What should a legionella log book contain?

A legionella log book records the monitoring your written scheme requires: sentinel temperatures, flushing of little-used outlets, thermostatic mixing valve and shower checks, tank and calorifier inspections, and any remedial action taken. It is the evidence the scheme is being followed, not a separate exercise on its own.

The risk assessment says what could go wrong. The written scheme says how you will prevent it and how often. The log book is where you show that the tasks actually happened, on the dates they were due, by the people named to do them. This page covers what a good template contains, what to record on each sheet, and how long to keep it.

The log book is evidence, not paperwork

Under the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations, a duty holder has to manage the risk from legionella and be able to demonstrate that management. ACOP L8 and HSG274 set out the monitoring; the log book is where the results live.

When an environmental health officer or HSE inspector visits, they do not watch you take a temperature. They ask for the log book. A complete, current record tells them the scheme is live. Gaps tell them the opposite, and a run of empty flushing rows is one of the more common triggers for enforcement, because it shows a control was scheduled and then quietly dropped.

What a good log book template includes

A template is only as useful as the columns it forces you to fill. Each recurring task in the written scheme should map to its own sheet, and each sheet should capture enough that a stranger could audit it a year later.

Monthly temperature record (sentinel outlets)

The core sheet. For the sentinel outlets, the nearest and furthest on each hot and cold circuit, record the date, outlet reference, the hot temperature after running for one minute, the cold temperature after two minutes, and the initials of the person taking the reading. The targets to check against are hot reaching 50°C (55°C in healthcare) within one minute and cold staying below 20°C. A temperature chart makes the pass and fail bands easy to read at a glance, and temperature control is the primary defence in most systems.

Flushing record (little-used outlets)

Any outlet used less than roughly once a week needs regular flushing, usually weekly. The sheet records the outlet reference, the date, how long it was run, and the initials of whoever did it. This is the sheet inspectors scrutinise hardest, because it is the easiest to let slip. See flushing outlets for how long to run each type.

Quarterly TMV and shower checks

Thermostatic mixing valves and showers get their own periodic entries. Record TMV inspection and, where due, servicing, plus the descale and disinfection of shower heads and hoses. Note the date, the asset reference, what was done, and the outcome. Both link out to detail: TMV servicing and cleaning shower heads.

Tank and calorifier inspections

Annual (or as scheduled) inspections of the cold water storage tank and the calorifier. Record the date, the condition found, any cleaning or disinfection carried out, and the flow and return temperatures for the calorifier. Photographs filed alongside the entry help evidence condition over time.

Remedial action log

Whenever a reading misses target or a sample comes back above the action level, the response goes here: what was found, what was done, by whom, when, and the follow-up result that confirms it is resolved. This sheet ties directly to what to do if legionella is detected.

Review log

A short record of when the risk assessment and scheme were reviewed, who reviewed them, and what changed. It shows the system is being kept current rather than filed once and forgotten.

That is the discipline the whole log book turns on. A temperature you took but never recorded protects no one, because you cannot produce it. The record is what converts routine work into a defensible position, and it is also what lets you spot a slow drift, a calorifier that reads a degree cooler each month, before it becomes a failure.

How long to keep legionella records

The usual guidance is to retain monitoring records for at least five years. That is a minimum, not a target. In practice many duty holders keep them longer, particularly where there has been a positive sample, an outbreak investigation, or where the records may be needed for an insurance claim or a property transaction.

Healthcare premises working to HTM 04-01 keep water safety records for far longer, often for the life of the asset, which means decades rather than years. Both paper and electronic records are acceptable. What matters is that the record is legible, has a clear audit trail of who entered what and when, and can be produced promptly on request.

What the template does not do

A log book template is a recording tool. Filling it in does not make a system safe and it does not, on its own, make you compliant. It evidences that the tasks in your scheme were carried out; it cannot tell you the scheme itself is adequate for your building, and it cannot substitute for a competent risk assessment. If the wrong outlets are being monitored, or a risk has been missed, a perfectly kept log book will still record the wrong things faithfully.

Used properly, though, it is the backbone of legionella compliance: the day-to-day proof that sits under the risk assessment and the written scheme. If you have not drawn the scheme up yet, our written scheme template gives you the framework to record it. For the structure of a full book, section by section, see the log book guide, and start recording with the free risk assessment and log template.