Your Legal Obligation as a Landlord
If you rent out property in London — whether a single flat, an HMO, or a portfolio of residential units — you have a legal duty to assess and control legionella risk in the water system. This obligation comes from the Health and Safety at Work Act 1974, COSHH Regulations 2002, and the HSE's Approved Code of Practice L8 (ACOP L8).
This is not optional and applies regardless of property size or tenancy type. The HSE is clear: landlords are the 'duty holder' responsible for legionella risk management. You cannot delegate this responsibility to tenants, though you can appoint competent persons to carry out the technical work on your behalf.
What Gets Assessed
A competent assessor — typically a qualified water treatment engineer — surveys the entire water system. This isn't a quick visual check. A thorough assessment covers every component that stores, heats, cools, or distributes water in the property.
- •Water supply source and incoming mains arrangement
- •Cold water storage tanks — condition, lids, insulation, location
- •Hot water generation — boiler, calorifier, immersion heater settings
- •Distribution pipework — dead legs, unused branches, insulation
- •Outlet inventory — every tap, shower, bath, and appliance connection
- •Temperature measurements at sentinel and representative outlets
- •TMV (thermostatic mixing valve) locations and maintenance history
- •Water treatment equipment — dosing systems, filters, softeners
Typical Costs for London Properties
Risk assessment costs vary significantly based on property size and complexity. The table below gives typical price ranges for London properties. These are assessment costs only — any remedial work identified would be quoted separately.
| Property Type | Typical Cost | Assessment Time |
|---|---|---|
| Single flat / small rental | £100 – £200 | 1 – 2 hours |
| HMO (up to 6 rooms) | £150 – £300 | 2 – 3 hours |
| Small residential block (4–10 units) | £250 – £500 | Half day |
| Large residential block (10+ units) | £400 – £800+ | Full day |
| Commercial office / retail | £300 – £600+ | Half to full day |
| Hotel / care home | £500 – £1,500+ | 1 – 2 days |
How Often You Need One
The HSE recommends reviewing risk assessments at least every two years for most residential properties. However, a reassessment should also be triggered by specific events. The table below outlines when a new or updated assessment is needed.
| Trigger | Action Required |
|---|---|
| Every 2 years | Routine review of existing assessment |
| Change of building use | Full new assessment |
| Modification to water system | Assessment update or full reassessment |
| Extended vacancy (4+ weeks) | Pre-reoccupation check and flush |
| Tenant complaint about water quality | Investigation and possible reassessment |
| Positive legionella test | Immediate reassessment and remediation |
Consequences of Non-Compliance
The penalties for failing to manage legionella risks are severe. The HSE can issue improvement notices requiring immediate action. Criminal prosecution is possible in cases of serious neglect, with potentially unlimited fines. In the most serious cases — where negligence leads to illness or death — imprisonment is possible.
Beyond legal penalties, a legionella-related illness linked to your property would have devastating reputational consequences and expose you to civil compensation claims. The cost of a professional risk assessment is negligible compared to these risks.
Getting Started
Arranging your first legionella risk assessment is straightforward. A qualified water treatment specialist handles the entire process — from survey to report to implementing control measures. Most residential assessments can be completed in a single visit with minimal disruption to tenants. Between formal assessments, maintain ongoing controls: flush unused outlets weekly, check temperatures monthly, and keep records of everything.