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How to prevent Legionella growth in warm weather

We’ve seen an upward trend in instances of Legionella in water sources. This heatwave is showing no signs of letting up, which we feel can only mean more legionella outbreaks.

Warmer temperatures increase the risk of bacteria growth, including Legionella for several reasons.  This is why it’s important to make sure you’ve assessed and controlled the risk adequately.

Temperature is one of the most important control measures for reducing the risk of Legionella. Keeping your cold water below 20°C and your hot water at over 50°C will prevent the bacteria from flourishing.  Legionella thrives at temperatures between 20°C and 45°C, especially where there are nutrients in the water, so when the weather gets hotter, as it is now, it’s important to take action.

Time to check and sample bodies of stored water.  Here’s some guidance on how to prevent Legionella growth in warm weather:

Check Water temperatures in hot and cold water systems for Legionella

HSE guidance states that you should check your water temperatures monthly. It’s good practice to check more frequently for Legionella growth in warm weather..  Check both hot and cold water taps, and check your tanks. Make sure to check at different points throughout the water system.

Check Air Conditioning and Cooling Towers for Legionella

Air conditioning systems and humidifiers are the perfect delivery mechanism for Legionella bacteria as they create and disperse a fine mist of water into the air. If this water is contaminated with bacteria, it goes straight into the lungs where it can cause Legionnaires’ disease.

Check Swimming Pools & Hot tubs for Legionella

Water hygiene measures are particularly important in large bodies of warm water such as swimming pools and hot tubs.  A planned programme of water testing, chemical dosing, cleaning and maintenance are necessary to ensure that pools are safe and clean.  

Be safe, get a Legionella Risk Assessment

All water systems should have an adequate Legionella Risk Assessment carried out on them, with special attention to be paid to systems that are more at risk of harbouring and spreading Legionella Bacteria. Legionella risk assessments should be carried out on systems that:

  • Have a water temperature of between 20-45°C
  • Store water, or re-circulate water in the system
  • Have contamination from rust, iron oxide sludge, organic matter or biofilms
  • Release water droplets, such as showers or cooling tower aerosols
  • Are used by people who are more susceptible to developing Legionnaires’ Disease

This includes a selection of systems such as:

  • Spa pools, swimming pools and hot tubs
  • Hot and cold water systems
  • Humidifiers, misters and wet scrubbers
  • Fountains and Water Features

Water Treatment Record Keeping

Keeping accurate records is incredibly important. Make sure it is clear which taps or tanks were checked each time, where they are, who checked them, when they were checked, and anything that wasn’t quite right and what was done to remedy it.

We’re experts in Legionella Risk Assessment and testing, if you’re unsure if you’re responsible for completing and documenting Legionella testing or are unsure which of your systems require a Legionella Risk Assessment, then get in touch with us today and we’ll be happy to provide you with the advice and recommendations you need to ensure you meet your legal obligations.