Legionnaires’ disease is a potentially fatal pneumonia caused by legionella bacteria.Infection is caused by breathing in small droplets of water contaminated by the bacteria.The disease cannot be passed from one person to another.
Legionella are widespread in the environment in water and may grow in hot and cold water systems. They survive low temperatures and thrive at temperatures between 20oc and 45oc if a supply of nutrients is present. The bacteria can be a risk if they are dispersed in water droplets such as from showers, spa baths and wet based air conditioning systems. In dwellings showers pose a potential risk of legionella, particularly if they are used irregularly.
Under health and safety law you have a duty to consider the risks from legionella that may affect your tenants, employees or members of the public and take suitable precautions to control the risks.
You must:-
If a risk is identified which cannot be prevented, proper controls must be introduced:
Water in the boiler should be kept at a minimum of 60oc and water at each outlet point should be above 50oc within a minute of running the water. (Thermostatic mixing valves for showers can prevent scalding)
Water should be less than 20oc and at each outlet point below 20oc within 2 minutes of running the water
Shower heads and hoses should be dismantled, cleaned and descaled at least quarterly
Any units not regularly used must be flushed through and purged to drain without release of aerosols, eg remove shower heads regularly.
Ensure that the tank is insulated with a closed lid
Hot and Cold Water Temperatures should be:-
If a hot water system feeding showers is newly installed or has been out of use for over 1 week, the water should be brought up to 60oc for 1 hour before being used. This should kill any legionella bacteria. Alternatively, a chemical biocide can be added for at least 3 hours then the system flushed through before use.See the Health and Safety Executive (HSE) for further advice and information