Legionella in blocks of flats.
In short
Whoever controls a block's communal water system, such as tanks, a communal hot water supply or shared showers, must assess and control the risk from legionella under the Health and Safety at Work etc. Act 1974 and the COSHH Regulations 2002, following the HSE's Approved Code of Practice L8. The assessment must be reviewed regularly and whenever something changes; many agents review it every two years.
Does every block need a legionella risk assessment?
Any block with a communal water system that could let legionella grow needs one: stored water tanks, a communal hot water or heating system feeding outlets, or shared washing facilities. A block where every flat has its own mains-fed supply and nothing is shared may have little to assess, but that conclusion should itself be recorded.
How often should it be reviewed?
Regularly, and whenever there is reason to think it is no longer valid: a change to the system, a change in use, or a positive sample. There is no statutory interval; a two-year review is common practice for a stable residential system.
What controls the risk day to day?
Temperature, mainly. The HSE's guidance is to store hot water at 60°C or above and distribute it so it reaches at least 50°C at outlets, and keep cold water below 20°C. Little-used outlets should be flushed, and tanks inspected and kept clean. The assessment should say which checks apply to the building and how often.
Where Servanda comes in
Servanda keeps the assessment and its review date on the register, and turns each recommendation into a dated action so nothing in it is left for the next assessor to find again.
Everything Servanda doesThe law
The legislation is the authority; this page is a plain summary for England, checked on 2026-10-23. Wales and Scotland have their own rules. Take advice on any particular building.