• Lisamarie Lamb

Warmer Weather Is Coming: What Does That Mean For Legionella Bacteria?

The weather is changing. Now that the clocks have ‘sprung forward’ and April is upon us it won’t be long before we’re enjoying better temperatures (albeit in an isolated kind of way). This is where we and legionella bacteria have something in common; they like warmer temperatures too. In fact, they thrive in them, growing and breeding massively in water with temperatures between 20 and 50 degrees.

As a matter of course, cold stored water should be kept below 20 degrees and hot stored water should be over 60 degrees (although 50 degrees at the outlet should be sufficient). This is a great way to reduce the amount of legionella bacteria within your water systems, and is something that should be maintained all year round.

So what about warmer temperatures? What difference does that make?

Depending on the kind of water systems you have and the kind of building you are responsible for, it can make a big difference. Here’s why.

Maintaining The Temperature

One of the biggest issues with a rise in outside temperatures is that cold water storage tanks can become hotter too, especially if they are situated on a roof or within a roof space, and even more so if they are made from metal.



There isn’t much that can be done about this issue in terms of keeping the temperature down; the sun is always going to warm any loft space the water within the tank is going to rise above 20 degrees a lot of the time, at least during July and August, and possibly before and after that too.

The best option is to increase your water sampling rate. Make it every two weeks rather than once a month, or every week if you want to be completely thorough. This way, you’ll spot the legionella within the water sooner rather than later.

More Use

When the warmer weather comes certain water applications are going to see more use. Cooling towers and air conditioning units as well as hose pipes and swimming pools are going to get a lot more use during this time. A holiday camp might close for the winter and open up again in the summer, meaning the showers are now being used for the first time in months.

The problem is that there will be stagnant water lying dormant in all of these units and items. When they are used for the first time after a long time, that stagnant water, the ideal breeding ground for legionella bacteria, is going to spray out and be breathed in by any visitors, including potentially vulnerable people.


There is a simple fix for this. Weekly flushing of little used outlets including showers and hoses should be carried out throughout the year, even if the building itself is closed (especially if it is closed, in fact). Regular flushing means that legionella bacteria cannot reproduce as much and is literally flushed away making the water much safer when the outlets are used again.

Contact Assured Water Hygiene

The key to keeping your water systems safe for users is compliance throughout the year, no matter whether the building is in use or not. Legionella bacteria doesn’t care if people are using the showers or if the air conditioning unit is finally being switched on after a long, cold winter. But you should care if you are responsible for keeping the employees, visitors, and the general public within and around your building safe.

To find out more about your duties and to make sure you are complying with the regulations – or to request advice about how to do so including organising legionella awareness training if need be – please don’t hesitate to contact Assured Water Hygiene. Even in this time of COVID-19, your water treatment needs to be a priority.

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