What Is HSG274?
- 2 days ago
- 5 min read
If you are responsible for managing a commercial building, you have almost certainly come across the term HSG274 at some point — probably in the context of legionella compliance or a water hygiene audit. But knowing what it is, what it actually requires, and how it fits into the wider legal framework is another matter. This guide sets out the essentials in plain language.
HSG274 Explained: The Basics
HSG274 is a series of technical guidance documents published by the Health and Safety Executive (HSE). The full title is Legionnaires' disease: Technical guidance, and it exists to explain in practical terms how duty holders should control the risk of Legionella bacteria in water systems.
The most important thing to understand about HSG274 is how it relates to ACoP L8 — the Approved Code of Practice that sits at the heart of the UK's legionella control framework. A useful way to think about the relationship between the two is this: ACoP L8 tells you what the law expects. HSG274 tells you how to actually do it.
ACoP L8 has special legal status. If you are prosecuted for a legionella-related breach and you have not followed ACoP L8, you will need to demonstrate that you have met the same standard by some other means. HSG274 does not carry that same legal weight — it is guidance rather than law — but it gives practical advice on meeting the legal requirements of the Health and Safety at Work etc Act 1974 and the Control of Substances Hazardous to Health Regulations 2002. In practice, following HSG274 is how most organisations demonstrate compliance.
Both documents are free to download from the HSE website, and between them they form the foundation of any defensible legionella management programme.
Who Does HSG274 Apply To?
HSG274 applies to duty holders — a term the guidance uses to describe employers, those in control of premises, and anyone with health and safety responsibilities for others. In a facilities management context, that almost certainly means you.
The five core duties HSG274 places on you are:
Identifying and assessing sources of risk in your water systems
Preparing a written scheme to prevent or control that risk
Implementing, managing, and monitoring the precautions set out in your scheme
Keeping records of those precautions
Appointing a Responsible Person to take day-to-day ownership
That last point is worth dwelling on. The Responsible Person role is often held by a facilities manager or estates lead. ACoP L8 is clear that whoever holds it must have adequate training, knowledge, skills, and experience to carry out the task — and the duty holder is responsible for satisfying themselves that this is the case.
The Three Parts of HSG274
HSG274 is divided into three parts, each covering a different category of water system. Understanding which parts are relevant to your site is important because it determines the scope of your compliance obligations. Part 1 was updated and republished in 2024 — the second edition of the guidance. Parts 2 and 3 remain as originally published in 2014
Part 1: Evaporative Cooling Systems
Part 1 covers cooling towers and evaporative condensers. These are the highest-risk systems for legionella because they generate fine water droplets — aerosols — that can travel considerable distances and be inhaled. If you operate a cooling tower, Part 1 is the section you need to know in detail, and you should also be aware that cooling towers must be notified to your local authority within one month of commissioning.
Part 2: Hot and Cold Water Systems
Part 2 is the section that applies to the greatest number of sites by far. It covers the hot and cold water systems found in virtually every commercial building — storage tanks, calorifiers, distribution pipework, showers, taps, and associated fittings. If your building has running water, Part 2 almost certainly applies to you.
This section sets out temperature targets (hot water stored at 60°C, cold water below 20°C at the outlet within two minutes), monitoring frequencies, inspection intervals, and guidance on specific higher-risk components such as thermostatic mixing valves, flexible hoses, and cold water storage tanks. It also includes guidance on flushing infrequently used outlets — something that is often overlooked but is a straightforward and effective control measure.
Part 3: Other Risk Systems
Part 3 addresses water systems that fall outside the first two categories — spa pools, hot tubs, humidifiers, decorative water features, and similar installations. If your building includes any of these, Part 3 sets out the relevant control requirements.
What HSG274 Means in Practice for Facilities Managers
Understanding the guidance is one thing. Translating it into day-to-day building management is where the real work lies.
The Written Scheme of Control
One of the core requirements of HSG274 is a written scheme — a documented plan that sets out your water systems, the risks associated with them, and the control measures you have in place. This document should reflect your actual building, not a generic template. It needs to be kept up to date and reviewed whenever there is a significant change to your systems, occupancy, or building use.
The Legionella Risk Assessment
The starting point for any HSG274-compliant programme is a legionella risk assessment. This is a systematic review of your water systems to identify where Legionella could proliferate and what controls are needed to prevent it. HSG274 requires it to be carried out by a competent person — typically a qualified water hygiene specialist — and it should be reviewed at least every two years, or sooner if there are changes to your systems.
If you are unsure what a risk assessment involves or what happens after one is completed, our article on what to do after a legionella risk assessment sets out the next steps clearly.
Monitoring and Record-Keeping
HSG274 is specific about monitoring requirements — temperature checks at sentinel points, microbiological sampling, and inspection of key components at defined intervals. All of this needs to be recorded. In the event of an HSE inspection or a legionella-related incident, your records are the primary evidence that your control programme was functioning. A gap in the paperwork is as much of a problem as a gap in the maintenance.
For a broader overview of what an ongoing water hygiene monitoring programme looks like in practice — including what should be checked, how often, and by whom — the water hygiene monitoring services section of this site is a useful reference.
The Consequences of Non-Compliance
HSG274 is guidance, but ignoring it carries real risk. If a legionella incident occurs at your premises and your arrangements cannot be demonstrated to meet the standard set by HSG274 and ACoP L8, you are exposed to HSE enforcement action, improvement or prohibition notices, and — in serious cases — criminal prosecution and unlimited fines. The reputational consequences can be equally damaging.
The practical takeaway is straightforward: HSG274 describes what a compliant, defensible water hygiene programme looks like. Building yours around it is the most reliable way to demonstrate that you have taken your duty of care seriously.
If you would like to understand more about your specific obligations and how a risk assessment maps to the requirements of HSG274, take a look at our legionella risk assessment services page — it covers what the process involves, who should carry it out, and what you should expect from the outcome.
