How to prevent Legionella growth

If you use hot and cold water systems in your business, you need to pay extra attention to plumbing and water treatment, especially Legionella testing. Legionella bacteria are responsible for a wide range of illnesses, including the fatal Legionnaire’s disease, which causes 200-250 deaths annually in the UK.

Here is what you need to know about the causes and prevention of Legionella

What causes Legionella growth?

Legionella bacteria naturally occur in freshwater lakes and streams, but it can also get into a building’s water system. This is caused by factors such as:

Water temperature variations

This bacterium thrives where temperatures are between 20-45 degrees Celsius.


Biofilm is a layer of microorganisms such as bacteria, fungi and protists that grows on surfaces exposed to moisture. This slimy build-up eats disinfectant, creating a perfect breeding ground for Legionella.

pH fluctuations

Disinfectants only work if your water’s pH is between 6.5 and 8.5. That said, your water’s PH can quickly change due to chemicals, pollution and the presence of plant or organic material.


Stagnant water encourages the growth of biofilm and soaks up disinfectant much faster. Stagnation happens when water usage decreases or when certain fixtures go unused for a prolonged period.

How can you prevent Legionella growth?

Temperature control

Water temperature control is the primary method used to control Legionella growth. To do this, ensure that hot water is stored at 60°C or higher and cold water below 20°C. The bacteria cannot survive in temperatures above 60°C and is dormant in temperatures below 20°C.

Use the right amounts of disinfectants

Preventing Legionella growth requires you to maintain a certain level of disinfectant in your water. Therefore, your building’s water supply will need long-term supplemental disinfectants to prevent Legionella growth. Consider subscribing to our planned maintenance packages to ensure that your water’s disinfectant levels are boosted as required.

Take regular samples

The only way to know if your preventative measures are working is by conducting regular Legionella testing. In case your tests come back positive, you will be able to pinpoint exactly where the bacteria are growing and take the necessary measures.

At Brooktech Maintenance, we offer Legionella testing and plumbing and water treatment services, so contact us today and speak to an expert.


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