Legionella Risk Assessments Explained

For organisations and those responsible for managing buildings, understanding Legionella risk assessments is an essential part of wider building compliance and health and safety management. In this blog we explore what Legionella is and why it's imperative that organisations manage the risks associated with it.

As part of Ventro’s new Water Compliance division, we support organisations across the UK with practical, risk focused Legionella compliance services designed to help clients maintain safe, compliant, and resilient water systems. 

Understanding Legionella and the Risks it Presents

Legionella bacteria naturally exists within water sources such as rivers and lakes, but problems occur when the bacteria is allowed to grow within man-made water systems. Conditions such as stagnant water, poor circulation, incorrect water temperatures, or infrequently used outlets can all contribute to bacterial growth.

The greatest risk occurs when contaminated water droplets become airborne and are inhaled. This can happen through common building systems including showers, taps, cooling systems, storage tanks, spa pools, and certain air conditioning systems.

While anyone can be affected, some groups are considered more vulnerable than others. Older people, individuals with respiratory conditions, smokers, and those with weakened immune systems are generally at greater risk of developing serious illness following exposure.

Because of this, effective water management is not simply a maintenance issue. It is a critical health and safety responsibility that can directly affect building occupants, residents, patients, staff, and visitors.

Why Legionella Risk Assessments Matter

Legionella risk assessments form the foundation of effective water safety management. They are intended to identify where risk exists within a building’s water systems and determine what measures are needed to control that risk.

In the UK, organisations have legal responsibilities under legislation and guidance including the Health and Safety at Work etc. Act 1974, COSHH Regulations, ACOP L8, and HSG274 guidance. These duties apply across a wide range of sectors and place responsibility on duty holders to ensure water systems are properly assessed and managed.

Importantly, a Legionella risk assessment should never be viewed as a standalone compliance document produced purely to satisfy legislation. When approached properly, the assessment becomes a practical tool that helps organisations better understand their buildings, identify weaknesses within water systems, and implement more proactive maintenance and monitoring strategies.

Without appropriate assessment and ongoing management, organisations may expose themselves to enforcement action, financial penalties, reputational damage, and most importantly increased health risks for building occupants.

Which Buildings Require Legionella Risk Assessments?

Legionella responsibilities apply across a wide variety of building types and sectors. Social housing providers, healthcare organisations, schools, commercial offices, industrial facilities, retail environments, hospitality settings, and public sector estates may all require Legionella risk assessments depending on the nature of their water systems.

Responsibility often sits with landlords, facilities managers, managing agents, or Responsible Persons overseeing building safety and compliance. In many cases, organisations are managing large and complex estates with ageing infrastructure, varying occupancy levels, and changing building usage patterns, all of which can influence Legionella risk.

As buildings become more operationally complex, maintaining visibility across water systems and compliance requirements becomes increasingly important.

What Happens During a Legionella Risk Assessment?

A Legionella risk assessment involves a detailed review of a building’s water systems, associated assets, and existing control measures. The aim is to identify where conditions may allow Legionella bacteria to develop and determine whether current management arrangements are sufficient in mitigating the risk.

During the assessment, water systems are inspected to understand how they operate, how water is stored and distributed, and whether any areas present elevated risk. This often includes reviewing water temperatures, identifying stagnation risks, inspecting storage tanks and outlets, assessing system condition, and reviewing maintenance records and monitoring procedures.

Assessors will also consider factors such as vulnerable occupants, infrequently used outlets, dead legs within pipework, and the overall suitability of existing control measures.

The outcome is a detailed report outlining identified risks alongside recommendations designed to improve safety, strengthen compliance, and support ongoing water management.

Common Issues Identified in Water Systems

Many Legionella related issues stem from relatively common problems within building water systems. Poor temperature control, oversized storage systems, underused outlets, and redundant pipework can all contribute to increased risk if not properly managed.

In some buildings, maintenance regimes may not align with the complexity or usage of the system. In others, records may be incomplete or historic changes to infrastructure may no longer be accurately reflected within schematics and documentation.

One of the key benefits of a Legionella risk assessment is the ability to identify these issues before they develop into more significant compliance or health concerns. Early intervention allows organisations to take a more proactive and manageable approach to water safety.

Legionella Compliance Requires Ongoing Management

Completing a Legionella risk assessment is only one part of effective water compliance. Long term compliance relies on ongoing monitoring, maintenance, and review to ensure systems continue operating safely over time.

This may involve temperature monitoring, flushing regimes, tank inspections, chlorination works, planned preventative maintenance, and regular review of written schemes of control. Accurate record keeping also plays an essential role in demonstrating and evidencing that risks are being actively managed.

Importantly, Legionella risk assessments should also be reviewed whenever significant changes occur within a building or water system. Changes in occupancy, alterations to infrastructure, low usage areas, or system upgrades can all affect risk levels and may require reassessment.

For many organisations, maintaining this level of oversight across large property portfolios can be challenging without structured support and clear compliance processes.

Water Compliance as Part of a Wider Building Compliance Strategy

Water compliance does not operate in isolation. It sits alongside wider building safety responsibilities including fire safety, electrical compliance, air quality management, and ongoing building maintenance.

As part of the wider Ventro Group, our Water Compliance division forms part of an integrated building compliance approach spanning Fire, Electrical, Security, Air, and Water services. This joined up model enables organisations to work with a single compliance partner capable of supporting multiple compliance disciplines across the full building lifecycle.

By taking a more integrated approach, organisations can simplify contractor management, improve visibility across compliance activities, and create more consistent approaches to risk management, reporting, and long-term asset planning.

Why Organisations Choose Ventro

Ventro’s Water Compliance division provides nationwide support for organisations looking to strengthen their approach to Legionella management and wider water compliance.

Our services cover the full compliance lifecycle, from Legionella risk assessments and written schemes of control through to water monitoring, chlorination works, remediation projects, and planned preventative maintenance. Every service is delivered in alignment with ACOP L8 and HSG274 guidance, helping clients maintain safe and legally compliant environments.

What sets Ventro apart is our ability to combine technical expertise with wider integrated compliance capability. By operating across multiple building compliance disciplines, we help organisations take a more joined up approach to safety, risk management, and operational resilience.

Ventro’s View

Legionella compliance is often viewed as a standalone requirement, but in reality it forms part of a much wider building safety and risk management strategy. As buildings become more complex and compliance expectations continue to evolve, organisations are under increasing pressure to demonstrate that risks are being actively identified, managed or mitigated, and reviewed.

At Ventro, we believe effective water compliance relies on a structured, ongoing approach supported by clear visibility across assets, consistent monitoring, and integrated compliance management. By combining Water, Fire, Electrical, Security, and Air compliance services under one roof, we help organisations take a more joined up approach to building safety, creating safer environments while simplifying compliance management across the wider estate.

Speak to Ventro

If you would like to discuss Legionella risk assessments or wider water compliance support, speak to Ventro’s Water Compliance team today to find out how we can help support your organisation.