As a part of my Health & Safety audits I will always ask my clients if they have had any legionella testing in their workplace.
Some clients are aware of these regulations and they sometimes have the report on hand to show me.
This is just perfect.
I then ask to see a copy of the report and check that weekly/monthly maintenance checks are being carried out.
There have been many issues with people being infected and some have even died due to legionella bacteria being in the water supply.
While Legionnaires’ disease is a relatively rare disease, outbreaks and sporadic cases continue to occur worldwide. Outbreaks can occur in various settings, including workplaces, healthcare facilities, and hotels.
The latest figures reveal there were 254 confirmed cases of Legionnaires’ disease in the U.K in 2023.
While the disease is potentially fatal, the good news is that harmful bacteria causing it can be removed by correctly maintaining water systems. Also, employers and landlords have a legal duty to do so and protect the health of people in their buildings. It is a key part of any water hygiene regime.
When and where do you find Legionella bacteria?
Legionella bacteria are most commonly found in water that meets one, or all, of the following three conditions:
- When the water is maintained between 20–45°C
- When the water contains nutrients
- When the water is stagnant
Legionnaires’ disease is contracted when people breathe in tiny water droplets in the air that contain Legionella bacteria. It is a type of pneumonia that can prove fatal, especially for at-risk populations, including the elderly, people with compromised or weakened immune systems, smokers, and alcoholics.
Legionella bacteria can also cause Pontiac fever, a mild flu-like illness with symptoms including fever, headaches and muscle aches.
Legionella bacteria are most likely to be found in:
- Atomisers
- Hot water heaters
- Cooling towers
- Wet air conditioning plants
- Whirlpool or hydrotherapy baths (e.g. hot tub)
- Showers
- Domestic hot and cold water systems
- Dead legs or low use areas
What are the first steps in preventing Legionella bacteria?
The first step is to appoint a competent person to assess the risk of Legionella bacteria growth in their building’s hot and cold water systems. Each business and building is different; therefore, the person responsible needs to understand how their unique systems work. The responsible person(s) will need to have completed Legionella training in order to be able to manage the system appropriately.
How often should Legionella testing be carried out?
The Legionella Risk Assessment should highlight the risk in your building and therefore when and how often you should test. However, if there is doubt over its findings – or if any procedures employed are ineffective – Legionella testing should be considered to be carried out weekly until the system is back under control.
When the results are evident or the procedures show effective results, it is safe to reduce or remove testing.
Seasonal variations and changes in water system usage patterns may also impact the risk of Legionella and determine when more testing may be needed.
For example, in the warmer months, cooling towers and air conditioning systems operate more frequently, creating conditions that favour Legionella growth. And if water systems experience extended periods of shutdown during winter or low-demand periods, stagnant water can also encourage more Legionella bacteria growth. Regular monitoring and timely testing will help you identify and assess potential risks.
How to test for Legionella bacteria
When inspecting water systems, there are several visual warning signs indicating a higher risk of the presence of Legionella bacteria, including:
- Corrosion – Corroded pipes, fittings or valves provide a breeding ground for biofilm formation, which can harbour and protect Legionella bacteria from disinfection methods. Rust-coloured water or the presence of flakes and rust particles are indications of corrosion.
- Scale – The accumulation of scale provides a favourable habitat for bacteria, including Legionella, to colonise and proliferate. Visual signs of scale include white or off-white deposits on faucets, showerheads or internal plumbing.
- Sediment – The presence of sediment such as dirt, debris or particulate matter can be a potential source of nutrients and support the growth of Legionella bacteria. Brown or cloudy water, or visible particles in the water, can indicate the presence of sediment
There are also several ways of testing for Legionella bacteria. The technology is rapidly changing, and each method has its own positives and negatives. The merits of each one should be explained in depth by a water treatment professional who can offer advice based on the requirements of your building and the type of water system in it.
Using temperature control to monitor and control Legionella
Another way to detect places that potentially contain Legionella bacteria is to test water temperature. While physically testing is necessary to ensure public safety, as always, prevention is the best cure. The best way to do this is to control water temperature, as the bacteria only grow to levels that can become dangerous between 20–45°C.
- Hot water storage cylinders (calorifiers) should store water at 60°C or higher
- Hot water should be distributed at 50°C or higher (thermostatic mixer valves must be fitted as close as possible to outlets, where a scald risk is identified)
- Cold water should be stored and distributed below 20°C
The temperature for water storage cylinders should be checked in accordance with the risk assessment, but this is likely to be every month, and cold water tank temperatures should be checked at least every six months. Also, ‘sentinel’ outlets, which are the closest and furthest from each tank or calorifier, should be checked for their monthly distribution temperatures.
Why rapid detection is important
Managing the risks of Legionella bacteria is key to protecting the people’s lives inside your buildings, and it is also a legal requirement.
Making sure that your building has a risk assessment and has regular Legionella control regimes in place will help to avoid outbreaks of Legionnaires’ disease.
