Every legionella risk assessment under ACOP L8 starts with a schematic of the water system, because you cannot control what you have not mapped. This interactive diagram shows how the components of a typical system connect, and links each one to the routine check it needs under HSG274. Use it to learn the layout, then draw your own — your own schematic, with your own pipework, is the version that goes in your records.
Pick a component
Select a numbered hotspot on the diagram, or use the component key, to see what each part of the system does and the check it needs.
How to use this schematic
The diagram shows the journey water takes through a typical building: in from the mains, up the rising main, into storage, through the calorifier, and out to the taps. Legionella control is about keeping that journey hostile to bacterial growth — cold water cold, hot water hot, and no water standing still. Each numbered component is where that control either holds or fails.
Your own building will not match this drawing exactly. That is the point of the exercise: ACOP L8 expects a schematic of your system, kept up to date as pipework changes. Walk the building, trace the pipework, mark every tank, calorifier, TMV, dead leg and little-used outlet, and note the sentinel taps you will take temperatures from. This page is a worked example to copy from, not a substitute.
It records, it never certifies
A schematic is a record of what the system is and where the risks sit. Drawing one does not make a system safe or compliant — the control comes from doing the checks, at the right frequency, and writing down what you find. Keep schematics, temperature records and service records for at least five years.
Recording your system
The schematic is page one of a legionella risk assessment. Our free template gives you the rest of the structure — the risk rating, the control measures, the monitoring schedule — following ACOP L8 and HSG274 Part 2.