Failed a Legionella test? Got an EMSD notice?

The first 24 hours

Keep the lab report, do not drain or dose the system, isolate the tower only as advised, and call a specialist contractor. Then: an emergency decontamination visit, a laboratory re-test, and documentation for the file.

1. Keep the lab report — note the sample date, the sample point and the count. If a notice was served, keep the notice with it.
2. Do not drain or dose the system before taking advice. Acting first can destroy evidence and make the re-test harder to interpret.
3. Isolate only as advised — if the EMSD or your specialist tells you to shut down or isolate the tower, do it and write down the time.
4. Call a specialist contractor — call (852) 5923 7263 with the report in front of you. We will tell you what the result means and how fast the work must move.
5. Emergency decontamination visit — cleaning, desludging and disinfection to the EMSD Code of Practice.
6. Re-test — a laboratory sample that demonstrates the count has come down. Without it the notice cannot be closed.
7. Document everything for the file — the report, the notice, what was done and when, and the re-test result. Cooling tower records must be kept for two years.

What actually happens next

1. We talk it through — the result, the system, and whether a notice has been served. This tells us how fast we have to move.
2. We attend site and inspect the tower, the basin, the fill and the dosing equipment. A high count almost always has a physical cause: sludge, biofilm, a failed doser, or a pH problem.
3. Emergency decontamination — cleaning, desludging and disinfection to the EMSD Code of Practice.
4. Re-test — a laboratory sample that shows the count has come down. Without this you cannot close the notice.
5. Documentation — a dated report of what was found, what was done and what the re-test showed. This is the part that satisfies the EMSD and protects you.
6. Fix the cause — otherwise it comes back. Usually that means a proper ongoing programme rather than a one-off clean.

Why the count went high

In our experience it is rarely “no biocide”. It is more often one of these:

• Biofilm and sludge shielding the organism from the biocide that is present. See Legionella in water systems.
• pH drift — chlorine at pH 9 is roughly 95% in its weak, near-useless form. The residual looks fine; the kill is not there. See effects of pH on various biocides.
• Dosing equipment failure that nobody noticed between visits — the argument for continuous monitoring.
• Stagnation — a tower idle in warm weather, then restarted. See restarting a cooling tower after shutdown or typhoon.

If you have been served a notice

Since 2011 the EMSD has been able to enter premises and sample fresh water cooling towers at random. A total Legionella count at or above 1,000 cfu/mL triggers a statutory nuisance notice requiring emergency decontamination with re-testing. Non-compliance is an offence.

The responsibility sits with the building owner and duty holder — hiring a contractor does not transfer it. What closes a notice is properly executed work plus documents that prove it. See compliance.

Frequently asked questions