Routine monitoring & Legionella sampling
Weekly and monthly checks, dip slides, chemistry testing and quarterly Legionella samples sent to a UKAS-accredited laboratory. The evidence that your programme is working.
You can't control what you don't measure.
Monitoring is how you, and anyone inspecting you, know the treatment programme is actually working. HSG274 Part 1 sets out what should be checked and how often: microbiological activity at least weekly, chemistry on a regular cycle, and Legionella sampling at least quarterly.
We can do all of it, or split it with your site team. Plenty of clients have their own engineers run the weekly dip slides while we handle the chemistry, the lab samples and the interpretation. Either way, every result goes in the log book and anything out of range gets a clear next step.
Legionella samples go to a UKAS-accredited laboratory, and we explain the results in plain English when they come back. If a result is high, our positive result response service kicks in.
Dip slides and TVC testing
Total viable counts to track general bacterial activity, read and recorded against HSG274 action levels.
Water chemistry testing
Conductivity, pH, hardness, inhibitor and biocide reserves, checked against the targets in your programme.
Quarterly Legionella sampling
Samples taken correctly, chilled and sent to a UKAS-accredited lab, with results explained when they arrive.
Visual inspection
A look at the tower, pond, drift eliminators, fill and dosing kit on every visit.
Site team training
If your engineers do the weekly checks, we'll show them how and give them simple record sheets.
Trend reporting
Results tracked over time, so slow drifts get spotted before they become problems.
What gets checked, and how often
Your written scheme sets the actual frequencies, based on your risk assessment. This is the kind of baseline HSG274 Part 1 describes.
| Check | Typical frequency | What it tells you |
|---|---|---|
| Dip slide / TVC | At least weekly | General bacterial activity and whether the biocide regime is keeping up. |
| Biocide and inhibitor reserve | Weekly to monthly | Whether dosing is delivering what the programme needs. |
| Conductivity, pH, hardness | Weekly to monthly | How concentrated the water is and whether it's heading towards scaling or corrosion. |
| Legionella sample (UKAS-accredited lab) | At least quarterly | Direct check for Legionella. More often after a positive result or at commissioning. |
| Cleaning and disinfection | At least six-monthly | Removes the sludge, scale and biofilm that monitoring can't fix. |
Frequencies are a guide. Your risk assessment may call for more, for example on a system with a history of high counts.
Monitoring & Legionella sampling: common questions
How often should a cooling tower be tested for Legionella?
HSG274 Part 1 says Legionella sampling should be carried out at least quarterly, and more often in some situations, such as when commissioning, after a positive result or when the system has been out of control.
What's the difference between a dip slide and a Legionella test?
A dip slide measures the general bacterial count (TVC) and gives a result in a couple of days on site. A Legionella test is a lab analysis for Legionella specifically. You need both: dip slides weekly as an early warning, Legionella samples at least quarterly.
Can our own maintenance team do the weekly checks?
Yes, as long as they're trained and the results are recorded properly. We can train your team and supply record sheets, then pick up the chemistry, lab sampling and interpretation ourselves.
Which lab do you use?
Legionella samples are analysed by a UKAS-accredited laboratory, which is what HSG274 expects. The certificate is added to your records.
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