Proactive prevention

Legionnaires’ disease remains a public health concern, with government data showing a rise in UK cases since COVID-19, for example, 604 cases in England and Wales in 2023 compared to 337 cases in 2020.

Despite this growing number of cases, mortality rates have decreased significantly. The Chartered Institute of Plumbing and Heating Engineering (CIPHE) attributes this rise in cases following the pandemic to the reactivation of dormant water systems, improper maintenance during lockdowns, as well as changes in public behaviour.

The CIPHE has warned that these figures underscore the importance of staying informed and taking proactive measures to prevent the spread of Legionella: “Increased awareness of respiratory diseases on the part of patients and healthcare professionals following the COVID-19 pandemic are likely to have contributed towards earlier detection and improved survival rates – a vital reminder of the importance of such factors, and why CIPHE continues to highlight the issue so frequently.”

Invisible danger

Although Legionella bacteria are widely found in natural water systems, such as rivers and ponds, the conditions are rarely right for people to catch the disease from these sources. However, outbreaks of Legionnaires’ disease occur from exposure to Legionella bacteria growing in purpose-built systems, such as cooling towers, evaporative condensers, hot-and-cold-water systems and spa pools, where the water is maintained at a temperature high enough to encourage growth of the Legionella bacteria.

Legionella bacteria can cause Legionnaires’ disease, a potentially fatal form of pneumonia – as well as less serious conditions like Pontiac fever and Lochgoilhead fever – from inhaling small droplets of contaminated water.

People at higher risk from the disease’s effects include those over 45; smokers and heavy drinkers; those suffering from chronic respiratory or kidney disease; diabetes; lung and heart disease; and anyone with an impaired immune system.

“While healthy individuals can recover quickly, older adults, smokers and people with weakened immune systems are at higher risk of severe complications or even death,” warns Kevin Wellman, CEO of CIPHE. “Given the rising statistics, it is crucial for homeowners, building managers, and businesses to understand the risks and take appropriate preventive actions.”

Assessing the risk

In the UK, legislation places a duty on building owners and those in charge of premises to manage the risks to health associated with water systems.

The Health and Safety Executive’s ACOP L8 (Legionnaires’ disease: The control of Legionella bacteria in water systems) states that Legionella risk assessments should be reviewed regularly and whenever there is a change of circumstances that could affect the risk. It also outlines responsibilities for employers and those in control of premises, detailing how to conduct risk assessments, implement control measures like water temperature management and cleaning, and maintain records. Adherence to ACOP L8 is crucial for legal compliance and protecting public health. “Risk assessments should identify potential hazards, such as pathogenic organisms including Legionella pneumophila and Pseudomonas aeruginosa, scalding, chemical contamination and disruption to the water supply,” explains Charlie Brain, senior consultant and authorising engineer (Water) at the Water Hygiene Centre. “They should consider all foreseeable events that may arise during the supply, storage, delivery, maintenance and use of the water.

“The assessment of risk is not an isolated exercise; it is an ongoing process and should evolve alongside the building’s usage. According to ACOP L8, the assessment should be reviewed whenever there is a reason to suspect it is no longer valid.”

Design control

Careful design of hot-and-cold-water systems plays a vital role in preventing Legionella outbreaks. For example, high-profile cases that have been well publicised, such as contaminated water at the Queen Elizabeth University Hospital in Glasgow.

The issues found here have led to a public enquiry, with the findings showing that proper investment into the design, installation and commissioning of water systems is necessary. According to the Water Hygiene Centre, there are many aspects to consider when it comes to design:

Water usage: Engaging with end users at the design stage can make a significant difference in managing water systems in the future. There is no point in installing several outlets that will likely never be used, as they will need an ongoing regime of flushing to manage, or capital expenditure to remove.

Correct components: All components installed on water systems should be made of approved materials (such as WRAS or Kiwa-approved products). However, there are several components that could be installed on a water system that will actually increase the risk of Legionella bacteria forming.

Even with approved materials, many will raise the Legionella risk once installed. An example of this is thermostatic mixing valves (TMVs), which are typically installed to prevent scalding. The presence of these devices increases the Legionella risk as they blend hot and cold water to a suitable temperature for Legionella growth and have surfaces within them that can harbour biofilm. Therefore, they should only be installed when absolutely necessary.

It is essential to conduct a scalding risk assessment during the design stage of the project so that TMVs are not installed where they are not needed, to reduce Legionella risk where possible. It’s important to ensure that there is only one TMV device per outlet to prevent future issues and remedial work. Problems can occur when a TMV is fitted on the supply to a TMT (a tap with a built-in TMV). This act of double blending causes water temperature and flow issues, and doubles maintenance requirements.

Preventing heat transfer: Properly insulating pipework will help prevent heat transfer, but it is also essential to keep hot and cold pipework away from each other to further minimise heat transfer. No insulation is perfect, but avoiding cold pipework running on top of hot, by keeping them in separate risers where possible, will help prevent heat gain in the cold-water systems. Also, keeping cold water pipework away from sources of heat gain, such as radiant panels, will help keep the water cold.

