274), duty holders, including employers and those in control of premises, must ensure the health and safety of their employees or others who may be affected by their undertaking, this includes a legionella risk assessment.
Precautions must be taken to prevent, manage and control the risk of exposure to legionella. Including regular water treatment, maintenance & monitoring, water cleaning, temperature monitoring, descaling and disinfection. You can do this by undertaking the following: a legionella risk assessment by water treatment and engineering experts. Get a free legionella audit with us today!
Do uRisk Service my Area?
Yes, uRisk’s services are nationwide. Whether you have one or multiple water systems or sites. We service TMV & TMV3 Valves across the country. With qualified engineers offering remedial works & services scattered throughout the UK. Our offices are based in Hertfordshire which is a 30-minute train journey to London King’s Cross.
Why choose uRisk?
Over 25 years of water hygiene and legionella control experience.
Friendly and simple advice by phone, email & online at your convenience.
All staff are trained water hygiene consultants and engineers.
With engineers located all across the UK, we’re never too far away.
Our labs are UKAS approved providing you with quality assurance.
Your one stop shop for Legionella control, no need to go elsewhere.