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Hot Water Risk Assessment - What you need to know!

by Water Hygiene Centre, on 17-08-2017
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Hot Water Risk Assessment - What you need to know!

The head of an estates team or building manager has a duty of care under health and safety law to the patients, staff and general public who use their site. Today we will discuss the importance of a hot water risk assessment and the importance of controlling temperatures on a healthcare site.

A hospital or healthcare setting such as a GP surgery or care home needs to be particularly diligent when it comes to managing the potential risks associated with their water systems. These sites are often densely populated and have a large number of at risk individuals who may at risk of scalding or injury.


Hot Water Risk Assessment

Guidance and legislation says that a Legionella risk assessment of a premises must be carried out when there is deemed to be a foreseeable health and safety risk. In the UK, this means that healthcare sites need to comply with the ACoP L8, HSG274 and HTM guidelines. These documents set out best practice recommendations in regards to things such as water temperatures, plant maintenance and Legionella sampling regimes.

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Alongside assessing the risk for legionella proliferation, the risk of scalding must also be investigated. All outlets delivering water should be assessed, with particular care given to full immersion outlets such as baths and showers. Due to the potentially large number of elderly, very young and people who are mentally or physically disabled, it’s important that high risk outlets are quickly identified and assessed.

A site survey should be carried out to cover all outlets onsite and this should be kept up to date taking into account evolving site usage. For Legionella control, hot water outlet temperatures are required to be 50°C within one minute of operation (55°C in healthcare buildings), however, temperatures above 41°C can result in scalding injuries.


How can we mitigate scalding risk?

Following the site risk assessment there are a number of ways you can help manage and reduce the risks associated with hot water outlets in a healthcare environment.

TMV 1TMVs (thermostatic mixing valves) should be considered at all outlets where there is deemed to be a significant risk of scalding. These allow the outlet temperature to be adjusted to within a more comfortable range to prevent the risk of scalding and injury.

There are three common types of TMVs available;

  • Type 1 – a mechanical mixing valve with or without temperature stop (i.e. manually blended);

  • Type 2 – a thermostatic mixing valve: BS EN 1111 and or BS EN 1287;

  • Type 3 – a thermostatic mixing valve with enhanced performance: HTM 04-01: Supplement. These are high performance mixing valves that are designed to operate and protect users from scalding under both high and low water pressure, temperature instability and thermal shutdown.

The Legionella risk assessment will help the Water Safety Group (WSG) consider the needs of the patient/service user and determine whether any of the above additional scalding protection devices is required.

Other ways to mitigate risk associated with hot water outlets include:

  • Supervision by competently trained staff when bathing vulnerable patients;

  • Ensuring doors to cleaning rooms are locked on wards that have children and vulnerable patients present;

  • Using appropriate hot water warning stickers on outlets that are not used for hand washing.

In areas such as neo-natal units and intensive care (ICU), where infection risk is at its highest, it may be suitable to install a TMV Type 1 due to the fact that patients do not use the outlets. The Legionella risk assessment should consider this and advise an appropriate course of action.

Conflict with Bacterial Growth

Installation of TMV’s increases the risk of bacterial growth due to their complexity and components.

Legionella flushing regimeWhen fitting TMVs the length of the pipe-run from the TMV to the outlet should be kept as short as possible and regularly flushed. This is due to the blended water in the pipe sitting at around 40°C-the ideal temperature for microbial growth. By keeping the connecting pipework short there is less surface area and volume of water for bacteria to grow.

The use of flexible hoses containing EDPM rubber should also be avoided due to the potential for microbial growth associated with this compound. Hard piping to the outlet is the preferred option, however in special circumstances, flexible hoses may be used, but only if they are WRAS Approved. Note that WRAS approval does not mean “Legionella proof”.

All imminent scalding risks observed during the assessment should be reported immediately, and action taken to reduce the risk to the users of the building.



The healthcare Water Safety Group has the responsibility to complete a scalding assessment and water hygiene risk assessment. The results of these surveys need to be carefully considered, with the appropriate expert advice sort if necessary to ensure compliance with current guidance.

A Legionella risk assessment will help duty holders balance the risk between infection and scalding.

If you have questions regarding the issues raised above or you would like to speak with one of our consultants please click here to get in touch.

Editors Note: The information provided in this blog is correct at date of original publication - August 2017. 

© Water Hygiene Centre 2019

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About the author

Water Hygiene Centre

The Water Hygiene Centre was established in 2009 to address the lack of independent water hygiene consultancy within the industry. From our humble beginnings, we have established ourselves as a market leader, helping clients identify and minimise the risk of waterborne contamination and disease, whilst improving compliance performance.

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