Water cooling tower cleaning

Technicians perform a deep clean to remove Legionella risk.  All our technicians have food safety understanding and experience, which is paramount when it comes to this clean – the risk of contracting listeria and other pathogens is high.  Compliance cleans are also completed, to meet AS/NZS 3666.

What is a water cooling tower?

A water-cooling tower (WCT) is a specialized heat exchanger[1] that brings water in direct contact with air, to reduce the temperature of the water.  The heat recovered can be used in other factory processes, increasing energy efficiencies for the plant. 

Most food processing factories have cooling towers, especially as part of their plant. Normally they are used to cool water that is either going to be reused or is about to enter the wastewater system. 


diagram of how a water cooling tower works


Why do they need to be cleaned?

A cooling tower works by running air and water through fill. 

Hot water travels down, while cold air is pushed up through the water, cooling it. The minerals in the water, like calcium, build up on the fill – we call this ‘barnacles’.  These barnacles stop the water flowing down, and the air getting up, therefore they massively decrease the efficiency of the cooling tower.  Mineral build-up like this needs to be removed.  Sometimes it can be dislodged with pressure washing, otherwise we use an acid to soften it first.

Not everyone can clean cooling towers.  Many of our customers have unknowingly employed inexperienced contractors to clean their towers who have done a poor job.  Often, they will have used too much pressure and broken delicate parts of the system.  To best protect your assets, make sure your cleaning contractor understands and is experienced in water cooling tower cleaning. 


Why is it dangerous?

Legionella is a bacterium that thrives in wet environments, especially warm ones.  In a cooling tower, there are many warm, wet surfaces.  This is a perfect breeding ground for Legionella, therefore there is a risk of contracting Legionnaires’ disease when cleaning them.  Legionnaires’ disease is a severe pneumonia that can be fatal.[2] 

Water cooling tower cleaning can also be confined space entry.  This means you need trained technicians, and full job safety and area analysis plans and emergency recovery plans completed and signed on by all parties before work commences.


[1]  SPX Cooling Technologies: What is a Cooling Tower? 

[2] WorkSafe NZ: Preventing Legionnaires’ disease from cooling towers and evaporative condensers

How do we clean water cooling towers?

We have a unique standard operating procedure for cooling towers that includes a multi-stakeholder agreement.  This is the special requirements of every stakeholder – e.g the government, your factory, the tower manufacturer, the people who treat your water etc. – all put together into one process for our technicians to follow.  Our customers have found this extremely helpful and efficient as opposed to every stakeholder caring only about their individual needs that often conflict with those of other stakeholders. 

Our technicians work by a very detailed water-cooling tower standard operating procedure (SOP).  If you would like a copy of this SOP, please email info@prescogroup.co.nz

Here is a summary of the steps involved:

  1. Isolate the water supply and fans.
  2. Remove all drift eliminators
  3. Wash these with a very light wash. Drift eliminators are fragile, as they are often made from plastic. Even if they are metal, any rusting makes them fragile, so they still need to be soft washed. 
  4. Wash down inside the cooling tower to remove any plant life and scaling that we can reach from the pipes that run through the tower.
  5. