Legionella

Control Measures

The employer or person in control of the water system has a duty to put in place control measures that minimise the growth and spread of legionella.

If a water system presents a significant risk, the system owner must first consider if the risk can be eliminated. Where this is not possible is may be possible to substitute the system with a lower risk one.  The key point is to design, maintain and operate water systems that prevent or adequately control the growth and multiplication of legionella.

Detailed advice on controlling the risk from legionella can be found within Legionnaires' disease. The control of legionella bacteria in water systems. Approved Code of Practice and guidance (L8).

Where the risk cannot be prevented, the Approved Code of Practice (ACOP) outlines the need for a written control scheme that clearly outlines effective control measures.

A simple guide entitled Legionnaires’ disease, a brief guide for dutyholders provides information on preventing or controlling the risks from legionella. The general principles are as follows:

• Ensure that the release of water spray is properly controlled.
• Avoid water temperatures and conditions that favour the growth of legionella and other micro-organisms.
• Ensure water cannot stagnate anywhere in the system by keeping pipe lengths as short as possible or by removing redundant pipework.
• Avoid fittings and materials that encourage the growth of legionella.
• Keep the system and the water in it clean.
• Treat water to either kill legionella (and other microorganisms) or limit their ability to grow.

To ensure control measures remain effective, the condition and performance of the system must be monitored which may be as simple as checking any control measures are working properly to inspecting the water system for any damage or contamination.

More detailed guidance relating to the control of legionella in water systems is contained within Legionnaires’ disease: Technical Guidance. The technical guidance, also referred to as HSG274, is in three parts, detailing control measures in various types of water systems (evaporative cooling systems, hot and cold water systems and other risk systems).