Legionella Risk Assessments in Hendon

Legionella Risk Assessments in Hendon: what is different here

Shared cold water tanks in converted Hendon houses

When Victorian and Edwardian houses around Brent Street and The Burroughs were split into flats, the original loft tank often stayed, sometimes feeding the cold taps or the hot water cylinder of more than one flat. A shared tank may have a loose or missing lid, insulation that has slipped, debris or a dead bird in it, and a draw-off so slow in a lightly used flat that water sits for days.

We record who controls the tank, what it feeds and what condition it is in. If it serves more than one flat, the freeholder or the person controlling the common parts carries the duty for it, so the assessment says that plainly.

Hot water cylinders in shared houses

Barnet's adopted HMO standards say that where the landlord supplies heating and hot water centrally, it must be usable at any time. In a five-bedroom student house that usually means a vented cylinder heated by a system boiler, sometimes with an immersion as backup. The two checks that matter most are whether the stored water reaches 60°C and whether the hot taps reach 50°C within a minute or so.

Showers fitted in former bedrooms at the far end of a long pipe run are the usual weak point, along with a little-used basin in a box room.

Summer voids near Middlesex University

Student lets around the university often sit empty for weeks between one tenancy and the next. Standing water is the classic legionella risk, so the plan we leave covers what to do at the end of a void: run every hot and cold outlet, starting with the one furthest from the tank, descale and disinfect shower heads, and check the cylinder temperature before anyone moves in. If an agent is handling the turnaround, we write the steps so the person with the keys can follow them and record the date.

Water temperature and very hard water

Affinity Water's 2025 report for its Colindale and Kingsbury zone, next to Hendon, recorded cold water between 6.2°C and 23°C across 228 samples, with a mean of 14.7°C, and total hardness of 333 mg/l. Which company supplies a Hendon address varies, so check your bill. At the top of that range in summer, cold water stored in a warm loft can move towards the 20°C to 45°C band in which legionella bacteria multiply.

Very hard water also scales shower heads and cylinder elements quickly, and scale gives bacteria somewhere to settle, so descaling appears in most of our Hendon action plans.

West Hendon heat-network flats and combi flats

At the 2021 Census, 4.6% of West Hendon households were heated by a district or communal network, and Hendon Waterside takes its heat from an energy centre in the basement of Block E2. In a flat on that network, the heat network and its plant are managed by the operator, so the flat assessment looks at what is inside the front door: outlet temperatures, any thermostatic mixing valves, little-used outlets and shower heads. A post-war or new-build flat with a combi boiler and no stored water is normally low risk, and the assessment for it is short.

Official sources

• HSE: landlords' legionella duty and no certificate requirement
• Affinity Water 2025 temperature and hardness, Colindale/Kingsbury zone
• Barnet HMO standards: centrally supplied hot water usable at any time
• Hendon Waterside heat network from the Block E2 energy centre
• Census 2021 heat network share in West Hendon
• Middlesex University campus on The Burroughs

Last reviewed October 2026 by EliteShires Property Services.