Legionella risk assessment for Farms and agricultural buildings

Updated 12 September 2026

A farm usually has two water systems side by side with different rules. The farmhouse is a domestic dwelling, managed like any home. The moment water is supplied to a workplace — the dairy, the staff canteen and toilets, the shower used after milking, the workshop washdown point — the Health and Safety at Work Act applies because people are at work there. Many farms are not on chlorinated mains water at all but on private supplies from boreholes or springs, which brings variable source quality, storage tanks and treatment equipment that all need to be part of the assessment rather than assumed safe.

Agricultural work generates aerosol routinely: parlour wash-down, pressure washers, hose reels and yard hydrants all turn water into spray in the breathing zone, so the quality of the supply feeding them matters in a way it does not in an office. Header tanks in the roof spaces of older farm buildings are common, often uninsulated and rarely inspected. Seasonal worker accommodation — static caravans and converted bothies — adds small self-contained systems that stand empty for months and need a documented recommissioning flush before each season.

The duty holder is the farm business, and the practical controls are familiar: hot water at 50°C at the staff welfare outlets, cold below 20°C, weekly flushing of anything little-used outside the main season, and an annual check of tanks and any treatment plant on the private supply. The assessment should record which parts of the system serve the workplace and which serve only the dwelling, because that boundary is where most farm water-safety arrangements quietly fall apart.

Is it legally required?

Farms employing anyone — including family members on the payroll and seasonal workers — are workplaces under the Health and Safety at Work Act 1974, and ACOP L8 and HSG274 apply to the water systems serving those workplaces. Private water supplies are separately regulated under the Private Water Supplies Regulations, which place duties on the relevant person for the supply and give the local authority monitoring and enforcement powers. Accommodation provided to seasonal workers is treated as part of the workplace arrangements for these purposes.

Who is the duty holder?

The duty holder is whoever has control of the premises or the water system. For farms and agricultural buildings 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:

1. 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
2. Produce a written scheme for preventing or controlling the risk, with specific tasks, temperatures, and frequencies
3. Implement, manage, and monitor the scheme in practice, not just on paper
4. Keep records of the assessment, the scheme, monitoring results, and any remedial action taken
5. Appoint a competent person (often called the "responsible person") to be accountable for the scheme

Specific water system risks to check

For farms and agricultural buildings 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 farms and agricultural buildings premises, that means at least every 24 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 farms and agricultural buildings premises typically costs between £200 and £600, 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.