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Legionella Risk Assesment


A Legionella Risk Assessment is required under the Health and Safety at Work etc Act 1974 and the regulations outlined in ACoP L8. These regulations must be adhered to in order to ensure that you are compliant. It is the responsibility of the duty holder to ensure that a suitable Legionella risk assessment is regularly performed to consider, assess and manage the risk from Legionella bacteria and the BS 8580 is designed to enhance the management and control of Legionella bacteria in the risk assessment process.


What is legionnaires disease

Legionnaires Disease is a pneumonia like illness caused by the Legionella bacteria and can be fatal in up to 1 in 3 cases. The infection is caused by breathing in airborne droplets of contaminated water from showers, whirlpool spas, water spray, cooling towers, etc. The disease cannot be passed from one person to another. The majority of outbreaks are single cases and it affects men more commonly than women and also those with suppressed immune systems.

Legionella bacteria are found in the natural environment and may contaminate and grow in water systems such as cooling towers, hot and cold water systems, showerheads, spa baths and cooling towers. They survive low temperatures and thrive at temperatures between 20 - 45°C if the conditions are right. The bacteria are difficult to kill with chemicals if the system is not kept clean and so cleanliness is essential in controlling the risk.

The HSE guidance states that domestic hot water system should be set at up to 60°C and water should reach 50°C at discharge within one minute. If it is set above 45°C this reduces the risk but remember the water may cool while in the system, especially if it is not properly insulated. You will need to consider the risk of scalding for those who are vulnerable, thermostatic valves can reduce the risk.

Even if there is no storage of hot or cold water in the system and the hot water system temperature is set above 45°C a risk assessment is still necessary, but straight forward. There can be other factors which increase the risk of Legionnaires Disease e.g. dead legs, shower heads or long runs of pipe work which contain warm water. You can reduce the risk by proper design, maintenance and operation of the system.


Premises with high and low risks

Risks are low for instantaneous water heating systems.

Humidifiers, air conditioning plant, pools, whirlpool spa baths and indoor fountains are potentially high risk areas, so ensure the manufacturer's instructions are provided to tenants, are followed and they are serviced regularly.


What is the Landlord's/Employer's responsibility?

There is a duty to assess the risk of exposure and if need be implement appropriate control measures.

You must consider the risks from legionella that may affect anyone you employ and any members of the public, tenants and guests, and take suitable precautions. The responsible person should record the risks and precautions and review the assessment from time to time.


What happens if the landlord does not carry out his/her obligations?

The consequences can be serious. As a landlord/Employer you are legally required to manage properties so as not to expose employees, tenants, residents and visitors to risk. Heavy fines or even imprisonment can be imposed especially if someone were to unfortunately die. You can be prosecuted even if there is an exposure to risk without anyone actually becoming ill.



HSE leaflet explaining the duties 

of a Landlord/Employer

RESCOM legionella leaflet

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