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Legionella is a common but deadly pathogen that grows in stagnating water systems in as little as a few weeks or months.
Inhaling airborne Legionella from aerosols can result in severe pneumonia, so UK businesses must prevent and protect their workforce and customers from exposure.
This guide examines Legionella, what it is, where it grows, and how to implement a prevention and detection program.
💡 Key contents
- What is Legionella?
- Ideal conditions for Legionella growth
- Legionella outbreak case studies
- Legionella regulations
- Legionella water management program
What is Legionella?
Legionella is a water-borne bacteria that causes a severe type of Pneumonia called Legionnaires’ disease when inhaled through contaminated aerosols.
It can grow in any place where water stagnates for long periods at room or warm temperatures.
Legionella-borne water must be disturbed and aerosolised to spread and cause infections, as it must be inhaled to be dangerous.
💡 Drinking water contaminated with Legionella is usually considered safe, but since it is associated with stagnating water, it may contain other pathogens.
Legionnaires’ disease
Legionnaires pneumonia must be taken seriously as it may require hospitalisation for the infected and can be fatal if not treated promptly, especially in vulnerable populations such as the elderly or the sick.
It is no joke: five hundred people in England catch Legionnaire’s disease every year, killing around one in ten!
While infection is uncommon, it is most typical in hotel guests, hospital patients, elderly in care homes, employees at poorly maintained office buildings, construction work, and public facilities with high amounts of water aerosols such as spas and swimming pools.
Ideal conditions for Legionella growth
Legionella bacteria love water stagnation, warmth and protection. They thrive in unoccupied water systems, typically indoors and in summer. Here are the details:
| Factor | Description |
|---|---|
| Temperature | Optimal growth occurs between 20°C and 45°C, which include both water at room temprature and heated water. |
| Stagnant Water | Stagnation promotes biofilm formation, which protects bacteria from disinfectants. |
| Nutrient Availability | Organic matter, scale, and sediment provide nutrients for growth. |
| Biofilm Presence | Biofilms offer a protective environment and nutrients. |
| pH Level | Growth is favoured in water with a pH between 5.0 and 8.5 - a range in which British water infrastructure lies within. |
| Sediment | Sediment can harbour bacteria and provide nutrients. |
| Scale and Corrosion | These can protect bacteria from disinfectants and offer a nutrient source. |
| Aerosol Generation | Systems that generate aerosols, like showers and cooling towers, can spread bacteria. |
| Inadequate Disinfection | Ineffective disinfection allows bacteria to survive and multiply. |
| Surface water | Surface water can have higher initial contamination, so any system that uses or disturbs this later is higher risk. |
Places where Legionella grows and spreads
The perfect conditions for Legionella growth are found in many places in any building’s water systems, but not all of them necessarily create the aerosols needed for infection. Here is how Legionella growth, spread and infection occur in different components of a business’ water system:
| Components | Legionella Growth? (Y/N) | Airbourne Legionella spread? (Y/N) |
|---|---|---|
| Aerators | Y - Can accumulate biofilm | Y - Aerosols generated during use can spread bacteria in the air |
| Centrally-installed Misters | Y - Warm, stagnant water in misters can support bacterial growth | Y - Mist generated can spread bacteria into the air |
| Cooling Towers | Y - Provides ideal warm, moist environments for bacterial growth | Y - Aerosols generated by the cooling towers can spread bacteria in the air |
| Decorative Fountains | Y - Warm, stagnant water can promote Legionella growth | Y - Aerosols generated by water spray can spread bacteria |
| Electronic and Manual Taps | Y - Warm water and biofilm formation support bacterial growth | Y - Aerosols generated during use can spread bacteria in the air |
| Expansion Tanks | Y - Stagnant water can support bacterial growth | N - No direct aerosolisation |
| Hoses | Y - Stagnant water and biofilm formation support bacterial growth | N - No direct aerosolisation |
| Hot and Cold Water Storage Tanks | Y - Stagnant water and biofilm formation can promote bacterial growth | N - No direct aerosolisation |
| Ice Machines | N - Cold temperatures do not support Legionella growth | N - No direct aerosolisation; bacteria spread through melted ice water |
| Infrequently Used Equipment, incl. Eyewash Stations | Y - Stagnant water supports bacterial growth | Y - Potential for aerosolisation during use |
| Medical Devices (e.g., CPAP machines, hydrotherapy equipment, bronchoscopes) | Y - Warm, stagnant water can support bacterial growth | Y - Aerosols generated during use can spread bacteria |
