Published 2 August 2026 by Prop-Pocket Team
Learn how to conduct a legionella risk assessment for your rental properties. Follow our checklist to ensure compliance and keep tenants safe.
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Yes, you must carry out a legionella risk assessment for every rental property you own or manage. This is a legal duty under the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations (COSHH). The HSE is clear: the duty is to assess and control the risk, not to obtain a formal certificate. For most standard domestic properties, a simple, proportionate assessment is all that is required.
Three things to do right now:
The HSE's guidance makes one point worth holding onto: domestic water systems are often low risk because of regular water turnover. Proportionate action, properly recorded, is what the law expects.
The legal framework sits across two pieces of legislation. The Health and Safety at Work etc. Act 1974 places a general duty on anyone in control of premises to manage risks to health. COSHH specifically covers biological agents, which includes Legionella bacteria. Together, they require you to identify whether a risk exists, assess its level, put controls in place, and keep a record.
The HSE's Approved Code of Practice L8 and the technical guidance HSG274 Part 2 set out what a proper assessment should include: a description of the water system, an evaluation of risk, operating procedures, monitoring arrangements, and clear allocation of responsibility for ongoing checks.
Key legal points to understand:
The standard you are measured against is competence and proportionality, not perfection.
Every landlord is a dutyholder under COSHH, including those with a single rental property. There is no minimum portfolio size that triggers the duty, and no exemption for furnished holiday lets or HMOs that are already licensed under separate schemes.
The water systems that need assessing in residential properties include:
A modern property with a combi boiler and no stored water is genuinely lower risk. Water is heated on demand and not stored, so there is little opportunity for bacterial growth. You still need to assess it, but the assessment will typically be brief and the risk rating low. A Victorian terrace with a loft tank and an immersion heater, or an HMO with a shared hot-water cylinder, requires more careful evaluation.
The HSE's guidance for dutyholders frames the process in three stages: identify the hazard, assess the level of risk, and decide on control measures. Here is how that translates into a practical on-site checklist.
Landlord inspecting kitchen tap with checklist
Step 1: Confirm the system type
Establish whether the property has a combi boiler (no stored water) or a stored hot-water system. Note the presence of any cold-water header tanks, calorifiers, or secondary circulation loops.
Infographic of legionella risk assessment steps
Step 2: Walk the system
Inspect all water outlets: kitchen taps, bathroom taps, showers, outside taps, and any garden hose connections. Note any outlets that are rarely used or have been capped off.
Step 3: Check for dead legs
Dead legs are sections of pipework that no longer connect to an active outlet. Water stagnates in them. If you find any, they should be removed or flushed regularly.
Step 4: Inspect tanks and cylinders
Check cold-water header tanks for debris, insulation, and a fitted lid. Check the hot-water cylinder thermostat setting. The target is 60°C storage temperature.
Step 5: Check showerheads
Remove and inspect showerheads for scale and biofilm. Note whether flexible hoses are in good condition or show signs of deterioration.
Step 6: Temperature check
Run the hot tap at the furthest outlet from the boiler or cylinder. It should reach 50°C within one minute. Cold water at the tap should be below 20°C.
Step 7: Rate the risk and record your findings
| Risk rating | Triggers | Immediate action |
|---|---|---|
| Low | Combi boiler, no stored water, all outlets in regular use | Record assessment, review at next tenancy change |
| Medium | Stored hot water, occasional dead legs, showerheads with scale | Implement temperature controls, flush infrequently used outlets monthly, clean showerheads |
| High | Cold-water tank with debris, thermostat below 60°C, long void period, large HMO communal system | Immediate remedial action, consider professional assessment, thermal flush before re-letting |
Step 8: Complete your record
Your written record should capture: property address, assessor name and competence basis, date of assessment, system type and description, findings from each step above, risk rating, corrective actions required and by whom, and the next review date.
Storing this digitally, linked to the property record and the tenancy file, means you can retrieve it quickly if asked. A landlord inspection guide can help you combine this with other scheduled safety checks to save visits.
