Free tool · Risk rating

Legionella risk-rating calculator

Answer a few questions for an indicative risk rating for your building. It helps you prioritise; it is not a competent risk assessment.

1. Who uses the building?

Healthcare, care home, or older/unwell/immunocompromised peopleMixed public (hotel, gym, school, leisure)Healthy adults at work (office, retail, light industrial)A private home, just the occupants

2. Which water systems are present? (tick all that apply)

Cooling tower or evaporative condenserSpa pool or hot tubShowers or spray tapsStored hot or cold water (tanks, calorifier, cylinder)Only mains-fed taps in daily use, nothing stored

3. Water temperatures?

Not measured / not sureSometimes lukewarm or out of rangeGenerally hot water hot (~50°C+) and cold cold (<20°C)

4. Any dead legs or little-used outlets where water can sit?

Yes, several little-used outlets or low-occupancy areasA fewNo

5. Is there a current risk assessment and monitoring in place?

No current assessment / monitoring, or unsureYes, documented and up to date

How to read the rating

This is an indicative score to help you prioritise, not a verdict. Lower means basic controls are usually enough; medium means an assessment and routine monitoring are expected; higher means a competent, site-specific assessment and active control should come first. Only a competent risk assessment can decide your real controls.

Indicative prioritisation aid based on HSE duties, not a risk assessment or legal advice. Source: HSE, what you must do; ACoP L8 (2013), “Carrying out a risk assessment”, p.12.

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"Legionella risk rating calculator (free)." Legionella.io. https://legionella.io/tools/legionella-risk-rating/

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