Monitoring and testing

The HSE’s HSG274 – Part 2 says that “Legionella monitoring should be carried out where there is doubt about the efficacy of the control regime or it is known that recommended temperatures, disinfectant concentrations or other precautions are not being consistently achieved throughout the system.” Therefore, sampling for Legionella should be part of a defined strategy, with the complexity of the system taken into account.

Typically, the circumstances when monitoring for Legionella would be appropriate include the following:

• water systems treated with biocides where water is stored or distribution temperatures are reduced
• water systems where the control levels of the treatment regime, e.g. temperature or disinfectant concentrations, are not being consistently achieved
• high-risk areas or where there is a population with increased susceptibility, e.g. in healthcare premises, including care homes
• water systems suspected or identified in a case or outbreak of legionellosis.

Where monitoring for Legionella is considered appropriate in hot- and-cold-water systems, taking of samples should be carried out in accordance with the British Standard BS7592 – Sampling for Legionella bacteria in water systems: A Code of Practice. Samples must be taken and analysed by a UKAS-accredited laboratory.

“The presence of a confirmed positive Legionella count (or counts) strikes fear in all those involved with water safety,” says Brain. “Whether the positive count is warranted or could have been avoided is a moot point, and action must be taken to investigate and resolve the root cause in the immediate and longer terms. We can be sure in the knowledge that the more Legionella sampling we undertake, the increased likelihood there is of obtaining a positive result. In essence, we can predict that potential positive results will occur.”

Positive response

Appropriate measures should be taken following a positive result to protect the occupants of the building where the samples were taken. These appropriate measures need to have been agreed by the Water Safety Group and then feature as part of the agreed protocol.

Some examples of measures that would be taken to protect the occupants include:

• informing local and other staff of the issue, convening a review of the issue in an appropriate Water Safety Group
• undertaking a safe Legionella flushing regime and keeping good water hygiene records
• fitting a point-of-use filter(s) as a short measure to keep water in use and turning over
• removing the outlet(s) from use
• undertaking a similar or more extensive re-sampling programme in the short term.

“To establish the root cause of a positive count, the prescriptive process for the protocol must include a systematic elimination of potential issues, including the sampling process itself, i.e. has the process been compromised, thereby causing the positive count, and do we need to undertake a competency review of those who’ve taken the sample, its handling, any transportation concerns and review the accreditation of the lab,” says Brain.

“After this, we can investigate the water system. When receiving a positive Legionella sample result, the lab can issue an interim report with probable results and a final report. The culture method of analysis for water samples can take 10-14 days, during which time the lab will observe the samples and any bacterial growth. The lab can issue interim counts up to the final day of analysis, when a final report will be issued.”

FIND OUT MORE

For more detailed information on the HSE’s Approved Code of Practice and Guidance, visit: hse.gov.uk/pubns/books/l8.htm

The Water Hygiene Centre has published these useful blogs on legionella:

• waterhygienecentre.com/blog/htm04-01-water-healthcare
• waterhygienecentre.com/blog/hsg-274-part-1-2024

Practical steps to protect against Legionnaires’ disease

To combat this preventable illness, the Chartered Institute of Plumbing and Heating Engineering (CIPHE) provides comprehensive advice on the website. Key recommendations include:

• regularly cleaning and maintaining of water systems, particularly those in infrequent use
• keeping water temperatures within safe ranges: hot water should be stored at 60°C or above, and cold water should be below 20°C
• flushing unused taps and showerheads regularly to prevent water stagnation
• seeking professional help for water system inspections and Legionella risk assessments.

ciphe.org.uk/public/plumbing-health-hazards/legionnaires-disease

Technical guidance

HSG274 is a series of technical guidance documents that support the ACOP L8, providing comprehensive information on specific water systems and their associated risks, control measures and monitoring requirements. It is divided into three parts:

• Part 1 - Covers cooling towers and evaporative condensers.
• Part 2 - Focuses on hot-and-cold-water systems.
• Part 3 - Addresses other risk systems, such as spa pools. Additional guidance on Spa pools is available in HSG 282 - The control of legionella and other infectious agents in spa-pool systems and decorative water features.

HTM 04-01 2016; Part B – Safe Water in Healthcare Premises; Operational Management, offers guidance for healthcare environments. This document explains how correct governance is key to directing, managing, and monitoring activities to ensure they are aligned with current guidance and legislation, and to ensure compliance whilst ensuring that the safety of patients, staff and visitors is not compromised.

“Compliance with ACOP L8, HSG274 and HTM04-01 (and other relevant legislation) is crucial for maintaining a safe and healthy environment,” explains Brain.

“Understanding the basics of these guidelines empowers duty holders to effectively manage and control the risks associated with Legionella bacteria. By following the requirements and recommendations outlined in these documents, we can ensure the wellbeing of employees, visitors and the general public, while preventing the spread of Legionnaires’ disease.”