Legionella isn’t the most talked-about landlord responsibility, but it’s one of the clearest — every landlord has a legal duty to assess and manage the risk in their water systems, regardless of property size or type. Here’s a practical, plain-English guide to what that actually involves.
What Legionella Actually Is
Legionella is a bacterium found naturally in water sources, including the water systems inside buildings. It becomes a health risk when it grows to dangerous levels and gets inhaled — usually through fine water droplets from showers, taps, or other aerosol-producing fixtures — potentially causing Legionnaires’ disease, a serious and occasionally fatal form of pneumonia.
The bacteria thrive in water sitting between roughly 20°C and 45°C, particularly where the water is stagnant, and are killed at temperatures above 60°C. That temperature range is the whole basis for how the risk is managed in practice.
What the Law Actually Requires
Legionella management sits under the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health (COSHH) Regulations, with the HSE’s Approved Code of Practice L8 setting out the recognised standard for compliance. In practical terms, this means every landlord — residential or commercial — has a legal duty to:
- Identify and assess the risk of legionella in the property’s water system
- Implement proportionate control measures to manage that risk
- Keep appropriate records, particularly for larger or higher-risk systems
- Review the assessment periodically, and whenever something changes — a change of tenant, a period the property sat empty, or alterations to the water system
Crucially, this applies whether the property is a single let, an HMO, or a larger commercial or social housing portfolio — the legal duty doesn’t disappear because a building is small or simple.
What a Legionella Risk Assessment Actually Involves
A proper risk assessment isn’t a form-filling exercise — it’s a genuine review of the property’s water system, covering:
Identifying the water sources. Cold water storage tanks, hot water cylinders, taps, showers, and any other outlets that could create aerosols.
Assessing risk factors. Water temperature, how often each outlet is used, any dead legs or infrequently used pipework, and the presence of scale, sludge, or biofilm that legionella can feed on.
Recommending control measures. This is usually straightforward for most residential properties — keeping hot water above 60°C at the cylinder, cold water below 20°C, and flushing outlets that aren’t used regularly.
Setting a review schedule. Most low-risk domestic properties don’t need re-testing constantly, but the assessment itself should be reviewed periodically and after any relevant change to the property or its occupancy.
The Properties Where This Matters Most
While every landlord carries the duty, risk genuinely increases in certain situations: properties that sit empty between tenancies, buildings with more complex or older pipework, HMOs and larger blocks with shared water systems, and any property with underused outlets — an unused shower in a spare room is a classic example of exactly the kind of stagnant water legionella favours.
This overlaps closely with wider commercial plumbing compliance, where legionella sits alongside gas safety and backflow prevention as one of the core water-related duties landlords need to stay on top of.
Why This Isn’t Just a Compliance Formality
Legionnaires’ disease is a genuine, serious illness — this isn’t a box-ticking exercise dressed up as a legal requirement. Beyond the safety case, a properly documented risk assessment protects landlords from enforcement action, supports insurance claims, and demonstrates that a property is being managed responsibly should anything ever be questioned.
Getting a Proper Assessment Done
The value of a legionella risk assessment depends entirely on whether it’s carried out properly — a superficial check that misses a stagnant outlet or an incorrect cylinder temperature isn’t worth much more than not having one at all.
Our plumbing and heating services include legionella risk assessments as part of a wider compliance approach for landlords and property managers across Bristol and the South West. If you’re not sure when your property was last assessed, or you’re taking on a new tenancy and want it done properly, get in touch with the Lime Construction team.