Legionella Risk Assessments for Landlords: A Guide

Legionella is a type of bacteria that grows in stagnant water between 20-45°C. If it gets into water droplets that someone inhales — from a shower, tap, or cooling system — it can cause Legionnaires' disease, a severe form of pneumonia that kills about 10% of those infected.

As a landlord, you have a legal duty to assess and control the risk of legionella in your rental properties. Here's what that actually involves.

What the law requires

Your obligation comes from two pieces of legislation:

1. Health and Safety at Work etc. Act 1974 — places a general duty on landlords to ensure the health and safety of tenants, so far as is reasonably practicable
2. Control of Substances Hazardous to Health Regulations 2002 (COSHH) — requires you to assess and control risks from hazardous substances, including biological agents like legionella

The Health and Safety Executive (HSE) has published specific guidance for landlords in ACOP L8 and the simplified guidance document HSG274 Part 2, which covers hot and cold water systems in domestic properties.

The requirement applies to all rented properties in England and Wales, regardless of property type, tenancy type, or whether the property has gas. It also applies to Scotland and Northern Ireland under equivalent health and safety legislation.

What a legionella risk assessment involves

For a typical domestic rental property (house or flat with a standard combi or system boiler), a legionella risk assessment is straightforward. It checks:

• Hot water temperature — the hot water system should store water at 60°C or above and distribute it at 50°C or above within one minute of running the tap. Legionella thrives between 20-45°C; temperatures above 60°C kill it.
• Cold water temperature — cold water should be below 20°C. If cold water pipes run through warm spaces (airing cupboards, near boilers), they may warm up enough to enter the danger zone.
• Dead legs — sections of pipework that are rarely used, where water can stagnate. Common in properties where a bathroom has been removed or a tap capped off.
• Water storage — open water tanks (common in older properties with a traditional system boiler) can accumulate sediment and allow bacterial growth. They should have fitted, close-fitting lids.
• Showerheads and taps — limescale and biofilm can harbour legionella. Showerheads are the primary transmission risk because they create aerosols (tiny water droplets that can be inhaled).
• Void periods — water that sits in pipes during empty periods between tenancies is a risk. Systems should be flushed before a new tenant moves in.

Can you do the assessment yourself?

Yes. The HSE does not require you to hire a professional for standard domestic properties. Their guidance for landlords explicitly states:

"For most domestic hot and cold water systems the risk of legionella is low. Where landlords can demonstrate that they have assessed the risks as low... no further action may be needed."

For a typical property with a combi boiler (which heats water on demand with no storage tank), the risk is generally low. You can complete the assessment yourself by:

1. Checking water temperatures at representative taps
2. Identifying any water storage tanks and checking their condition
3. Looking for dead legs or unused outlets
4. Noting whether showerheads are clean and free of heavy limescale
5. Recording your findings and the date

If your property has a complex water system — a large hot water cylinder, multiple water tanks, a shared supply, or if it's an HMO — consider hiring a professional. Assessments from qualified assessors typically cost £50-150 for a standard property.

How often to assess

There's no fixed legal interval, but the HSE recommends reviewing your assessment:

• Every 2 years as a general guideline
• Whenever the water system changes (new boiler, altered pipework, bathroom added/removed)
• Between tenancies — flush the system if the property has been empty for more than a week
• If you receive a complaint about water temperature or quality

What to do with the results

If your assessment identifies risks, common actions include:

Risk Found	Action
Hot water below 50°C at taps	Increase boiler thermostat or cylinder stat to 60°C+
Cold water above 20°C	Insulate cold pipes running through warm areas
Open/damaged water tank lid	Fit a close-fitting lid, clean tank
Stagnant dead legs	Remove or regularly flush unused pipework
Heavy limescale on showerheads	Descale or replace; clean quarterly
Property void for 7+ days	Flush all outlets for 2 minutes before new tenant moves in

Record keeping

Keep a written record of your assessment, including:

• Date of assessment
• Who carried it out
• Findings and risk level (low/medium/high)
• Any actions taken
• Date of next review

You should keep records for the duration of the tenancy and a reasonable period after (5 years is standard practice). If the HSE or local authority investigates a case of Legionnaires' disease linked to your property, your records demonstrate that you took reasonable steps.

Penalties for non-compliance

Enforcement sits with the HSE and local authority environmental health teams. Penalties are serious:

• HSE improvement notice — legally requiring you to take specific action within a set timeframe
• HSE prohibition notice — can prevent you from letting the property until the risk is controlled
• Prosecution under HSWA 1974 — unlimited fines and up to 2 years' imprisonment
• If a tenant contracts Legionnaires' disease — potential manslaughter charges in the most serious cases

In practice, prosecutions are rare for standard domestic properties where the landlord has made a reasonable effort. The HSE focuses enforcement on persistent non-compliance and cases where someone is harmed.

Common mistakes

• Ignoring it because "it's just a domestic property" — the legal duty applies to all rental properties, not just commercial buildings or HMOs. The HSE has brought enforcement action against individual landlords.
• Doing the assessment once and never revisiting — circumstances change. A new boiler installation, a bathroom conversion, or a long void period all change the risk profile.
• Assuming a combi boiler means zero risk — combi boilers are lower risk than systems with stored water, but they don't eliminate risk entirely. Showerheads and dead legs still need checking.
• Not flushing after void periods — if a property sits empty between tenancies, water stagnates in the pipes. Run all taps and showers for at least 2 minutes before a new tenant moves in.

Tenant responsibilities

Once the assessment is done and any issues are addressed, your tenants play a role in ongoing control:

• Running taps and showers regularly (relevant for second bathrooms that aren't used daily)
• Not adjusting the boiler thermostat below safe temperatures
• Reporting any changes in water quality, temperature, or unusual smells

Include these responsibilities in your tenant welcome pack or handbook. You're still responsible for the system itself, but tenants' day-to-day use matters.

How DueProper will help

DueProper will track your legionella risk assessment as part of your full compliance checklist. You'll get reminders before your next review is due and will be able to upload your assessment report as evidence.

Coming soon — join the waitlist for early access.

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This article is for information only and does not constitute legal advice. For the HSE's official guidance on legionella for landlords, see hse.gov.uk/legionnaires/legionella-landlord-responsibilities.htm. The full Approved Code of Practice is ACOP L8.