Legionella Testing

Before considering carrying out a risk assessment you should familiarise yourself in particular with the following HSE publications:

Quick Guide to Legionnaire’s risk assessment including a free risk assessment form

Legionnaire’s disease: A brief guide for dutyholders –http://www.hse.gov.uk/pubns/indg458.pdf

Legionnaire’s disease Part 2: The control the relevant part of Legionella in hot and cold water systems


If you do not consider that you are competent then give the task to someone who is.

The risk assessment process

The practical risk assessment should include a site survey of the water system. A template is attached which is suitable for a basic system and can be adapted as required. The assessor should complete all the sections coloured blue.

The assessor should understand the water systems and any associated equipment in the property, in order to conclude whether the system is likely to create a risk from exposure to Legionella.

It is important to identify whether:

water is stored or re-circulated as part of the system (particular areas of risk include water tanks, dead legs, shower heads and/or long runs of pipe work containing warm water)

the water temperature in some or all parts of the system is between 20 – 45°C (hot water should be stored in any tanks at 60°C)

there are sources of nutrients such as rust, sludge, scale and organic matters

conditions are present to encourage bacteria to multiply

it is possible for water droplets to be produced and, if so, whether they could be dispersed, e.g. showers

there are parts of the system that are used infrequently e.g. guest bathrooms

it is likely that any of the tenants, residents, visitors etc are more susceptible to infection due to age, health or lifestyle and whether they could be exposed to any contaminated water droplets

Reviewing the risk assessment

If the risk assessment concludes there is no reasonably foreseeable risk or the risks are insignificant and are managed properly to comply with the law, the

assessment is complete. Although no further action may be required at this stage, existing controls must be maintained. The assessment of risk is an ongoing process and not merely a paper exercise. The assessment should be reviewed regularly and specifically when there is reason to suspect it is no longer valid.

Educating tenants

Landlords should inform tenants of the potential risk of exposure to Legionnaire’s disease within domestic properties and its consequences. They should advise on any actions arising from the findings of the risk assessment, where appropriate.

Tenants should be advised in particular that they should:

• inform the landlord/letting agent if they believe the hot water temperature is below 50°C or the hot water tank/boiler is defective in any way

• not adjust the temperature of the hot water

• advise landlord/letting agent if they believe the cold water temperature is above 20°C

• flush through little used outlets for 2 minutes at least once a week

• clean, disinfect and descale shower heads at least once every 6 months

• notify the landlord/letting agent if they notice any debris or discolouration in the hot or cold water

See & download

1. Legionella Check List

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