| Nonsteam Aerosol-generating Humidifiers | Y - Warm, stagnant water can support bacterial growth | Y - Mist generated can spread bacteria into the air |
| Pipes, Valves, and Water Fittings | Y - Stagnant water and biofilm formation support bacterial growth | N - No direct aerosolisation |
| Showerheads | Y - Warm water and biofilm formation support bacterial growth | Y - Aerosols generated during use can spread bacteria in the air |
| Tap Flow Restrictors | Y - Can accumulate biofilm and stagnant water | N - No direct aerosolisation |
| Water Filters | Y - Can accumulate biofilm | N - No direct aerosolisation |
| Water Heaters | Y - Warm temperatures (20-50°C) promote Legionella growth | N - No direct aerosolisation |
| Water-hammer Arrestors | Y - Stagnant water can support bacterial growth | N - No direct aerosolisation |
Historical Legionella outbreaks in the UK
Now that you understand the ideal conditions for legionella growth, spread and infection, here are some real-life UK case studies in which Legionella outbreaks have occurred:
| Year (Click for Source) | Location (Industry) | Mechanism of Outbreak | Cases (Deaths) | Description | Consequences |
|---|---|---|---|---|---|
| 2002 | Barrow-in-Furness (Public building) | Contaminated air conditioning system | 180 (7) | Linked to the air conditioning system in a council-run arts centre. | Barrow Borough Council fined £125,000; individual employees received fines and community service. |
| 2003 | Hereford (Industrial) | Contaminated cooling tower | 28 (2) | Outbreak traced to an aerosol plume from a cooling tower at a vegetable packing plant. | Company fined £100,000. |
| 2006 | London (Leisure) | Spa pool at a flower show | 3 (0) | Cases linked to exposure at a spa pool display at the Chelsea Flower Show. | No prosecutions; tighter controls at public events. |
| 2012 | Edinburgh (Industrial) | Contaminated cooling tower | 95 (4) | Outbreak linked to industrial cooling towers in the city. | Companies involved fined a total of £225,000. |
| 2015 | Staffordshire (Healthcare) | Hospital water system | 5 (1) | Outbreak occurred in a hospital, traced to the water system. | Hospital fined £200,000. |
| 2017 | Stoke-on-Trent (Hotel) | Spa pool | 3 (0) | Linked to a spa pool in a hotel, affecting guests and staff. | Hotel fined £75,000. |
| 2019 | Braintree (Commercial) | Contaminated water system in a supermarket | 9 (1) | Outbreak linked to the water system in a supermarket. | Tesco fined £8 million. |
| 2020 | Bristol (Care home) | Contaminated water system | 10 (2) | Outbreak in a care home, affecting elderly residents. | Care home fined £300,000; management received training. |
Legionella regulations
‘Health and safety’ and ‘Hazardous Substances’ regulations tackle preventing and managing Legionella at business premises.
The most pertinent regulation is the Health and Safety Executive (HSE) Approved Code of Practice (ACoP) L8: “Legionnaires’ disease: The control of legionella bacteria in water systems”, which provides immediate practical advice and legal requirements.
According to this document, the key requirements for all UK businesses are as follows:
| Key Requirements | Description |
|---|---|
| Risk Assessment | Identify and assess sources of risk, such as water systems that could harbour legionella bacteria. Should be conducted initially and reviewed at least annually, or whenever there are changes to the water system or its use. Applies to all businesses with water systems. |
| Control Measures | Implement measures to control the risk of legionella, including water treatment and regular cleaning. Specific measures may include maintaining water temperatures outside the range of 20-45°C, regular flushing of outlets, and using biocides. Applicable to all businesses with water systems. |
| Monitoring and Record-Keeping | Regularly monitor water systems and keep records of the control measures in place. Water temperature checks should be done monthly, with system inspections every 3 to 6 months. Applies to all businesses with water systems. |
| Training | Ensure that staff are trained and aware of the risks and control measures related to legionella. Training should be refreshed at least annually, and whenever there are updates to procedures or personnel changes. Applies to all businesses with water systems. |
| Review and Update | Periodically review and update the risk assessment and control measures as necessary. Reviews should be conducted at least annually, and whenever there are significant changes to the water system, its use, or if there are any incidents. Applies to all businesses with water systems. |
Compliance with Legionella regulations
The Health and Safety Executive, with the support of local authorities, is in charge of enforcing Legionella regulations on UK businesses. Non-compliance can lead to legal action, fines, business closure, and even imprisonment for severe breaches, leading to a significant outbreak. See our case studies for some examples!
