Legionella Risk Assessment
Assessment & Compliance Check in 24 HOURS
- All Prices are updated on October 12, 2026
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Do You Need a Legionella Risk Assessment?
Whether a legionella risk assessment is required depends on the type of premises, the design and maintenance of the water system, and who may be exposed to aerosolised water.
In the UK, dutyholders responsible for health and safety must consider legionella when managing workplace risks, including landlords, employers, facilities managers, and those in control of premises. A risk assessment is typically needed when there is a hot and cold water system that could support bacterial growth, water can stagnate, temperatures are poorly controlled, or vulnerable people may be present.
It helps determine whether existing controls are adequate, what monitoring is proportionate, and who should carry out key tasks. The assessment should be reviewed when there are changes to the building, occupancy, water use patterns, or the water system itself, and at suitable intervals. Clear records support ongoing management and demonstrate compliance with legal duties as well.
- Ensure Tenant Safety
- Comply with Health Regulations
- Prevent Costly Health Issues
- Increase Property Value
- Protect Your Reputation
- Efficient Risk Management
Which Water Systems Need a Legionella Risk Assessment?
In practice, which water systems need a legionella risk assessment comes down to one question: can they generate aerosol and provide conditions for bacteria to grow and spread? If the answer is yes, assessment is typically warranted, especially where people could inhale droplets or where vulnerable occupants are present in buildings.
Systems most often considered include hot and cold water services (tanks, heaters, calorifiers, long pipe runs, dead legs, and little-used outlets), showers and spray taps, spa pools and hot tubs, cooling towers and evaporative condensers, and decorative fountains or water features that atomise water.
Humidifiers, misting systems, certain industrial washers, and pressure washers used in enclosed areas can also create inhalable droplets. Any system with warm temperatures, stagnation, scale, sediment, biofilm, or inadequate disinfection increases concern. Temporary, seasonal, or modified installations deserve attention because control routines are often disrupted.
Hot & Cold Water Services
Showers & Spray Taps
Cooling Towers & Condensers
Fountains & Water Features
What Does a Legionella Risk Assessment Include (and Deliver)?
Because a compliant Legionella risk assessment is both a technical survey and a management review, it typically includes identifying all relevant water systems and their uses, mapping where aerosol may be generated, evaluating conditions that support bacterial growth (temperature control, stagnation, biofilm, scale, and nutrient sources), and checking existing control measures and responsibilities.
It then delivers a documented risk rating with clear, prioritised actions, monitoring and maintenance schedules, and evidence that risks are being controlled to the extent reasonably practicable.
In practice, the assessor gathers asset details, drawings, and operating information, verifies key components on site, and records how systems are managed day to day. The report usually includes a schematic of the water systems, an audit of written procedures, and identification of gaps in training, records, or contractor oversight.
Deliverables commonly include an action plan with timescales, roles, and recommended verification (for example, routine checks and review frequency), plus a summary suitable for dutyholders to sign off and implement promptly.
What Risks Are Assessors Checking For (Temperature, Stagnation, Scale)?
Assessors focus on the specific conditions that allow Legionella to multiply and spread via aerosol, then check whether those conditions are reliably controlled. They look for temperatures that sit in the growth band, especially in mixed systems where hot and cold services run close together or where return temperatures drift. They also examine stagnation: low-use outlets, oversized pipework, dead legs, and stored water that is not routinely turned over.
| Risk factor | What is checked | Why it matters |
| Temperature | Hot/cold distribution profiles | Growth window persists |
| Stagnation | Infrequent outlets, dead ends | Biofilm can develop |
| Scale | Limescale, sediment, corrosion | Surfaces protect bacteria |
| Aerosol | Showers, spray taps, and cooling | Inhalation exposure route |
Finally, they note evidence of scale and corrosion that can shelter bacteria and reduce disinfectant effectiveness, and they confirm whether aerosol-generating outlets are positioned and used in ways that increase exposure potential.
Who Is Qualified to Carry Out a Legionella Risk Assessment?
Who, then, is considered competent to carry out a Legionella risk assessment? Competence typically means practical experience with water systems, sound knowledge of Legionella control principles, and the ability to identify hazards, evaluate risk, and specify proportionate controls. The assessor should understand relevant UK guidance (including HSE L8 and HSG274) and be able to interpret system schematics, temperatures, usage patterns, and vulnerable populations.
Technical Knowledge
Hot/cold water and cooling systems, microbiology basics, control methods.
Practical Experience
Site surveys, plant room access, sampling awareness, and remedial prioritisation.
Regulatory Awareness
Duties of the responsible person include recording expectations and guidance standards.
Communication Skills
Clear reporting, actionable recommendations, limits and assumptions stated.
How Often Should You Review Your Legionella Risk Assessment?
Although a legionella risk assessment is not a one-off document, it should be reviewed at defined intervals and whenever a significant change could affect risk. Many organisations adopt an annual review as good practice, while higher-risk premises (such as care settings, hotels, or complex hot and cold water systems) may need more frequent checks.
A review confirms that control measures still match the system’s condition, use, and occupancy, and that monitoring records support the assessment’s assumptions. It also guarantees responsibilities, schematics, and written procedures remain accurate.
Reviews should be triggered when any of the following occurs:
- Alterations to pipework, tanks, calorifiers, showers, or water treatment equipment
- Changes in building use, occupancy levels, or vulnerable user groups
- Evidence of control failure, such as temperature excursions, poor biocide results, or positive samples
- Extended shutdowns, stagnation risk, or re-commissioning after refurbishment
Documenting review dates, findings, and resulting actions helps demonstrate ongoing compliance and reduces avoidable exposure to Legionella.
The Legionella Risk Assessment Process Explained
Landlord Safety Experts follows a thorough methodology to assess and manage Legionella risks, ensuring your property meets all health and safety standards.
Frequently Asked Questions
Legionella Risk Assessment Asked Questions
A legionella risk assessment typically costs £150–£500 for small domestic sites, and £500–£2,000+ for larger or complex premises. Pricing depends on property size, system complexity, travel, reporting scope, and accreditation.
A typical visit takes 1–3 hours, though simple sites may be under an hour and complex premises can take a full day. Duration depends on building size, water system complexity, access, and records.
Yes, an organisation can effectively fail if significant risks or legal non-compliance are found. Next, remedial actions are recommended, deadlines set, controls improved, and follow-up verification arranged; regulators or insurers may become involved if ignored.
Tenants or employees should usually be informed when findings affect their health or require behavioural changes. Communication is expected in the workplace and housing duties, explaining risks, controls, and actions. Minor issues without exposure may not require notification.
Records should include risk assessments, schematics, responsible person roles, control scheme details, monitoring logs (temperatures, flushing), sampling results, maintenance and disinfection certificates, training records, corrective actions, and review dates. Documentation should be dated, signed, and stored securely.
