What should be in a cooling tower log book?

If an inspector or environmental health officer visits your site to talk about your cooling towers, the first thing they'll ask for probably won't be to see the tower. It'll be the log book. That folder (or folder of PDFs) is how you prove the treatment programme is happening, not just that it was planned.

A good log book is also just useful. It's where trends show up, where problems get spotted early and where the next person to look after the site finds out what's been going on. February is a quiet month for most towers, so it's a good time to give yours a once-over. Here's what should be in it.

What ACOP L8 says about records

ACOP L8 expects the duty holder to keep records that show Legionella risks are being managed. In broad terms, that means records of:

• the people responsible for carrying out the risk assessment and managing and implementing the written scheme,
• the significant findings of the risk assessment,
• the written scheme and details of how it's being put into practice, and
• the results of any monitoring, inspection, tests or checks, with the dates they were done.

On how long to keep them: ACOP L8 says monitoring, inspection, test and check records should be kept for at least five years. Records such as the risk assessment and written scheme should be kept for as long as they're current and for at least two years after that. If in doubt, keep them. Storage is cheap; missing records aren't.

A sensible layout

There's no single official format, but a log book that's laid out logically makes life easier for everyone. Here's how we'd suggest organising it.

1. Contacts and responsibilities

The duty holder, the responsible person appointed to manage Legionella control (and their deputy), your water treatment contractor and anyone else with a defined role. Include how to reach them out of hours. If the responsible person changes, update it the same week.

2. System description and drawings

What you've got: number and type of towers or evaporative condensers, where they are, approximate water volumes, what they serve, dosing and bleed arrangements, and sample points. A simple schematic is worth a lot, especially to a new engineer on their first visit.

3. Risk assessment and written scheme

The current Legionella risk assessment and written scheme, with any action plan and evidence that actions have been closed out. Keep superseded versions too, filed separately.

4. Notification

A copy of the notification to the local authority under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992, plus any updates. We wrote about this in do you need to notify the council?

5. Routine monitoring

This is the bulk of the book:

• Weekly dip slide or TVC results, with the date taken and date read
• Chemistry results: conductivity, pH, biocide and inhibitor levels, hardness and so on, as your scheme specifies
• Dosing checks: drum levels, pump operation, controller readings and bleed operation
• Legionella sample certificates from the UKAS-accredited lab
• Visual inspection notes on the tower's condition

Results are much more useful with the action levels printed next to them, so whoever fills in the sheet can see straight away if something's out of range.

6. Cleaning and disinfection

Certificates or reports for every clean and disinfection, showing what was done, chemical levels and contact times, and what was found. HSG274 Part 1 expects cooling towers to be cleaned and disinfected at least twice a year, so an inspector will look for at least two of these each year.

7. Corrective actions

Every out-of-range result or fault, what was done about it, by whom, and when it was closed out. This section often tells an inspector more about your site than anything else.

8. Service visits and maintenance

Service reports from your treatment contractor, calibration records for controllers and probes, and records of repairs to fill, drift eliminators, fans and pumps.

9. Training and competence

Evidence that the people doing the checks know what they're doing: training records for site staff who take dip slides or check dosing, and for the responsible person.

10. Chemical safety

COSHH assessments and safety data sheets for the treatment chemicals on site.

The gaps we see most often

• Blank weeks. A missing weekly check is hard to explain afterwards. If a check couldn't be done, write down why.
• Results with no action. A high dip slide recorded, and then nothing. Every out-of-range result needs a note of what happened next.
• Out-of-date risk assessments. The assessment refers to plant that's been replaced, or people who've left.
• Missing cleaning certificates. The clean happened, but nobody filed the paperwork.
• No notification on file. Especially on sites that have changed hands.

Paper or digital?

Either is fine, as long as records are complete, legible, dated, and can be produced when someone asks. Digital log books make trends easier to spot and are harder to lose. Paper is simple and always in the plant room. Plenty of sites use a mix. What matters is that the records exist and someone actually reads them.

Read it, don't just fill it

The most valuable thing a log book does is show trends. A dip slide that creeps up over six weeks, or a biocide drum that's being used more slowly than usual, is your early warning. Ten minutes a month looking back over the last few pages can save a lot of trouble.

Our log books and compliance service sets up and maintains the log book for you, updated on every visit. If yours has got a bit messy, or you've inherited one you don't trust, we're happy to go through it with you.