Preventing Legionnaires’ disease

Legionnaires’ disease is a form of walking pneumonia caused by legionella bacteria that is commonly found in the built-in water systems of hotels, hospitals, office buildings, flats and houses. While the fatality rate of those infected ranges between 5 to 30 per cent, the disease is fatal in roughly 50 per cent of patients who go untreated.

As a landlord, you are obligated to follow the Control of Substances Hazardous to Health Regulations 2002 to ensure that the tenants living in your properties are protected against Legionnaires’ disease.

Ideal environments for the growth and spread of Legionella bacteria

The cooling towers, central air conditioning systems as well as the hot and cold water systems installed in your properties are just a small selection of the many ideal environments for legionella bacteria growth.

People contract Legionnaires’ disease by inhaling the contaminated airborne water and/or soil particulates that are dispersed through the air conditioning vents and/or water outlets. But some people are more susceptible to Legionnaires’ disease than others. Your tenants may be at a higher risk of contracting Legionnaires’ disease if they match the following profile:

  • Aged over 45 years
  • Smoke and drink heavily
  • Suffer from chronic respiratory or kidney disease
  • Have an impaired immune system

Conduct regular risk assessments of the various water systems in all of the properties that you own or manage in order to mitigate the risk of tenants developing Legionnaires’ disease.

Safeguarding against the risk of contamination and infection

As a landlord, there are six main risk-preventive measures that you can adopt to control the risk of legionella bacteria contamination:

  1. Perform regular quality testing of the water that is stored in the tanks. A water treatment company or consultant can perform the test. If you would prefer to do the test yourself, consult the HSE’s Legionnaires’ disease Technical Guidance found here
  2. Remove redundant pipework to ensure that water cannot stagnate anywhere in the system. When inspecting a property’s pipework, refer to the Water Fittings & Materials Directory ( to avoid materials that encourage the growth of bacteria
  3. Ensure that water tanks have tight seals so that no debris is able to contaminate the system
  4. Set temperature control standards of the calorifier to ensure that water is stored at 60 degrees Celsius
  5. Treat the water stored in tanks or other systems to limit or control the growth of micro-organisms
  6. For housing units, completely flush the water tank prior to letting the property

After adopting legionella prevention measures at your properties, inform your tenants of any additional responsibilities they must shoulder or procedures they must follow to continue mitigating their Legionnaires’ disease risk. These additional responsibilities may include:

  • Not adjusting the temperature on the calorifier
  • Regularly cleaning and disinfecting their shower heads
  • The risk of legionella bacteria growth is reduced with regular use, but you should still encourage tenants to regularly clean and disinfect their shower heads
  • Report any issues with the hot water, air conditioning or any other systems