An inspector never watches you flush an outlet. A coroner never sees a temperature being taken. What they see is the record — and if it is thin, contradictory or written the night before, a well-run water system and a neglected one look identical on paper.
That is the uncomfortable part of Legionella record keeping. The hard work is rarely the checking; it is producing an evidence trail that still makes sense to someone who wasn’t there — an auditor, a new responsible person taking over, or an investigator after a suspected case. Most record keeping mistakes are not laziness. They are small shortcuts that look harmless until the day someone reads the file closely.
Before the list, the standard to measure against. L8 expects duty holders to keep records of the risk assessment, the written control scheme and the monitoring that shows it is working, and to have competent people managing it [1]. A good entry answers four questions about every control: who did it, when, what the result was, and what happened if the result was wrong. Hold each mistake below up against those four and the fix is usually obvious.
The shortcuts that sink an audit
1. Logging the task, not the result
What it looks like: a logbook full of ticks and initials — “flushed”, “checked”, “OK” — with no number beside them. What it should look like is covered in keeping records of flushing and sampling activities.
Why it happens: a tick is fast, and on a busy round the reading feels like the dull part of the job.
The fix: record the measured value, not a verdict. A sentinel outlet entry should carry the actual temperature, not “within range”. A number you can trust beats an adjective you can’t — without the figure, you cannot show a trend over time, and you cannot prove the verdict was even true.
2. Readings with nowhere for a failure to go
What it looks like: every reading in range, month after month — which on a real estate is itself a quiet warning — and the one time a temperature came back low, the log simply moves on to the next line.
Why it happens: the form was built to capture results, not responses. There is a column for the reading and nowhere to record what you did about a bad one.
The fix: every out-of-range result needs a visible chain — flagged, who was told, what action followed, when it was re-checked, and when it was closed out. An honest record of a fault you found and fixed is far stronger evidence of control than an unbroken run of perfect numbers. A bad reading with no recorded response is the worst entry in any logbook.
3. Backfilled logbooks and borrowed signatures
What it looks like: a month of entries in one pen, one date, one hand, completed just ahead of an audit. Or one person signing for rounds three colleagues actually walked.
Why it happens: the work slipped, and the paperwork is being reconstructed from memory to look complete.
The fix: record at the point of work, by the person who did it. This is where a digital logbook genuinely helps — a timestamp and user ID captured at the outlet are hard to retrofit, and the edit history exposes any later change. Paper can be perfectly honest too; it simply depends on the discipline that backfilling quietly destroys.
4. Records that don’t name the asset
What it looks like: “TMV serviced”, “tank inspected”, “shower descaled” — with no way to tell which TMV, which tank, which shower, out of the dozens on site.
Why it happens: whoever did the task knew which one they meant. Six months later, nobody does.
The fix: tie every entry to a specific, labelled asset using a consistent ID — the same ID that appears in the risk assessment and the asset register. When an auditor asks for the full history of one outlet, you want to produce it in seconds, not reconstruct it from context and memory.
5. Two sets of books that never reconcile
What it looks like: the contractor holds their service sheets, the site keeps its own log, and nobody has checked that the two agree. Or management runs off a dashboard summary while the asset-level detail underneath has gaps.
Why it happens: responsibility is split, and each party assumes the other holds the complete picture.
The fix: aim for one reconciled record, even when several people feed it. Pull contractor reports into the same system as the in-house rounds, and make sure any summary view drills back down to the underlying entries. A green dashboard you cannot open is decoration, not evidence — there is more on this in audit prep with digital records.
6. Records that die at handover
What it looks like: a change of contractor, a facilities manager moving on, or a switch of system, and a year of history becomes unreadable — locked in someone’s spreadsheet or simply gone.
Why it happens: nobody owns continuity. Records get treated as the current job’s paperwork rather than the building’s permanent memory.
The fix: treat the record as belonging to the building, not the person or the supplier. Agree export and ownership at the start of any contract, and keep records for the periods L8 guidance sets out — commonly several years for monitoring records, and the risk assessment for as long as it stays current plus a period beyond [1]. Confirm the exact figures for your premises rather than guessing at them.
If you change one habit, change this
Record the decision, not just the task. Compare a bare “flushed” with: “This outlet is flushed weekly because it serves a rarely used changing room; a missed flush goes to the responsible person; three misses trigger a review of whether the outlet should stay.” An entry like that survives a change of staff, explains itself to an auditor, and tells the next person why the control exists, not only that it once happened. The frequency itself isn’t lifted from a standard — it comes from your risk assessment, and the record should make that link plain [2].
Where this guidance stops
This is general advice on keeping a defensible record, not a ruling on what your specific scheme must contain. What counts as adequate evidence, how long you hold it, and what an acceptable result looks like are all set by your site’s risk assessment and the people competent to interpret it. And don’t let a clean lab certificate stand in for the day-to-day control records — a negative sample describes one outlet at one moment, and HSE guidance ties testing to what your risk assessment calls for, not to producing a reassuring document for the file [3]. If a record might end up in an enforcement file or an incident investigation, take advice on it rather than leaning on a checklist like this one.
Common questions
How long do I need to keep Legionella records?
There is no single number that covers everything. L8 guidance points to keeping records of monitoring and inspection for a period of years, and keeping the risk assessment record for as long as it remains current plus a period afterwards [1]. The safe approach is to confirm the retention periods that apply to your premises, and never destroy a record while it could still matter to an investigation or a handover.
Are digital logbooks acceptable, or does the HSE expect paper?
Format is not the test — content and integrity are. The HSE expects you to keep records showing that precautions, monitoring and management arrangements are real and working [1]. A digital logbook is acceptable, and usually stronger, because timestamps, user IDs and edit history are harder to fake than a paper page filled in afterwards. Paper is fine too, as long as it is complete and written at the time.
If my contractor keeps all the records, am I still responsible?
Yes. You can hand the tasks to a contractor; you cannot hand over the duty. The duty holder stays accountable for control and for the records that prove it, so you need ready access to those records and a way to confirm they are complete [1]. A contract that leaves the evidence solely inside someone else’s system is a gap, not a delegation.
Sources
[1] HSE, “Legionnaires’ disease. The control of legionella bacteria in water systems - Approved Code of Practice and guidance (L8)”. https://www.hse.gov.uk/pubns/books/l8.htm [2] HSE, “Legionnaires’ disease: Technical guidance (HSG274)”. https://www.hse.gov.uk/pubns/books/hsg274.htm [3] HSE, “Testing and monitoring your water system for legionella”. https://www.hse.gov.uk/legionnaires/testing-monitoring-water-system.htm