How Climate Change and Legionella are Intrinsically Linked by Simon Bruce

October 31, 2024

As climate change becomes increasingly prominent in our modern world, businesses need to consider how it may affect health and safety. In recent years, there have been more and more links drawn between rising temperatures and the increased risk of Legionnaires’ disease.

Legionella bacteria, the causative organism of Legionnaires’ disease, needs certain factors in place to multiply, one of which is temperature (namely between 20 to 45°C). It is a ubiquitous organism, so is found in the natural environment such as rivers, streams and lakes where it is not normally a problem.

However, it is when it gets into engineered water systems where we tend to provide it with conditions to grow. As such, there is guidance from the Health and Safety Executive (HSE) for domestic hot and cold water systems which advises cold water temperatures to be below 20°C and hot water to be supplied at a minimum of 50°C (i.e. keep your hot water hot and your cold water cold).

Data from Public Health England shows cases of peaking during summer. Cases for 2020 were down compared to the 3-year mean, but this is most likely due to the COVID pandemic and the restrictions introduced.

The Met Office’s State of the UK Climate report for 2021 shows the ten hottest years in the UK since 1884 have all happened since 2002 and temperatures are continuing to rise. The Water Supply (Water Fittings) Regulations 1999 allows water companies to supply cold water up to 25°C so there is this potential grey area between 20 and 25°C.

So, what should you do if your incoming cold water supply is 20°C or above?

Firstly, you should look at your Legionella risk assessment and your water hygiene contractor should also be advising on what to do.

As for the HSE, in HSG 274 Part 2, they advise legionella sampling for;

‘water systems where the control levels of the treatment regime, eg temperature or disinfectant concentrations, are not being consistently achieved. In addition to a thorough review of the system and treatment regimes, frequent testing, eg weekly, should be carried out to provide early warning of loss of control. Once the system is brought back under control as demonstrated by monitoring, the frequency of testing should be reviewed;’

Temperature control has been the key mainstay for Legionella control within building hot and cold water systems, but the addition of alternative control strategies was introduced in 1998 with MISC 150; this is where alternative control strategies to temperature of chlorine dioxide or copper and silver ionisation were introduced.

Alternative control strategies have been further widened with HSG 274 Part 2 with chlorine and silver stabilised hydrogen peroxide added. The simplicity of the temperature regime is that you know instantly when temperatures are not right just by running a tap. When dosing a biocide, it is unlikely you will be able to tell how much is in your water without testing for it.

So, with temperatures rising, especially in the South, it is going to be harder and harder to keep your cold water below 20°C. The current guidance leaves you with 2 options if your cold water is 20°C or above.

The first is to carry out weekly Legionella sampling until the water cools to below 20°C. The second is to use an alternative control strategy with monthly Legionella sampling for at least the first year.

Ultimately, you should always refer to your legionella risk assessment; this is why it is so important to have an independent comprehensive assessment.

At William Martin, we’re here to make your water safety compliance as seamless as possible. We’re registered under the Legionella Control Association and we offer:

Strategic corporate compliance status audit and gap analysis
Legionella risk assessments of domestic water systems in compliance with L8, HSG274 and BS8580
Legionella risk assessments of cooling systems and towers
Water hygiene audits of all water system types, including drinking water
Sampling and UKAS accredited analysis for Legionella bacteria and other microbiological and chemical properties
Comprehensive Legionella control logbooks
Preparation of a written scheme of control procedures
Schematic drawings
Legionella awareness training for operators, supervisors and building managers

We’re on-hand to deliver expert Legionella advice so you have everything you need to elevate your water safety and achieve full compliance.

Want to reduce the burden of managing compliance alone? Get in touch with one of our experts today!

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At William Martin, we bring unparalleled health & safety expertise and powerful technology to the table. Whatever your sector and wherever you are, we give you the support you need to keep compliant, strong, and successful.

For all enquiries, please contact us or call our team on 0203 819 8829.