HSG274 vs ACOP L8 — what's the difference?
One is the code you must follow. The other is how to follow it.
ACOP L8 and HSG274 get used as if they were the same document. They are not, and the difference matters the moment you decide what to actually do.
One carries legal weight. The other tells you how.
ACOP L8 — the code with legal status
L8 is the Approved Code of Practice for controlling legionella bacteria in water systems. It has a special legal status: follow it and you are doing enough; depart from it and you have to show your alternative is at least as effective, or a court can treat the gap as evidence against you. The current edition gives that status to the risk assessment, the appointed responsible person, the written control scheme, and the review of those controls.
HSG274 — the technical how-to
HSG274 is the technical guidance that sits underneath L8. It is the detail: the temperatures, the intervals, what to monitor and how. It comes in three parts — Part 1 for evaporative cooling systems, Part 2 for hot and cold water systems, Part 3 for other risk systems. Most buildings live in Part 2.
How they fit together
L8 sets the duty: assess the risk, control it, monitor it, keep records. HSG274 puts numbers on it — for example, the monthly check that hot water reaches temperature at the outlet and cold stays below its limit. The code says you must monitor. The guidance says what monitoring looks like.
Where monitoring fits
Both assume someone is recording temperatures over time. Continuous sensors do exactly that, per outlet, against the HSG274 numbers — and the readings become the record L8 expects you to hold.
The point
L8 is what you are held to. HSG274 is how you meet it. Read together, they describe a regime that runs on temperature records over time — which is precisely what continuous monitoring produces.