Legionella Risk Assessments in Pinner

Legionella Risk Assessments in Pinner: what is different here

Affinity Water's 2025 figures for the zones around Pinner

Pinner is supplied by Affinity Water from three supply zones: Harrow North, Rayners Lane and Northwood. Which one serves a house at Pinner Green or on Pinner Hill depends on the address. Their 2025 water quality reports give two figures that matter for legionella. Water temperature in samples across the zones ranged from 5.2 to 22.7°C in Harrow North and from 5.0 to 24.1°C in Rayners Lane, with averages of about 14.5 to 15°C. HSE guidance puts the growth range for the bacteria at 20 to 45°C, and sets a ceiling of 20°C for stored and distributed cold water.

A summer reading above 20°C from the mains is a reminder that a cold tank in a hot loft, or pipes running beside a hot water cylinder, can push it further. The second figure is hardness: 360 mg/l in Harrow North, 348 in Northwood and 268 in Rayners Lane. Scale builds up inside shower heads and hoses and at the bottom of hot water cylinders, and gives bacteria somewhere to settle. So a Pinner assessment pays as much attention to showerheads and cylinder temperatures as to the tank.

Loft tanks and cylinders in Pinner's interwar houses

Pinner's Metro-land houses, Pinnerwood Park's among them, went up with gravity-fed water: a galvanised or plastic cistern under the roof supplying a copper cylinder on the landing. Plenty have since gone over to a combi, yet the bigger houses with two or three bathrooms often kept a cylinder, as a single combi cannot run several showers together. Where the stored system remains, we check the tank's lid, insulation and condition, the stored temperature in the cylinder (the HSE's example is 60°C), and pipework left behind when bathrooms moved.

Redundant pipework is one of the items the HSE asks landlords to remove. A loft conversion often moved or removed the tank, so we also look at what the conversion left in the eaves.

Bathrooms that sit unused in larger Pinner houses

A detached house in Pinner or Hatch End, let to a small family, can have a loft en suite, a guest shower room and a cloakroom basin that go weeks without use, plus an outside tap and perhaps a sink in a garden room. HSE advice is that every tap and shower should run at least weekly. Our assessment names each quiet outlet, gives the tenant a simple weekly flushing routine, and suggests removing an outlet nobody needs, together with its pipe run, so that no dead leg is left behind.

Empty Pinner lets and long gaps between tenancies

Water standing in a closed house is the classic risk. For vacant properties, the HSE suggests a flushing regime, or draining the system if it will stand empty for a long time, and flushing through before a new tenant moves in. In Pinner, longer voids often coincide with work: a kitchen refit, remedial electrics after an EICR, or a wait for a planning decision on windows in a conservation area.

If we are already in the property for the void work, we run every outlet and record it in the photo report, so your file shows the system was flushed before the tenancy began.

Shared houses and converted flats in Pinner

Harrow's HMO conditions and amenity standards contain no specific legionella condition; we checked the May 2020 version that forms part of every Harrow HMO licence. North Harrow is Harrow's too, so the same applies there; over the boundary in Eastcote, Hillingdon's licence is the one to read. The duty comes from general health and safety law, which applies to every landlord. In a shared house, more showers and more occupants mean more spray, and a house let by the room may still run from a single cylinder and tank.

Older houses split into flats sometimes keep one loft tank serving more than one flat, which needs clear ownership: whoever controls that tank should cover it in their assessment. Writing the findings down is a legal requirement only where five or more people are employed, yet for any shared house we put ours in writing and date it.

Official sources

• Affinity Water: Rayners Lane supply zone (AF055) water quality report, 2025
• HSE: legionella, landlords' responsibilities
• HSE: managing legionella in hot and cold water systems (temperature control)
• Harrow Council: HMO conditions and amenity standards (version 5, May 2020)

Last reviewed October 2026 by EliteShires Property Services.