Scope: England, Wales and Scotland. The duty arises under health and safety law rather than housing law, so it does not diverge. Verified against HSE guidance on 10 August 2026.
This is the compliance item most often sold and least often understood. Both halves of the confusion cost landlords money: some pay for a document they do not need, and others conclude the whole thing is a scam and do nothing, which is worse.
The duty is real
Landlords have a duty under the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations to assess and control the risk of exposure to legionella bacteria in the water system. HSE's Approved Code of Practice L8 is the governing guidance.
It applies to essentially every let residential property with a water system. There is no small-landlord exemption.
The certificate is not
HSE states plainly that there is no requirement for a landlord to produce a "legionella certificate", and that assessments for most domestic rented properties do not require a specialist or a testing regime. Companies sell certificates anyway. Buying one is not unlawful and not useless — but it is not the duty, and holding one does not discharge the duty if no assessment was actually made.
What the law asks for is a risk assessment, recorded, and reviewed when something changes.
What a proportionate assessment looks like
For a typical house or flat with a combi boiler and no stored water, the risk is low and the assessment is short. What it should record:
- The system: combi, or stored hot water with a cylinder, or a cold water tank.
- Water temperatures — hot stored above 60°C, delivered above 50°C, cold below 20°C. Temperature is the main control.
- Dead legs — pipework to a removed appliance, an unused outlet, an old shower. These are the commonest real risk in a domestic property.
- Debris, scale or corrosion in the system.
- Any spray-generating outlet, especially showers.
- Whether any occupier is particularly vulnerable.
The two moments that matter most
- After a void. Water standing in a system at room temperature is exactly the condition legionella needs. Flush all outlets thoroughly before a new tenant arrives — this is the single most useful control there is, and it is free. See void periods.
- After work on the system. A replaced cylinder, a removed appliance leaving a dead leg, or a new shower all change the assessment.
Tell the tenant
Simple things do the work: run taps and showers for a few minutes after any period away, keep the shower head clean and descaled, do not turn the hot water thermostat down below 60°C to save money. Put it in the welcome pack alongside the day-one documents.
Run the free compliance check — legionella appears on the checklist with the duty explained, not a certificate demanded.
Common questions
Do landlords legally need a legionella certificate?
No. HSE states there is no requirement for a landlord to produce a legionella certificate, and that assessments for most domestic rented properties do not need a specialist or a testing regime. What the law requires is a recorded risk assessment, reviewed when something changes. Buying a certificate is not unlawful, but holding one does not discharge the duty if no assessment was actually made.
What does the assessment actually involve?
For a typical house or flat with a combi boiler the risk is low and the assessment is short. Record the system type, water temperatures — hot stored above 60°C, delivered above 50°C, cold below 20°C — any dead legs of pipework serving removed or unused outlets, debris or scale, spray-generating outlets such as showers, and whether any occupier is particularly vulnerable.
When is the risk highest?
After a void. Water standing at room temperature is exactly the condition legionella needs, so flushing every outlet thoroughly before a new tenant arrives is the single most useful control and it costs nothing. The other moment is after work on the system — a replaced cylinder, or a removed appliance leaving a dead leg.