Wales Landlord Legionella Risk Assessment

What the Law Requires

Under the general duty of care and the Health and Safety at Work etc. Act 1974, landlords must assess and control the risk of Legionella bacteria in the water systems of properties they let. This applies across the UK, including Wales, and overlaps with Hazard 18 (Water Supply) in the 29 statutory matters under the Renting Homes (Fitness for Human Habitation) (Wales) Regulations 2022.

The good news for most private landlords: in a standard domestic property with a direct mains water feed and a combi boiler, a visual risk assessment is usually sufficient. You do not need laboratory water testing unless high-risk factors are present.

What a Visual Risk Assessment Covers

For a typical house or flat with mains-fed cold water and a combi or system boiler, the assessment is a structured walk-through checking for conditions that allow Legionella to grow:

• Dead legs — sections of pipework that no longer serve an outlet (a capped-off pipe from a removed appliance). Stagnant water in dead legs is the primary domestic Legionella risk.
• Cold water storage tanks — particularly in older properties with a header tank in the loft. The tank must have a fitted, close-fitting lid, and insulation to keep the water below 20°C.
• Hot water temperature — stored hot water should be maintained at 60°C or above at the cylinder, and delivered to outlets at no less than 50°C. Combi boilers heat on demand and generally do not store water, so this is less of a concern.
• Infrequently used outlets — a bathroom in a spare room or an outdoor tap that runs only occasionally. Standing water in these pipes can harbour bacteria.
• Showerheads and hoses — warm, moist environments with aerosol generation. Limescale build-up inside showerheads creates a biofilm that supports Legionella growth.

Record the date of the assessment, what you checked, and what you found. If everything is low-risk (mains-fed, combi boiler, no dead legs, no tanks), the assessment is complete and the risk is controlled.

When Laboratory Testing Is Needed

Laboratory water sampling is not usually needed for domestic hot and cold water systems. A specialist may recommend it in specific circumstances identified by the risk assessment, for example:

• The property has a large cold or hot water storage tank (common in older properties and converted flats)
• There are known dead legs that cannot easily be removed
• The property has been vacant for an extended period and water has stagnated; use a suitable flushing or draining regime, and sample only if the risk assessment indicates it
• A vulnerable occupier is moving in (immunocompromised individuals are at higher risk)
• A previous sample returned a positive result

If you commission laboratory testing, a water hygiene specialist takes samples from hot and cold outlets and the results typically come back within 7–10 days. Interpret the results in the context of the system and risk assessment, following the HSE technical guidance and the specialist's advice; there is no single action threshold for every domestic property.

Practical Steps Between Tenancies

The highest-risk period for Legionella is during a void — when the property is empty and water sits in the pipes without being drawn. Before a new contract-holder moves in:

1. Flush all taps and showers before the new contract-holder moves in
2. Run the hot water system up to operating temperature
3. Clean and descale showerheads
4. Check that any stored hot water is reaching 60°C at the cylinder
5. Remove any dead legs identified during your risk assessment

These steps take 15 minutes during a pre-let inspection. Record the date and include it in your compliance file.

How This Connects to Welsh Fitness Law

A contaminated water supply falls under Hazard 18 (Water Supply) of the 29 statutory matters. If the water system poses a health risk — whether from Legionella, lead pipework, or inadequate pressure — the dwelling can be declared unfit for human habitation under Section 91 of the Renting Homes (Wales) Act 2016.

The practical risk for most standard domestic properties is low, but the assessment must still be done. Keeping a dated record is prudent, although health and safety law does not generally require a domestic landlord to document the assessment findings. A landlord who can show they assessed the Legionella risk, maintained the hot water system, and flushed the pipes between tenancies has a much stronger position than one who never considered it.

The Fitness for Human Habitation compliance guide includes a Property Self-Inspection Checklist that covers water safety alongside all 29 hazard categories — so the Legionella check is part of your routine inspection, not a separate task that gets forgotten.

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