Cooling tower legionella requirements in the UK: an owner's guide

Why cooling towers carry their own rules

A wet cooling tower or evaporative condenser sprays water through a stream of air to reject heat, and can release a fine mist. If legionella bacteria are growing in the water, that mist can carry them into the air. For that reason these devices have a specific notification regime and specific HSE guidance, separate from the general duty to manage water systems.

Duty one: tell the local authority

The Notification of Cooling Towers and Evaporative Condensers Regulations 1992 require the person in control of such a device to notify the local authority. Councils say this applies even where HSE is the enforcing authority, that it is free, and that you must also notify when the device is decommissioned or dismantled. Devices that hold no water exposed to air are outside the scope, so check the wording with your council if your equipment is unusual.

Duty two: assess and control the risk

The dutyholder must identify and assess the risk, have a written scheme for controlling it, and appoint a competent person to manage it. HSE's Approved Code of Practice L8, Legionnaires' disease: the control of legionella bacteria in water systems (fourth edition, 2013), sets out those duties. The technical detail for cooling systems is in HSG274 Part 1, covering evaporative cooling systems; its second edition was published in March 2024, with added information on test methodology and on how cooling water pH affects halogen biocides. Because the guidance is revised, use the current edition from HSE, not a copy a contractor supplied years ago.

What this means when you choose or replace plant

Water-cooled chillers served by a wet tower carry an ongoing monitoring, treatment and record-keeping obligation that air-cooled chillers and VRF systems do not. That does not make the tower the wrong choice, since it can be more efficient at large scale, but the lifetime cost should include the water treatment contract and the compliance workload. Our VRF vs chiller comparison and chiller guide cover the plant side, and planned preventive maintenance covers what a service contract should include.

This page is general guidance for building owners and is not legal advice. Your risk assessment must be done by a competent person for your site.

Sources and last checked

Checked on 18 October 2026. Regulations and guidance are revised, so confirm the current edition before you rely on it.

• HSE: L8 Legionnaires' disease, the control of legionella bacteria in water systems (4th edition, 2013)
• HSE: HSG274 Legionnaires' disease technical guidance (Part 1: evaporative cooling systems, 2nd edition, March 2024)
• Ipswich Borough Council: cooling towers and evaporative condensers notification
• Stockport Council: cooling towers and evaporative condensers