Guide
L8 and HSG274 explained for facilities managers
L8 and HSG274 are the two HSE documents behind every legionella risk assessment. You do not need to read them cover to cover. You do need to know what they ask of you.
By the Germ3 Water team. Updated 20 October 2026.
L8: the Approved Code of Practice
L8 is HSE's Approved Code of Practice on controlling legionella in water systems. The current version is the fourth edition from 2013.
An Approved Code of Practice has a special legal status. If you are prosecuted and did not follow it you must show you met the law in some other way that was just as good. In practice most duty holders follow L8.
What L8 asks you to do
- Identify and assess the sources of legionella risk.
- Prepare a written scheme to prevent or control the risk.
- Put the scheme in place and manage it.
- Keep records of the checks and the work done.
- Appoint a responsible person to manage it day to day.
HSG274: the technical guidance
HSG274 is the technical detail that sits under L8. It comes in three parts:
| Part | Covers |
|---|---|
| Part 1 | Evaporative cooling systems such as cooling towers. |
| Part 2 | Hot and cold water systems. This is the part most buildings need. |
| Part 3 | Other risk systems such as humidifiers and some industrial equipment. |
Spa pools have their own HSE guidance in HSG282.
The temperatures that matter
For most hot and cold water systems temperature is the main control. HSG274 Part 2 sets these targets:
| Where | Target |
|---|---|
| Hot water stored in a calorifier | At least 60°C |
| Hot water at outlets | At least 50°C within one minute. At least 55°C in healthcare. |
| Cold water at outlets | Below 20°C within two minutes |
The routine checks in HSG274 Part 2
- Monthly temperature checks at sentinel outlets.
- Monthly checks of calorifier flow and return temperatures.
- Weekly flushing of outlets that are used less than once a week.
- Annual inspection of cold water storage tanks.
- Cleaning and descaling of showerheads and hoses every three months or as needed.
- Servicing of TMVs as the manufacturer and your assessment require.
Your written scheme should turn these into a timetable for your building. It should say who does each one.
Cooling towers must be notified
If your site has a cooling tower or evaporative condenser you must notify your local authority. This is required by the Notification of Cooling Towers and Evaporative Condensers Regulations 1992.
Questions
Common questions
Is L8 the law?
L8 is an Approved Code of Practice. It is not law in itself but it has special legal status. If you do not follow it you must show you met the law another way.
Which part of HSG274 applies to my building?
For most offices and shops and hotels it is Part 2 on hot and cold water systems. Cooling towers fall under Part 1.
What temperature should hot water be for legionella control?
Stored hot water should be at least 60°C. Outlets should reach at least 50°C within one minute or 55°C in healthcare buildings.
Find out what your building actually needs
Book a survey and we will give you a fixed quote. You will also get an honest view of what you can safely do in house.
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