WHY? Legionnaires’ disease is a potentially fatal form of pneumonia. It is normally contracted by inhaling tiny, airborne droplets containing viable legionella bacteria. Although everyone is susceptible to infection, with residents likely to be particularly vulnerable, water systems in care homes need particular consideration.
WHAT? Although legionella bacteria are widespread in natural water sources, outbreaks of the illness occur from exposure to legionella growing in purpose-built systems where water is maintained at a temperature high enough to encourage growth (between 20–45 °C) and where there are nutrients that support bacterial growth such as rust, sludge, scale, organic matter and biofilms. The bacteria are dormant below 20 °C and do not survive above 60 °C. It is important to keep your cold water as close to the incoming cold mains supply temperature as possible, and the hot water stored at least at 60°C and distributed so that it reaches a temperature of 50 °C (55 °C in healthcare premises) within one minute at the outlets.
HOW? Every dutyholder must take suitable precautions to prevent or control the risk of exposure to legionella by having:
- an up-to-date legionella risk assessment
- a written scheme of control in place,
- a schematic diagram of the hot and cold water system,
- records of all necessary checks, tests and inspections. Sample recording sheets (source HSE GB)
See HSG 274 part 2, ‘The Control of legionella bacteria in hot and cold water systems’; and HSE L8 of the ‘Approved Code of Practice for the control of legionella in water systems’.
The written scheme of control (WSOC) details who does what, and how; it needs to specify measures to take to ensure that risk assessment remains effective and should be laid out clearly in an easily accessible manner. This should include:
- inspection and chlorination of hot and cold water tanks annually or as per the risk assessment.
- annual servicing and cleaning of thermostatic mixing valves (TMVs).
- quarterly descaling and disinfection of shower head, hoses and taps.
- monthly temperature checks at the sentinel taps i.e. the flow and return temperatures at the calorifier, and outlets closest and furthest from the flow as well as a representative selection of points.
- the routine flushing of unoccupied rooms or infrequently used outlets.
The dutyholder must ensure that any recommendations listed in the Risk Assessment are carried out and signed off when completed; evidence of this may be requested during an inspection.