Pro Tip: Combine your legionella assessment with the annual gas safety check visit. Both require access to the property, and bundling them reduces disruption for tenants and cuts your admin time significantly.
Temperature is the primary control for Legionella in domestic water systems. The bacteria multiply most rapidly between 20°C and 45°C. Keep water outside that range and you remove the conditions for growth.
| Control measure | Target | Frequency |
|---|---|---|
| Hot-water storage temperature | 60°C at the cylinder | Check thermostat setting at each assessment |
| Hot-water outlet temperature | 50°C within 60 seconds | Check at furthest outlet during assessment |
| Cold-water temperature at outlet | Below 20°C | Check during assessment, especially in summer |
| Flushing infrequently used outlets | Run for 2–3 minutes | Monthly, or before each new tenancy |
| Showerhead cleaning and descaling | Remove scale and biofilm | Every three to six months |
| Thermostatic mixing valve (TMV) servicing | Maintain to manufacturer's schedule | Annually or per manufacturer guidance |
RentSmart Wales guidance lists flushing, temperature controls, and showerhead cleaning as the core practical controls for landlords, and that aligns with HSE expectations.
On microbiological testing: the HSE states that testing or sampling is not usually required for domestic hot and cold water systems. Temperature monitoring is a more reliable and proportionate control check. Testing may be justified where a case of Legionnaires' disease has been linked to the property, where a risk assessment identifies specific concerns, or where a large communal system in an HMO warrants verification. For a standard two-bedroom rental with a combi boiler, routine microbiological testing is not expected.
Additional maintenance checks worth scheduling:
Good record-keeping is the practical difference between a landlord who can demonstrate compliance and one who cannot. The fields your record should include:
Store records digitally where possible, linked to the property and the tenancy. This makes retrieval straightforward if a tenant raises a concern, an inspector requests evidence, or you need to brief a new managing agent. Retention for the duration of the tenancy plus a reasonable period afterwards is sensible practice; many landlords align this with their general tenancy document retention.
Review triggers to act on immediately include change of tenancy, system changes, long void periods, and evidence that controls are failing. The HSE recommends reviewing the assessment at least every two years, or sooner when any of these triggers apply. Many letting agents review at every change of tenancy as a matter of routine, which is a sensible approach for an active portfolio.
The HSE is explicit: you may be competent to carry out the assessment yourself. Competence means having sufficient training, experience, and understanding of the system to assess it accurately. For a straightforward domestic property, many landlords meet that bar.
When a DIY assessment is appropriate:
When to hire a competent external assessor:
If you appoint a contractor, ask them:
For a standard domestic property, a professional assessment typically takes one to two hours on site. Costs vary by property size and system complexity; larger HMOs with stored water attract higher fees than a simple single-let. Getting two or three quotes is straightforward and worthwhile for anything beyond a basic combi-boiler property.
Void periods are the highest-risk scenario in a rental portfolio. When a property sits empty, water temperature in the pipes drifts into the 20–45°C danger zone, and stagnation allows any bacteria present to multiply. The risk is well documented: void periods are the moment when Legionella becomes a real problem in rental properties.
For properties empty for less than a month:
For properties empty for more than a month, a thermal flush is required:
Pre-letting commands before a new tenancy begins:
If you manage multiple properties, building void flushing into your re-letting checklist removes the risk of it being overlooked under time pressure.
Enforcement sits with the HSE and, in some cases, local authorities. Under the Health and Safety at Work etc. Act and COSHH, inspectors have powers to issue improvement notices, prohibition notices, and, in serious cases, to prosecute. A prosecution can result in an unlimited fine for a company or an organisation, and a custodial sentence for an individual in the most serious cases.
Civil liability is a separate exposure. If a tenant contracts Legionnaires' disease and you cannot demonstrate that you assessed and controlled the risk, a civil claim for damages becomes significantly harder to defend. Your written records are the primary line of defence.
Practical steps if a problem arises:
The practical reality is that most enforcement action follows from a failure to have any records at all, not from a minor technical shortcoming in an otherwise well-managed system.
