How to Carry Out a Legionella Risk Assessment – Step-by-Step

A Legionella risk assessment is the first and most important step in protecting people from Legionnaires’ disease.

It identifies where bacteria could grow in your water system and sets out the control measures needed to prevent it.

In Doncaster, landlords, businesses, and duty holders are legally required to ensure their water systems are safe — and the risk assessment is how you prove it.

Why a Risk Assessment Is Needed

Legionella bacteria can multiply in water systems that are poorly maintained or where water temperatures encourage growth.

Hot water that is too cool, cold water that is too warm, and stagnant pipework are all common hazards.

A thorough risk assessment allows you to:

Identify hazards in your system
Decide who is at risk
Put effective control measures in place
Keep clear records for compliance inspections

Step-by-Step Process

Step 1 – Understand Your Water System
Begin with a clear diagram or description of all water sources, tanks, cylinders, outlets, and associated equipment. Include any rarely used outlets or “dead legs.”

Step 2 – Inspect and Test Temperatures
Measure hot and cold water temperatures at multiple points. Hot water should be stored at 60°C and reach at least 50°C at outlets within one minute. Cold water should be below 20°C.

Step 3 – Identify High-Risk Areas
Look for:

Stagnant water in unused pipework
Warm temperatures in cold water tanks
Limescale build-up
Areas where water droplets (aerosols) are produced

Step 4 – Assess Who Is at Risk
Consider whether building occupants include elderly residents, hospital patients, or others with weakened immune systems — these groups are more vulnerable to Legionnaires’ disease.

Step 5 – Document Control Measures
Examples include:

Adjusting thermostats to maintain safe water temperatures
Flushing rarely used outlets weekly
Cleaning and descaling shower heads
Removing redundant pipework

Step 6 – Create a Written Scheme of Control
This is your formal plan for keeping the system safe.

It should include maintenance schedules, responsibilities, and record-keeping methods.

Step 7 – Review Regularly
Risk assessments should be reviewed at least every two years, or sooner if:

The water system changes
Occupancy patterns change
There is a case of Legionnaires’ disease linked to the property

Doncaster-Specific Considerations

Properties in Doncaster range from historic terraced houses to modern industrial sites.

Older properties may have outdated plumbing that creates stagnation risks, while industrial sites can have large, complex systems requiring more rigorous testing.

Care homes, hospitality venues, and leisure facilities in Doncaster must take extra precautions due to the vulnerability of their occupants.

Why Use a Professional

While some landlords and small businesses may choose to carry out basic checks themselves, a qualified Legionella assessor can:

Spot hidden risks you may overlook
Use calibrated testing equipment
Provide documentation accepted by enforcement bodies
Advise on cost-effective remedial actions

Related Information

Arrange Your Legionella Risk Assessment in Doncaster

Call, text or WhatsApp or contact us online today to book your professional Legionella risk assessment and ensure your property is fully compliant with ACOP L8 and HSG274.

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