Legionella Risk Assessments for Scottish Landlords

Overview & Key Takeaways

Under Section 3(2) of the **Health and Safety at Work etc. Act 1974** and the **Control of Substances Hazardous to Health (COSHH) Regulations 2002**, private residential landlords have a statutory legal duty to assess and control the risk of exposure to **Legionella bacteria** in domestic water systems.

Legionnaires\u2019 disease is a potentially fatal form of pneumonia caused by inhaling aerosolized water droplets containing Legionella bacteria. In domestic rental properties, water systems that allow water to stagnate between **20\u00b0C and 45\u00b0C** create conditions for bacterial proliferation.

Why Old Conventional Systems Present High Legionella Risks

Properties operating traditional gravity-fed heating systems (with attic cold water tanks and copper cylinders) contain multiple hazard zones: - Attic Cold Water Storage Tanks: Frequently unlagged, open to airborne dust, and warm during summer months, allowing water to sit at 25\u00b0C to 30\u00b0C. - Hot Water Storage Stratification: Copper cylinders where the thermostat is set too low (under 50\u00b0C), or where the bottom of the cylinder remains lukewarm, allowing bacteria to multiply. - Dead Legs: Redundant pipework leading to capped-off sinks or unvented expansion pipes where water sits stagnant for weeks.

How a Combi Conversion Eliminates 90% of Legionella Hazards

When you convert an older property to a modern unvented condensing combi boiler: 1. Zero Storage: The cold water storage tank in the attic and the hot water cylinder in the cupboard are decommissioned and removed. 2. Direct Mains Supply: Water travels directly from the cold water mains into the boiler\u2019s compact plate heat exchanger under high pressure, without resting in open cisterns. 3. Instantaneous Thermal Pasteurization: Combi boilers heat water instantaneously to 55\u00b0C\u201360\u00b0C as it passes through the burner, instantly killing any aquatic bacteria before water reaches shower heads.

Practical Steps for Scottish Landlords

You do not need to pay commercial laboratories hundreds of pounds for water samples. A simple, compliant Legionella assessment requires: - Checking that hot water reaches at least 50\u00b0C within 1 minute of opening outlets. - Checking that cold water runs below 20\u00b0C within 2 minutes. - Descaling shower heads and hoses every 6 months to eliminate mineral biofilms. - Flushing water outlets thoroughly between tenancies.

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