Well-regulated industries such as the healthcare, hospitality, and industrial sectors generally show higher compliance rates, while smaller businesses often face challenges due to limited resources. Construction sites can also be at higher risk due to the temporary nature of their business water connections.
Legionella water management program
A water management program is essential for businesses seeking to ensure compliance with Legionella regulations.
It’s essentially a plan to implement risk assessments, control measures, monitoring, training and reviews to keep up with any regulation changes. Here is a step-by-step overview of how to get started:
1. Assemble a water management team
Assemble team “Anti-Legionella”, made up of representatives from facility management, engineering, maintenance, infection control (for healthcare facilities), and safety. Make sure the team is familiar with your specific water system and has ample technical knowledge.
2. Take a full inventory of your water system
The team’s first responsibility is to have a clear overview of the water system to identify key areas of concern as well as accessible areas to set up controls for monitoring, testing, etc.
This includes making flow diagrams of both potable and non-potable water systems, as well as portable water equipment such as hoses and pumps which are sometimes left out unchecked.
Here are some examples:
- Water entry pipes
- Water heating systems
- Graywater systems
- Cooling towers and water heating systems
💡 Make sure every floor level is considered and any system that uses water has been listed.
3. Risk assessment, control, monitoring and training
Taking inventory is essentially like doing the heavy lifting. Your team of experts will intuitively have an idea of the riskiest components, where and how best to control them and where and how often to monitor the water system.
We cover each of these in more details in this table.
💡 It’s important for your staff to receive training, as they can help identify potential risks that were previously overlooked, such as stagnating water, and biofilms.
3b. Testing for Legionella
You will need to test your water supply for Legionella and other pathogens as part of your regular control measures and monitoring to ensure the safety of your employees, guests, patients, or contractors.
To test for Legionella, your experts will collect water samples from the designated control points. The detailed sampling and lab methodologies used are detailed in the Health and Safety guidelines in our regulations section.
4. Establish a Legionella emergency action plan
No matter how thorough your controls and monitoring, there is always a chance Legionella has entered and established somewhere in your water system.
Even changes outside your control like works in the mains pipes outside of your property can change your water pressure and send previously free flowing areas of your water system into stagnation for enough time for Legionella to form.
In any case, you need to establish both a:
- Response plan: Create a clear plan of action for when Legionella is detected, including notification procedures and corrective measures.
- Remediation steps: Outline specific steps to remediate contaminated systems, such as hyperchlorination or thermal disinfection.
5. Review and update your plan
Finally, you need to ensure your periodically review your entire Legionella setup and update it to incorporate new methods or technologies that could facilitate your job, such as smart monitoring and automated alerts.
6. Document and communicate all activities
Finally, document and communicate all of your water management procedures, as this is essential for proving compliance with regulations.
This includes written evidence of all the above steps.
Legionella detection and prevention for businesses – FAQs
Our business water experts answer commonly asked questions on Legionella detection and prevention for businesses in the UK.
How common is Legionella in the UK?
Legionella is relatively common in the UK, especially in the man-made water systems listed here. This includes cooling towers, hot and cold water systems, spas, and showerheads, just to name a few.
While exact prevalence rates can vary, following Legionella regulations closely is essential to control its presence and prevent outbreaks of Legionnaires’ disease, of which there are about 500 cases every year in the UK. See our case studies for significant outbreaks.
How much does it cost to test for Legionella?
The cost to test for Legionella in water can vary depending on the type of test, the number of samples, and the laboratory performing the analysis. Generally, the cost ranges from £50 to £200 per sample, with basic culture tests being the least expensive and advanced methods like PCR testing being the most costly. Additional costs may include site visits, sample collection, and reporting fees unless this is done in-house!
Is it safe to drink water with Legionella?
Legionella primarily causes infection by inhaling contaminated water droplets, which can occur during activities like showering or within spas.
Ingestion (drinking) poses a lower risk, but vulnerable populations, such as those with weakened immune systems, should avoid exposure. Ensuring water systems are regularly tested and properly maintained helps minimise any potential risks.
Does boiling water kill Legionella?
Yes, boiling water kills Legionella bacteria. Boiling water for at least one minute effectively eliminates Legionella, making the water safe for consumption and other uses. This method is particularly useful for ensuring water safety in domestic settings or during outbreaks.
Does AquaSwitch have any other guides?
AquaSwitch can help save you money on your business water bills. Use our business water comparison service today and save thousands.
We hope this guide on Legionella detection and prevention was helpful to you. Here are three more guides we think may be of interest to you:
- Flood Planning For Businesses
- Guide to planning for water interruption
- A guide to water meters: Everything you need to know.
- Ultimate guide to Business water suppliers
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