Legionella Risk Assessment Checker
Answer 9 questions about your property's water system to assess legionella risk level and get specific recommendations.
1. What type of water heating does the property have?
Combi boilers heat water on demand with no storage — lowest legionella risk.
2. Does the property have a cold water storage tank (header tank)?
Common in older properties with a loft tank. Mains-fed properties (most combi setups) have none.
3. Is hot water stored at 60°C or above?
Check the cylinder thermostat. Legionella is killed at 60°C. Skip if combi boiler (no storage).
4. Does hot water reach 50°C at taps within one minute?
Run the hot tap for one minute and check with a thermometer. Water below 50°C at the tap is in the danger zone.
5. Is cold water below 20°C at taps?
Cold water above 20°C enters the legionella growth zone. Common if pipes run through warm spaces.
6. Are there any dead legs (capped-off pipes or removed outlets)?
Dead legs are sections of pipework no longer connected to an active tap or shower. Water stagnates in them.
7. Are there any taps or showers used less than once a week?
Spare bathrooms, utility room taps, or en-suites in unoccupied rooms. Stagnant water is a risk.
8. Are showerheads free of heavy limescale or visible biofilm?
Limescale and biofilm in showerheads can harbour legionella. Showerheads create aerosols — the main transmission route.
9. Has the property been empty for more than 7 days without flushing the water system?
Water sitting in pipes during void periods stagnates. All outlets should be flushed for 2 minutes before a new tenant moves in.
Legionella risk in rental properties
Legionella bacteria grow in stagnant water between 20–45°C. As a landlord, you have a legal duty under the Health and Safety at Work Act 1974 and COSHH regulations to assess and control legionella risk in your rental properties. The HSE recommends reviewing assessments every 2 years, after plumbing changes, and between tenancies. For most domestic properties with a combi boiler, the risk is low — but you still need a written record of your assessment.
Related guides
This tool is a guide only and does not constitute legal advice. Always verify requirements with current legislation at legislation.gov.uk. Last reviewed: February 2026.
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