Explore this post with your favourite AI tool:
Share this article with AI tools to summarise, remember, or explore the content further.
Legionella is a bacteria that causes the pneumonia-like illness Legionnaire’s Disease. The bacteria thrives in warm temperatures and low oxygen levels. It works its way into the lungs through the inhalation of water droplets that are contaminated with legionella.
And, it is more common than you think.
Where is legionella most likely to be found?
Legionella bacteria is a naturally occurring microscopic single-celled organism found in natural water systems such as streams, rivers, reservoirs, lakes and ponds. However, it can also be found in man-made water systems too. All water systems can be at risk of breeding legionella, so it is important for all employers and landlords to stay vigilant and check their water tanks and supply regularly.
Legionella is more commonly found in the water supply of older, public buildings such as hospitals, restaurants, hotels or offices. According to the Health and Safety Executive (HSE), the most common places where legionella can be found include purpose-built water systems, cooling towers, evaporative condensers, hot and cold water systems, spa pools, humidifiers, air washers, showers and ornamental fountains.
How can you minimise the risk of legionella?
There are a number of measures you can take to manage legionella in your business or property.
We’ve put together a helpful checklist to get you started…
- Step 1 – Legionella Risk Assessment
As a first step, we would advise the employer or duty holder to arrange for a competent or suitably qualified person to undertake a legionella risk assessment. Conducting a water risk assessment is essential in order to fulfil your legal obligations and protect the health and safety of those who may be at risk of exposure to legionella. An assessment should be thorough and identify any potential sources of exposure to legionella and determine the necessary precautions to prevent or control the risk of exposure.
- Step 2 – Remedial Works
Once you have received your legionella risk assessment and identified the risks, you need to work through the list of these risks to reduce or remove them completely. This could, for example, include cleaning out any water tanks that have sat dormant for a long period of time or implementing regular temperature checks.
- Step 3 – Take Water Samples
According to the HSE guidelines, water samples should be analysed for legionella periodically to demonstrate that bacteria counts are acceptable. We would recommend that this is done at least quarterly, and it needs to be carried out by a ‘competent person’. The HSE describes a ‘competent person’ as someone ‘with the correct qualifications, experience and training for the task to be completed’.
- Step 4 – Water Logbook
Create a water logbook to record and monitor any water checks and to assign roles and responsibilities to ensure your water testing and legionella risk assessments are always carried out when they are due, as a matter of process, and don’t get forgotten about.
This doesn’t need to be a physical book. It can be an online record. Whatever format your water log may take, it is important that it is communicated to staff so they know where to find it, what information to record and when it needs to be done.
- Step 5 – Weekly Flushing
Most taps are used weekly if not daily, which helps to keep water moving and difficult for bacteria to settle and grow. Stagnation is arguably the number one cause of legionella and in commercial settings, many outlets – such as office showers, changing rooms and accessible toilets – are rarely used, if at all.
All infrequently used outlets should be flushed out every seven days, or twice a week in the healthcare industry, to ensure water does not stagnate and encourage legionella growth. Outlets should be flushed until a stable and compliant temperature is reached.
- Step 6 – Monitor Temperature Monthly
Legionella bacteria can multiply at between 20 and 50°C. It’s most favoured temperature to thrive is 37°C (body temperature), which is why it can be dangerous to humans once contracted, causing illnesses such as legionnaire’s disease, pneumonia, Pontiac fever, and common cold and flu.
Water temperature needs to be taken regularly to ensure it remains consistent. It also helps to determine any potential areas of stagnation or risk.
Temperatures are required to be taken from all heat sources and the sentinel points of a water system. Sentinel points are the monthly temperature points at the nearest and furthest outlets of each water system. For example, taking the sentinel points from a cold-water storage tank would consist of taking the temperature from the nearest tap to the tank and the furthest away. For heat sources, this means taking the temperatures nearest and furthest from all heat sources. This may be a cylinder, electric water heater, boiler or otherwise.
7. Step 7 – Quarterly Descaling
Limescale is a great source of nutrients for legionella. Limescale can be found anywhere in water systems where there is hard water. The UK suffers from hard water due to the chalk limestone earth below the ground that finds its way into our reservoirs that supplies our mains water. Therefore, all outlets should be dismantled, cleaned, and descaled to remove the presence of limescale. This includes taps, spray heads, tank cleaning, showerheads and hoses.
8. Step 8 – Six Monthly Expansion Vessel Flushing
An expansion vessel is a small white, blue, grey or red tank. The white, blue and grey colours are there to identify water system expansion vessels and the red is to identify heating system expansion vessels. Each vessel includes a rubber diaphragm that goes across the middle, where the bottom half of the vessel is filled with water and the top half with pressurised air. When water is heated, it may expand as much as 4%. The expansion vessel allows this expanded water to flow. Guidelines outline that the expansion vessel must be flushed every six months to remove stagnant water from the vessel and relevant pipework.
9. Step 9 – Six Monthly Filter Servicing
A filter’s job is to cleanse water of impurities and allow for good quality water to pass through. By doing this, the filter inevitably becomes dirty itself. Most manufacturers recommend that a filter should be replaced or cleaned every six months.
10. Step 10 – Annual Cold Water Storage Tank Inspection
Coldwater storage tanks can easily end up carrying foreign bodies, such as insects and other animals, and are prone to sediment, biofilm from stagnation, and bacteria. Therefore, it is vital to monitor and test tank conditions and water quality regularly. This needs to be annually at the very least.
11. Step 11 – Annual Cylinder Inspections
Hot water cylinders are subject to continual heat changes that may increase the risk of legionella through non-compliant temperatures. They also require temperature gauges, pipe insulation, and should be purged periodically to remove any internal limescale, debris, or sediment.
12. Step 12 – Annual Combination Water Heater Inspection
A combination water heater consists of a cold-water storage tank on top, feeding the hot water cylinder below. Therefore, both the tank and cylinder inspections and servicing must take place annually.
13. Step 13 – Annual TMV Service
Thermostatic mixing valves (TMV) – blending valves that mix the hot and cold water to reduce the risk of scalding – should be serviced at least once a year as these filters are prone to blocking with limescale and sediment. A TMV service should include temperature calibration, failsafe testing, cleaning and disinfection of TMV parts.
14. Step 14 – Annual Water Softener Servicing
Manufacturers recommend that water softeners should be serviced annually to check levels of dissolved oxygen and provide technical guidance. This often includes a regeneration process where backflow is created to remove any bacteria within the water softener system.
15. Step 15 – Annual Water Testing/ Legionella Sampling
It is recommended that legionella sampling or a legionella risk assessment is undertaken at least annually to meet regulations. The number of water samples required will depend entirely on your water system. For example, samples should be taken from dead legs or areas of stagnation, cold water storage tanks, and all sentinel points to provide an accurate overview of water quality and the water system’s condition.
For more advice on legionella and legionella risk assessments, contact our team on 01604 936508 or info@acornsafetyservices.co.uk. You can also obtain a quote here.
