Control Of Legionella Bacteria In Water Systems Guidance

The HSE has recently updated their guidance on the management and control of Legionella bacteria in water systems. The Third Edition of the ACOP L8 was written in 2000 and the technical guidance was out of date.

The Fourth Edition has now been published without this guidance and includes some changes designed to simplify and clarify requirements.


Revised technical guidance is published separately online in a new Health & Safety Guidance document named HSG274 “Legionnaires’ disease: Technical guidance” and comes in three parts:


Part 1 – The control of Legionella bacteria in evaporative cooling systems

Part 2 – The control of Legionella bacteria in hot and cold water systems – interim guidance

Part 3 – The control of Legionella bacteria in other risk systems


The guidance is intended for duty holders to help them comply with their legal duties, which include undertaking risk assessments, appointing a person to be managerially responsible, preparing and implementing a scheme to prevent or control risk, managing and monitoring the scheme and keeping records. It gives practical advice on the legal requirements of the Health & Safety at Work Etc. Act, 1974, the Control of Substances Hazardous to Health Regulations 2002 concerning the risk from Legionella bacteria and guidance on compliance with the relevant parts of the Management of Health & Safety at Work Regulations 1999.


Part 1 contains the most significant changes – there is more detailed guidance on the records that should be kept and the biological, physical and chemical conditions that are considered acceptable and those which are not. Furthermore, there is an increased focus on ensuring that those responsible for evaporative cooling systems take an active role in the operation and management of the equipment.


Part 2 is not significantly different to the guidance contained in the Third Edition of the ACOP L8, however, Part 2 is scheduled for further revisions in 2014.


Part 3 provides guidance on a number of less common or specialised water applications that are known to be potential sources of Legionella infections. More systems are covered in more detail however, the document is clear that each system must be assessed on the basis of individual circumstances and an appropriate scheme of precautions devised by a competent person. The guidance acknowledges that in some cases it may be necessary to combine the knowledge of more than one individual in order to complete the risk assessment.


The new ACOP & guidance can be obtained as a free downloads from the HSE website:


HSG274 –