Legionella Risk Assessments in Ruislip

Legionella Risk Assessments in Ruislip: what is different here

What comes into a Ruislip house from the mains

Ruislip's drinking water comes from Affinity Water's Ruislip supply zone, reference AF087, which served about 60,100 people in 2025. The zone report logged 156 temperature readings that year, from 0.2°C to 23.8°C, with a mean of 15°C. HSE's guidance is that cold water should be kept below 20°C, and the summer peak shows the supply itself can arrive warmer than that.

In a loft tank under a hot roof, it warms further. The same report records total hardness of 320 mg/l, and scale inside a cylinder or around a shower head gives bacteria somewhere to settle. Neither fact makes Ruislip unusual for this part of London; both are why the assessment looks at stored water first.

Loft tanks and airing cupboard cylinders

A typical interwar Ruislip semi was built with a cold water storage tank in the loft feeding a copper cylinder on the landing. Many have since been converted to a combination boiler, which removes most of the stored water; many have not. Where the tank is still there, we check that it has a fitted lid, a screened overflow and insulation, that the water in it is clean and not too warm, and that the cylinder gets hot enough.

A tank left in the loft after a combi conversion, still connected to nothing or to one old cold tap, is a common finding, and draining and disconnecting it is usually the sensible fix.

Shared houses in HA4

A small HMO in a converted Ruislip semi often has an extra shower room or a washbasin fitted in a bedroom during conversion, and some of those outlets go unused for weeks when a room is empty. Long pipe runs to a little-used basin are exactly what the assessment looks for.

We list each outlet, how often it is used, and whether any pipework now leads nowhere. Where a room sits empty between tenants, the simple control is a weekly flush of its taps and shower, which an agent or a remaining tenant can do and note down.

After a let in Ruislip has stood empty

A Ruislip Gardens or South Ruislip let that follows RAF Northolt posting dates can stand empty for a few weeks between occupants, and houses held for sale can sit for months. Before the next tenant moves in, every outlet should be run through, the cylinder brought up to temperature and shower heads descaled or replaced. If the property has been empty long enough for the water to go stale, we can assess on the day of that flush and record what was done.

Flats over shops and converted buildings

If a parade flat on the High Street or Victoria Road takes its water from a tank in the roof space, find out what else that tank feeds. If it serves the shop or another flat as well, it may be the freeholder's to look after. The assessment records what supplies your flat, who controls the tank, and what you can and cannot check yourself, so the responsibility line is written down.

Official sources

• HSE: Legionella and landlords' responsibilities
• Affinity Water: water quality report, Ruislip supply zone AF087, 2025
• Hillingdon Council: Appendix 2, proposed HMO licensing conditions (additional licensing designation papers)
• Royal Air Force: RAF Northolt contact details (West End Road, Ruislip HA4 6NG)
• Nomis: Census 2021 TS044 accommodation type (Ruislip, Ruislip Manor and South Ruislip wards)

Last reviewed October 2026 by EliteShires Property Services.