Legionella Risk Assessments in Wembley

Legionella Risk Assessments in Wembley: what is different here

What Affinity's Wembley zone figures mean for risk

Wembley's water comes from Affinity Water's Wembley supply zone, AF062, which served a population of 61,209 in 2025. Across 157 temperature samples that year, the water ranged from 7.3°C to 24.5°C, with a mean of 15.4°C. HSE says legionella grows between 20°C and 45°C and that cold water should be kept below 20°C. So on a warm summer day, mains water can already be above that line as it enters a Wembley property, before it has sat in a warm riser or a loft tank.

The same report gave hardness of 295 mg/l, and scale inside shower heads and mixing valves gives bacteria a surface to hold on to.

Flats in heated towers near the stadium

In a Wembley Park tower, the communal tanks, booster pumps and risers are the building's responsibility and fall under the freeholder's own water risk assessment. Yours covers the flat. The local risk there is heat: cold pipes run through warm ceiling voids and service cupboards beside heating pipework, and in summer the cold tap can run warm for some time.

We measure how long each cold outlet takes to fall below 20°C and each hot outlet to reach 50°C, check little-used outlets such as a second shower room, and look at the thermostatic mixer. If the cold supply stays warm, we record it for the managing agent rather than treat it as your fault.

Cylinders and loft tanks in interwar houses

Many of the gas-heated semis in Tokyngton and Barnhill, and around Preston Road and North Wembley, still have a hot water cylinder and a cold water tank in the loft, or had them until a combi went in. Stored hot water should reach 60°C, a loft tank needs a tight lid and insulation to keep out debris and summer heat, and pipes left behind after a combi conversion can become dead legs where water sits.

Hard water makes the first of those harder, because scale on an immersion element or cylinder coil slows heating. We look at all three and write down what needs changing.

Event lets and voids that sit empty

A flat let only on stadium weekends, or a house empty between tenancies, is the classic case HSE warns about: water standing in pipes and shower hoses. HSE's advice is that outlets in a vacant property should be used at least once a week, and that the system should be flushed before it is occupied again. For short lets we write a simple flushing routine for the cleaner to follow between guests, and for voids we include it in the assessment so the agent can tick it off.

What Brent's licences say, and do not say

Neither Brent's selective conditions nor its HMO conditions mention legionella by name. The duty comes from health and safety law and HSE's guidance, and recording findings is not always required. The HMO conditions do require hot and cold water to be constant and available at every bath, shower and basin, so a system run cold to save energy, or left with a failed immersion, can become a licence matter too, particularly in the shared houses of Wembley Central and Wembley Hill.

A written assessment shows a Brent inspector, or a tenant, that the risk has been considered.

Official sources

• Wembley zone AF062 temperature, hardness and population, Affinity Water 2025
• HSE on landlords' legionella duties and the absence of a certificate
• HSE temperature benchmarks for hot and cold water
• Brent HMO amenity standards on hot and cold water supplies
• Gas-heated homes in Tokyngton and Barnhill, Census 2021

Last reviewed October 2026 by EliteShires Property Services.