Legionella risk assessment for Factories and industrial premises
Updated 16 August 2026
Key points
- A legionella risk assessment is required for factories and industrial premises premises under the Health and Safety at Work Act 1974 and the Approved Code of Practice L8
- Typical cost: £400 to £2500
- Review every 12 months, or sooner if the water system, its use, or the people using it change
- A named duty holder (usually the employer, landlord, or building operator) must arrange it and act on its findings
Industrial water systems are usually the most complex any single building operator encounters. Process cooling, evaporative cooling towers, humidification systems, quench tanks, and industrial washers all generate aerosols and routinely operate at temperatures that favour legionella growth. A single cooling tower can carry aerosolised water hundreds of metres downwind, and HSE investigation reports document community cases linked to industrial towers identified well beyond the factory boundary.
Cooling towers and evaporative condensers are notifiable to the local authority under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992. The written scheme for a tower normally requires quarterly water sampling to a UKAS-accredited laboratory, continuous biocide dosing, and a documented clean and disinfection every six months. Any positive legionella count above 1,000 cfu/litre requires immediate action and an investigation.
In addition to the cooling system, factories often have canteen kitchens, staff showers, welfare blocks, and sometimes accommodation, each needing its own controls. The scale of the duty typically means a formal water safety plan, a named responsible person at senior management level, and a specialist water hygiene contractor.
Is it legally required?
Industrial premises are commercial premises under the Health and Safety at Work Act 1974 and ACOP L8. The Notification of Cooling Towers and Evaporative Condensers Regulations 1992 apply to any wet cooling tower or evaporative condenser, requiring notification to the local authority. HSG274 Part 1 gives specific technical guidance on cooling tower systems, and is the standard reference for industrial water hygiene.
Who is the duty holder?
The duty holder is whoever has control of the premises or the water system. For factories and industrial premises premises, this is usually the employer, owner, landlord, or managing agent. The duty cannot be contracted out: you can hire a water hygiene consultant, but the legal responsibility still sits with you.
If you are unsure who holds the duty for your premises, see: Who is responsible for a legionella risk assessment?
What the assessment should cover
ACOP L8 sets out five things a suitable and sufficient assessment must do:
- Identify and assess sources of risk across the whole water system, including stored hot and cold water, dead legs, rarely used outlets, and any equipment that generates aerosols
- Produce a written scheme for preventing or controlling the risk, with specific tasks, temperatures, and frequencies
- Implement, manage, and monitor the scheme in practice, not just on paper
- Keep records of the assessment, the scheme, monitoring results, and any remedial action taken
- Appoint a competent person (often called the "responsible person") to be accountable for the scheme
Free legionella risk assessment template
A structured Word document following the five-step approach in ACOP L8. Covers risk identification, written scheme, monitoring, and records. If it isn't written down, you can't evidence it.
Follows ACoP L8 and HSG274 Part 2. Free. No spam.
Specific water system risks to check
For factories and industrial premises premises, assessors typically pay close attention to:
- Hot water storage temperatures (calorifiers must reach 60°C throughout)
- Hot water distribution temperatures (50°C within one minute at outlets)
- Cold water storage tank condition, lid seal, and temperature (below 20°C)
- Dead legs, redundant pipework, and little-used outlets
- Shower heads, flexible hoses, and thermostatic mixing valves
- Any cooling tower, evaporative condenser, or spa pool (these are notifiable to the local authority under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992)
How often to review
There is no fixed legal interval, but ACOP L8 requires that the assessment is reviewed regularly and whenever there is reason to believe it may no longer be valid. For most factories and industrial premises premises, that means at least every 12 months and sooner after any of the following:
- Changes to the water system (new pipework, fittings, equipment)
- Changes to the use of the building or the number of occupants
- A positive legionella test result or a case of Legionnaires' disease linked to the premises
- Prolonged periods of low occupancy or system shutdown (a risk during holidays, term breaks, or refurbishment)
- New guidance from HSE
Typical cost
A professional legionella risk assessment for factories and industrial premises premises typically costs between £400 and £2500, depending on the size of the building, the number of water outlets, and whether there are any cooling towers or evaporative condensers (these add significantly to the cost because of the statutory inspection regime).
Use our cost calculator for an estimate based on your specific water system.
Need a legionella risk assessment for your premises? We will be partnering with Legionella Control Association registered providers shortly.
Free legionella risk assessment template
A structured Word document following the five-step approach in ACOP L8. Covers risk identification, written scheme, monitoring, and records. If it isn't written down, you can't evidence it.
Follows ACoP L8 and HSG274 Part 2. Free. No spam.