Keeping legionella records alongside gas safety certificates, EICRs, and PAT test records in separate folders or spreadsheets creates gaps. Prop-pocket centralises all compliance documentation in one place, so nothing gets missed when a tenancy changes or a review date passes.
Practical ways Prop-pocket supports your legionella risk management plan:
A quick example: when a tenancy ends, Prop-pocket can trigger a reminder to carry out a void flush and review the legionella assessment before the next let begins. That reminder sits alongside the gas safety renewal prompt, so both are handled in the same visit.
Pro Tip: Use Prop-pocket's document storage to keep a copy of the original HSE guidance alongside your assessment record. If you are ever asked to demonstrate your competence basis, having the reference material attached to the record is a straightforward way to show your working.
All compliance data stored in Prop-pocket is held securely, with access controls that let you share specific records with contractors or managing agents without exposing your full portfolio data.
UK landlords must carry out a legionella risk assessment under COSHH and the Health and Safety at Work etc. Act, keep a written record of findings and controls, and review the assessment at least every two years or sooner if there is a change of tenancy, system changes, or reasons to believe the assessment is no longer valid.
| Point | Details |
|---|---|
| Legal duty applies to all landlords | Every landlord, including single-property owners, must assess and control legionella risk under COSHH. |
| No certificate required | The law requires a documented assessment and controls, not a formal legionella certificate. |
| Void periods are highest risk | Flush all outlets and carry out a thermal flush for properties empty more than a month before re-letting. |
| Review assessment at least every two years or sooner | Review triggers include change of tenancy, system alteration, void period, or evidence controls are failing. |
| Prop-pocket centralises compliance | Store assessments, set review reminders, and export records from one dashboard alongside other statutory checks. |
Most domestic rental properties are genuinely low risk when managed sensibly. A combi boiler, regular occupancy, and a thermostat set correctly means the conditions for Legionella growth rarely develop. The HSE's own guidance says as much. The problem is not the risk itself; it is the paperwork gap that leaves landlords exposed when something does go wrong.
The three mistakes that come up repeatedly are worth naming directly. First, confusing microbiological testing with temperature monitoring. Testing is not routinely required for domestic systems, and paying for it annually on a standard single-let is unnecessary. Temperature checks and flushing are the controls that matter. Second, forgetting void flushing. It is the highest-risk moment in the tenancy cycle and the one most often skipped under time pressure between lets. Third, assuming a certificate is required. There is no legionella certificate in UK law. A landlord who has a well-documented assessment and a record of temperature checks is in a stronger position than one who has paid for an annual test but has no written assessment on file.
The practical answer is proportionate action, properly recorded. A simple assessment for a combi-boiler property takes less than an hour. Combining it with a gas safety visit means no extra access request. Storing the record digitally means it is retrievable in seconds. None of this is complicated; it just needs to be done and logged.
Staying on top of legionella assessments, gas safety renewals, EICRs, and PAT tests across even a small portfolio is genuinely time-consuming when records live in different places. Prop-pocket gives you a single dashboard where every compliance document sits against the right property, with automated reminders that fire at the right moment in the tenancy cycle.
Prop-pocket is not a testing or inspection provider. What it does is remove the admin burden: store your completed assessments, attach temperature logs and photos, set review reminders tied to tenancy events, and let you export a clean compliance record when an inspector asks for it. The features page shows exactly how document storage and compliance tracking work in practice. Your first property is free to manage, with no setup fee and no long-term contract. Get started with Prop-pocket and have your legionella records organised before the next tenancy begins.
The sources below are the authoritative starting points for legionella compliance in the UK. Keep links to the originals when storing your records, so you can demonstrate the guidance you followed.
Local councils operating selective or additional licensing schemes sometimes require landlords to submit a legionella assessment as part of the licence application. Check your local authority's licensing conditions alongside the HSE guidance above.
This article provides general information for UK landlords and is not a substitute for professional legal or health and safety advice. Confirm current requirements with the HSE or a qualified adviser before relying on any specific guidance.
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