Legionella bacteria can easily proliferate in hot and cold water systems where conditions are right and appropriate controls are not in place. Employers and landlords responsible for building management have a legal obligation to have legionella controls in place. Through proper assessment, planning and prevention measures.
Legionnaires’ disease is a dangerous condition spread by inhaling microscopic droplets of water contaminated with the legionella bacterium. The bacteria lives in water, thrives in temperatures between 20 oC and 45 oC and grows fast where stagnation is able to occur and biofilm allowed to build up. The disease can be deadly for anyone, but it is particularly dangerous for those in high-risk groups such as the sick and elderly.
What is Legionella and why is it a concern?
Legionella is a naturally occurring bacterium commonly found in freshwater environments. However, when it enters artificial systems, such as plumbing networks, hot water tanks, or cooling towers. It can multiply rapidly under the right conditions, particularly between 20°C and 45°C.
When people inhale tiny water droplets containing the bacteria, it can lead to Legionnaires’ disease. Those most at risk include older adults, individuals with weakened immune systems, and people with chronic respiratory conditions.
Understanding how and where Legionella thrives is the first step toward keeping your water systems safe.
The importance of Legionella Risk Assessments
Under the Approved Code of Practice (ACoP L8) and HSG274 guidance, all employers, landlords, and duty holders have a legal responsibility to assess and manage the risk of Legionella within their water systems.
A Legionella risk assessment helps identify areas where bacteria could grow. This could be in stagnant pipework, inconsistent water temperatures, infrequently used outlets, and more.
By identifying these vulnerabilities, organisations can take proactive measures to reduce risk and ensure compliance with UK health and safety standards.
Temperature control: Your first line of defence
Maintaining the correct water temperatures is one of the most effective ways to prevent Legionella growth:
- Hot water should be stored at 60°C or above and distributed at 50°C or higher.
- Cold water should be kept below 20°C at all times.
Regular monitoring, logging, and calibration of temperature checks are essential, both for regulatory compliance and for early detection of potential issues. Consistent temperature management provides a simple yet powerful barrier against bacterial proliferation.
Designing water systems for safety and efficiency
Effective system design can greatly reduce the likelihood of Legionella developing. Good design principles include:
- Avoiding dead legs or redundant pipework
- Designing systems that are easy to inspect, clean, and maintain
- Maintaining good flow throughout the system to prevent water from becoming static
A well-designed system not only supports hygiene and safety but also reduces maintenance burdens and long-term operational costs.
Maintenance and record keeping
Preventing Legionella contamination is an ongoing process that requires routine maintenance and thorough documentation. Key activities include:
- Regular flushing of little-used outlets
- Cleaning and descaling taps, showerheads, and storage tanks
- Inspecting and servicing key components to maintain functionality
- Recording all maintenance, test results, and corrective actions
Designating a responsible person ensures accountability and helps maintain compliance with health and safety legislation.
How to respond to Legionella contamination
If Legionella contamination is detected, swift action is critical.
Thermal disinfection (raising water temperatures above 70°C) and chemical treatment using approved biocides are the most common remediation methods.
After any disinfection process, post-remediation testing should be carried out to confirm that the bacteria have been effectively eradicated. These steps will not only protect building occupants but also restore confidence in your water safety management programme.
Speak to an expert today
Controlling Legionella in hot and cold water systems is a vital part of maintaining safe environments across workplaces, residential buildings, and public facilities.
By prioritising proactive maintenance, temperature control, and robust system design, organisations can prevent outbreaks and ensure compliance with UK safety standards.
Get in touch today to discuss your Legionella risk management needs. Our specialists provide tailored assessments, monitoring solutions, and ongoing support to help you stay fully compliant and safeguard public health.
FAQs
Q: Why is controlling Legionella important in water systems?
Legionella can cause Legionnaires’ disease, a severe type of pneumonia. Controlling it protects public health, particularly for vulnerable individuals.
Q: What temperatures prevent Legionella growth?
Hot water should be stored at 60°C or above and distributed at or above 50°C. Cold water should remain below 20°C to inhibit bacterial growth.
Q: How can I assess Legionella risk?
Conduct a Legionella risk assessment following ACoP L8 and HSG274 guidance. Identify areas of stagnation, poor flow, and temperature inconsistencies.
Q: What maintenance practices are essential?
Regular flushing, cleaning, descaling, and maintaining accurate records are all crucial to prevent contamination.
Q: What should I do if Legionella is found?
Use thermal or chemical disinfection to eliminate the bacteria, followed by post-treatment testing to confirm the system is safe.
Q: How does system design impact Legionella control?
Good design limits stagnation, reduces dead legs, and ensures easy access for maintenance, all essential factors for effective Legionella prevention.
Q: Where can I train my team to self deliver risk assessments?
Marlowe Environmental Services offers dedicated specialist training courses through its training division.