Legionella Risk Assessment for Commercial Buildings: Costs, Risks & How to Book an Assessment

craigtawc
2 days ago
5 min read

Legionella Risk Assessment for Commercial Buildings: Costs, Risks, and How to Book an Assessment

Commercial buildings face increased and often complex challenges when it comes to managing water safety. Extensive pipework networks, variable occupancy levels, fluctuating water temperatures, ageing infrastructure, and changes in building use can all create conditions that allow Legionella bacteria to grow. For employers, landlords, and dutyholders, understanding and controlling these risks is not only a legal obligation but a fundamental responsibility for protecting health.

This guide explains why commercial buildings are at higher risk of Legionella, the most common issues found during inspections, what a commercial Legionella risk assessment includes, how much an assessment typically costs, and how to book a compliant service with confidence.

Why Commercial Buildings Face a Higher Risk of Legionella

Although Legionella bacteria can develop in any water system, commercial properties introduce additional layers of complexity. Larger systems are harder to monitor, and issues such as poor temperature control or low water usage can go unnoticed for long periods. Multi-storey buildings, extensions, refurbished areas, and older infrastructure all increase the likelihood of hidden risks.

During a Legionella risk assessment for commercial buildings, several recurring problems are commonly identified.

Common Legionella Risks in Commercial Water Systems

Poor Temperature Control Across the System

Legionella bacteria multiply most effectively at temperatures between 20°C and 45°C. Commercial water systems often struggle to maintain compliant temperatures due to long pipe runs, oversized calorifiers, undersized return loops, inadequate insulation, and irregular water use.

These issues can result in hot water failing to reach 60°C at the calorifier or 50°C at outlets, while cold water temperatures may rise above 20°C, particularly in older or poorly insulated buildings.

The solution:Effective control usually requires system balancing, insulation improvements, correct calorifier and thermostat settings, and regular temperature monitoring to confirm that corrective actions are working.

Dead Legs and Redundant Pipework

Changes to building layouts, tenant turnover, refurbishments, and system upgrades often leave behind capped pipes, unused outlets, or redundant pipework. These dead legs allow water to stagnate, creating ideal conditions for Legionella bacteria to grow.

The solution:A commercial Legionella risk assessment includes system mapping and the creation of schematic drawings and asset registers. These identify redundant sections of pipework so they can be removed or effectively managed through flushing where removal is not immediately possible.

Infrequently Used Outlets

In many commercial premises, certain areas are rarely used. Examples include showers in unused changing rooms, taps in vacant offices, or kitchens that operate seasonally. These outlets are among the most common sources of Legionella growth.

The solution:A documented flushing regime supported by accurate records is essential. In some cases, removing outlets that are no longer required provides a permanent reduction in risk.

Ageing Infrastructure and Poor Insulation

Many commercial buildings operate with outdated pipework, poorly insulated services, or pipework running through warm environments such as ceiling voids or plant rooms. These conditions can lead to heat gain in cold water systems and heat loss in hot water circulation systems.

The solution:Pipework insulation upgrades, replacement of degraded materials, and periodic inspections help maintain effective thermal control throughout the year.

Calorifier and Storage Tank Issues

Oversized calorifiers and cold-water storage tanks are common in commercial buildings, particularly where systems were designed for higher occupancy levels than currently exist. Oversizing increases water retention time, which raises the risk of bacterial growth.

Typical issues identified during a commercial Legionella risk assessment include sediment build-up, poor turnover, incorrect temperature settings, faulty thermostats, and limited access for inspection and maintenance.

The solution:Annual inspections, tank cleaning, improved turnover management, and, where appropriate, resizing or bypassing storage systems following professional evaluation.

Lack of a Written Scheme of Control and Poor Record-Keeping

Many commercial premises still operate without a clear Written Scheme of Control or consistent monitoring records. Without documentation such as temperature logs, flushing records, inspection reports, and evidence of staff training, a business cannot demonstrate legal compliance, even if the system appears to be functioning correctly.

The solution:A site-specific Written Scheme of Control that clearly defines responsibilities, monitoring frequencies, acceptable limits, and escalation procedures.

What Is Included in a Commercial Legionella Risk Assessment?

A professional commercial Legionella risk assessment is far more than a box-ticking exercise. It provides a clear, practical understanding of risk and how to manage it effectively.

A compliant assessment typically includes:

A full site walkthrough to identify all water systems, outlets, and usage patterns
Temperature monitoring at representative outlets, calorifiers, and storage tanks
Inspection of pipework condition, insulation, dead legs, and system materials
Evaluation of Legionella risk, including why the risk exists and how it can be controlled
A schematic drawing of the water system to support ongoing management
A detailed asset register listing all relevant water assets
Clear, prioritised recommendations based on risk level and legal guidance

The aim is to achieve compliance with HSE guidance such as ACOP L8 and HSG274, while making water safety practical and manageable for the site team.

Cost of a Commercial Legionella Risk Assessment

The cost of a commercial Legionella risk assessment varies depending on several factors. There is no fixed price, as every building and water system is different.

Typical cost considerations include the size of the building, the number of outlets, system complexity, the number of buildings on site, time required, and the level of reporting detail needed.

As a general guide, most commercial Legionella risk assessments range from £300 to £1,200, with larger or multi-site premises costing more.

While cost is important, the real value of a professional assessment lies in preventing enforcement action, avoiding system failures, reducing health risks, and protecting business continuity and reputation.

How to Book a Commercial Legionella Risk Assessment

Booking a commercial Legionella risk assessment is straightforward, but selecting a competent provider is essential. UK law requires assessments to be carried out by someone with suitable training, experience, and technical knowledge of water systems and HSE guidance.

A competent provider will be able to explain their methodology, qualifications, reporting standards, and ongoing support options.

What to Expect from a Commercial Legionella Assessment Quote

When requesting a quotation, it should clearly outline what is included. This typically covers time on site, the number of outlets assessed, whether schematic drawings and asset registers are included, reporting detail, travel arrangements, and report delivery timescales.

Transparent pricing ensures there are no unexpected costs and allows dutyholders to make informed decisions.

How Commercial Buildings Can Reduce Legionella Risk Immediately

Even before an assessment is carried out, there are practical steps commercial sites can take to reduce risk. These include maintaining hot water storage at 60°C, ensuring hot water return temperatures reach at least 50°C, keeping cold water below 20°C, flushing infrequently used outlets weekly, removing redundant pipework, improving insulation, and keeping accurate records.

Small actions can significantly reduce risk, particularly in large or ageing systems.

Final Thoughts: Legionella Compliance Is an Ongoing Process

A Legionella risk assessment for commercial buildings forms the foundation of water safety management, but it is not a one-off task. Water systems change over time as buildings are altered, occupancy levels shift, and usage patterns evolve.

Regular review, monitoring, and competent support are essential to maintaining compliance and protecting health.

If you need clarity on your legal duties, want to understand the cost of a commercial Legionella risk assessment, or are ready to book an assessment, professional support can make compliance clear and manageable.