- cfu/l
- Colony forming units per litre, the unit used to report legionella sample results.
- Cooling tower
- A heat rejection unit that cools water by evaporation and can spread legionella in fine droplets if poorly managed.
- ACoP L8
- HSE's Approved Code of Practice for the control of legionella bacteria in water systems.
- Biofilm
- A slimy layer of micro-organisms on wet surfaces inside pipes and tanks that can shelter legionella.
- Calorifier
- A large hot water storage vessel heated by a primary circuit, common in commercial buildings.
- COSHH
- The Control of Substances Hazardous to Health Regulations 2002, which cover biological agents including legionella.
- Dead leg
- A length of pipe where water cannot flow, often left behind when an outlet is removed.
- Duty holder
- The employer or person in control of premises, legally responsible for controlling legionella risk.
- HSG274
- HSE technical guidance on legionella control, in three parts covering cooling systems, hot and cold water and other systems.
- Legionellosis
- The collective name for illnesses caused by legionella bacteria, including Legionnaires' disease.
- Pseudomonas aeruginosa
- A waterborne bacterium of particular concern in healthcare settings.
- Responsible person
- The person appointed by the duty holder to manage legionella control day to day.
- Sentinel outlet
- The outlets nearest and furthest from the hot water source or cold tank, used to monitor temperatures.
- TMV
- Thermostatic mixing valve, which blends hot and cold water to a safe temperature.
- TVC
- Total viable count, a general measure of bacteria in a water sample.
- Written scheme
- The document setting out how legionella risk in a system will be controlled and monitored.
Glossary
Water hygiene glossary
The key terms explained in plain English.