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UK Legionella standards & guidance

The documents that govern Legionella control in the UK, in plain English: what each one is, whether it binds you, what it covers, and a link to the official source. Start here when someone quotes a code at you and you need to know how much weight it actually carries.

ACoP L8 · Legionnaires' disease: the control of legionella bacteria in water systems

HSE · 4th edition (2013)
What it is
An Approved Code of Practice. It has special legal status: follow it and you are normally doing enough to comply; depart from it and, in a prosecution, you must show you achieved control another way.
Who it binds
Duty holders (employers and those in control of premises) under the Health and Safety at Work etc. Act and COSHH.
What it covers
The duties: identifying and assessing risk, appointing competent people, a written scheme of control, monitoring, records and review.
Full detailsOfficial sourceRead our explainer →

HSG274 · Legionnaires' disease: technical guidance

HSE · Second edition 2024 (Part 1 updated; Parts 2–3 carried over from 2014)
What it is
The detailed technical guidance that sits beneath L8: the practical "how", across three parts. It replaced the older, now-withdrawn HSG70.
Who it binds
Guidance (not an ACoP), but the recognised way to deliver the L8 duties.
What it covers
Part 1 cooling towers and evaporative condensers; Part 2 hot and cold water systems; Part 3 other risk systems. Temperatures, inspection intervals, cleaning and monitoring methods.
Full detailsOfficial sourceRead our explainer →

INDG458 · Legionnaires’ disease: a brief guide for dutyholders

HSE · Current edition (INDG458)
What it is
HSE’s free, plain-English leaflet summarising what a dutyholder must do to control Legionella - a sensible first read before the detail in L8 and HSG274.
Who it binds
Guidance for employers and those in control of premises; a summary of the duties, not a substitute for them.
What it covers
Identifying and assessing the risk, managing and controlling it, keeping records, and who is responsible.
Full detailsOfficial sourceRead our explainer →

ISO 11731 · Water quality. Enumeration of Legionella

ISO / BSI · ISO 11731:2017 (replaced ISO 11731:1998 and ISO 11731-2:2004)
What it is
The international standard laboratory culture method for isolating and counting Legionella in water samples - what an accredited lab follows to produce a CFU/L result.
Who it binds
A voluntary international standard (adopted in the UK as BS ISO 11731); the reference method behind your sample results.
What it covers
Sample concentration, culture on selective media, confirmation and enumeration of Legionella, reported as colony-forming units per litre (CFU/L).
Full detailsOfficial sourceRead our explainer →

BS 8580-2 · Water quality. Risk assessments for Pseudomonas aeruginosa and other waterborne pathogens. Code of practice

BSI · BS 8580-2:2022
What it is
The companion to BS 8580-1 covering risk assessment for Pseudomonas aeruginosa and other waterborne pathogens (e.g. non-tuberculous mycobacteria), especially in healthcare and other higher-risk settings.
Who it binds
A voluntary standard; the reference for assessing waterborne risks beyond Legionella.
What it covers
Hazards and hazardous events, assessor competence, site survey, risk rating and reporting for pathogens other than Legionella.
Full detailsOfficial source

Links go to the official publisher. Nothing here is legal advice; apply each document through a competent, site-specific risk assessment.

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