A cooling tower is the highest risk device in this subject. It moves large volumes of warm water through the open air and creates drift, which is exactly the aerosol that carries the bacteria, and it can affect people who never enter the building. That is why cooling towers carry duties that hot and cold water systems do not, starting with telling the local authority they exist.
Notification, which is separate from the risk assessment
Cooling towers and evaporative condensers must be notified to the local authority under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992. The notification names the premises and the device, and it has to be updated when the device is taken out of use. It exists so that when a cluster of cases appears in an area, the authority already knows where to look.
What routine control looks like
Continuous or dosed biocide treatment with the levels monitored and recorded, because temperature control is not available on a device designed to cool water. Regular inspection of the pack, the pond and the drift eliminators. Cleaning and disinfection on a defined schedule. And routine legionella sampling, which for cooling towers is genuinely part of the regime rather than the exception it is for domestic systems.
Where side stream filtration comes in
A side stream filter continuously draws a proportion of the circulating water, removes suspended solids and returns it. Solids feed biofilm and shield bacteria from biocide, so removing them makes the chemical treatment work better and reduces how often the tower has to be cleaned. It is a supporting control rather than a replacement for treatment or monitoring.
Why the duty reaches further than the site boundary
Section 3 of the Health and Safety at Work etc. Act 1974 covers people who are not your employees, and cooling tower outbreaks have reached people walking past. That is the reason the enforcement interest in towers is disproportionate to their number, and the reason a tower nobody has looked at for a year is the single most serious finding in this subject.
Questions people ask about cooling tower maintenance
Do cooling towers have to be registered?
Yes. Cooling towers and evaporative condensers must be notified to the local authority under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992.
Is legionella sampling required on a cooling tower?
Routine sampling is part of the normal regime for cooling towers, unlike domestic hot and cold water systems where HSE states it is not usually required.
What is side stream filtration?
Continuous filtration of a proportion of the circulating water to remove suspended solids, which improves biocide performance and reduces fouling. It supports the treatment regime rather than replacing it.
Who is responsible for a cooling tower?
The duty-holder in control of the premises. The duty extends to people who are not employees, including members of the public near the site.