The Legionella Written Scheme: Monitoring, Temperatures and Records
- The written scheme sets out the control measures, who carries them out, how often, and how results are recorded. It is a legal requirement under L8.
- For hot and cold water systems the core controls are temperature: hot water stored at 60°C and reaching 50°C at outlets within a minute, cold water below 20°C.
- Routine monitoring is monthly temperature checks at sentinel outlets, weekly flushing of little-used outlets, quarterly shower-head cleaning and annual tank inspection.
- Records must be kept, typically for at least five years, and are what an inspector or insurer will ask to see.
A legionella risk assessment with no written scheme behind it is a diagnosis without a treatment. L8 requires the duty holder to have a written scheme for preventing or controlling the risk, and HSG274 tells you what goes in it: who is responsible, what temperatures to hold, what to flush and clean and how often, and how to record it. Here is what a workable scheme looks like.
What the scheme contains
- A schematic of the water system, up to date.
- Who is the duty holder, the responsible person and any contractors, with contact details.
- The control measures: temperatures, flushing, cleaning, disinfection, any water treatment.
- The monitoring programme: what is checked, where, how often, by whom.
- The checks to confirm the scheme is working, and what to do when results are out of range.
- How and where records are kept.
The temperature controls
HSG274 Part 2 sets the targets most schemes are built on. Hot water should be stored at 60°C or above and reach at least 50°C at the outlet within a minute of running (55°C in healthcare). Cold water should be stored and distributed below 20°C, reaching that within two minutes of running. Legionella multiplies between roughly 20°C and 45°C, so these targets keep water out of the growth zone. Where thermostatic mixing valves are fitted to prevent scalding, the system upstream still needs to meet the temperatures.
The monitoring routines
| Task | Frequency |
|---|---|
| Temperature checks at sentinel outlets (nearest and furthest from the calorifier) | Monthly |
| Flush little-used outlets | Weekly |
| Dismantle, clean and descale shower heads and hoses | Quarterly |
| Check calorifier flow and return temperatures | Monthly |
| Inspect cold water storage tanks | Annually |
| Representative outlet temperatures across the system | Annually |
The assessment may add tasks for particular risks; these are the common baseline.
Get a scheme in place
Match with competent legionella assessors and monitoring providers who cover your area. No-obligation quotes.
Who does what
Many businesses do the monthly and weekly checks in-house with a trained member of staff and a calibrated thermometer, and contract the quarterly and annual tasks. Others contract the whole programme, often inside a maintenance contract. Either way, the scheme must name who is responsible for each task and what happens if they are absent.
Records
A legionella logbook, paper or digital, holding the assessment, the scheme, each monitoring result with date and person, any out-of-range results and the action taken, and contractor reports. Retain records for at least five years. When an HSE inspector or your insurer asks whether you control legionella, the logbook is the answer.
Getting a scheme written
A competent assessor produces the scheme as part of the risk assessment. ComSurv matches you with assessors and monitoring providers who cover your area, with no-obligation quotes.
Sources & further reading
- HSE HSG274 Part 2: hot and cold water systems — the temperatures and routines
- HSE ACoP L8 — the requirement for a written scheme
External links open in a new tab. ComSurv is a matching service, not a firm of surveyors, and is not affiliated with these organisations. This article is general information, not legal, surveying or valuation advice; take advice on your specific situation.
