Risk assessing cooling towers for Legionella
How to risk assess a cooling tower for Legionella: the findings that should worry you, what each one points to, and how to rank the fix before you leave site.
Cooling towers & evaporative condensers
The system that drives the largest community Legionella outbreaks, and the one with the most demanding control regime under HSG274 Part 1. Everything from the water chemistry to the legal notification, in one place.
Key facts
- Notifiable to the local authority (1992 Regulations)
- CFU/L action levels (HSG274 Pt 1)
- HSG274 Part 1 is the governing guidance
- If a tower loses control
The cooling-tower articles
Case study: outbreak caused by a poorly maintained cooling tower
How a neglected cooling tower becomes a community Legionnaires' outbreak: missed dosing, dead drift eliminators, unread reports, and what to check first.
Cooling towers and evaporative condensers: high-risk systems
Cooling towers are the only Legionella system that can reach the public. Where the money goes, the duty to notify the council, and when to retire the tower.
Cooling tower notification duties and local authority registers
Notify your local authority about a cooling tower or evaporative condenser: what counts, what the register is for, and the evidence to keep on file.
Does air conditioning cause Legionnaires' disease? Split units vs cooling towers
Your office split unit almost certainly cannot give you Legionnaires' disease. The cooling tower on the roof is a different story.
HSG274 Part 1 explained: controlling Legionella in cooling towers and evaporative condensers
Cooling towers are the highest-risk Legionella systems on any site. What HSG274 Part 1 expects you to control, the notification duty, and how to evidence it.
Portable and evaporative air coolers: the heatwave Legionella risk that isn't a cooling tower
A portable evaporative cooler's tank can grow Legionella when left warm and stagnant. Here's why it isn't a cooling tower, and how to empty and dry it safely.
Cooling tower logbook and inspection checklist: what to record and how often
The cooling tower records a water logbook never covers: biocide dosing, dip-slide counts, drift-eliminator checks and clean dates, and how often to log each.
Cooling tower biocide programmes explained: oxidising vs non-oxidising biocides and dosing control
What a cooling tower biocide programme really does: an oxidising biocide under ORP control, rotated non-oxidisers and a biodispersant, proven by dip slides.
Cycles of concentration explained: cooling tower water chemistry, bleed-off and why it matters for Legionella
What cycles of concentration, conductivity, bleed-off and inhibitors actually mean on a cooling tower report, and how the chemistry feeds your Legionella risk.
Drift eliminators: the cooling tower component that decides who breathes the aerosol
What cooling tower drift eliminators do, why a damaged or missing one turns a tower into a public-health emitter, and exactly what to inspect and record.
Pre-commission cleaning and disinfection of cooling towers: when it is required and what good looks like
When a cooling tower must be cleaned and disinfected, how fouling drives the schedule, and the certificate and records that prove the work.
Cooling tower winterisation, shutdown and safe restart: managing a tower that goes idle
How to handle a cooling tower that goes idle: the three layup choices, why a stagnant tower breeds Legionella, and the clean-and-disinfect before restart
Who actually controls the cooling tower: the responsible person and water-treatment contractor split
You can outsource cooling-tower water treatment but not the legal duty. See exactly what stays with the responsible person and what the contractor actually owns.
A worked cooling tower control scheme: parameters, frequencies and action levels on one page
See a realistic evaporative cooling tower scheme of control: every parameter, target range, frequency and action level on one page to sense-check your own
Cooling tower Legionella sampling: frequency, action levels and what to do at each result
What to do when a cooling tower Legionella count lands at each action level, how often to sample, and when a result means your system has lost control
Cite this page
"Cooling towers & evaporative condensers: the complete guide." Legionella.io. https://legionella.io/cooling-towers/
Free to reuse under CC BY 4.0: quote, adapt or republish with attribution and a link back to the original.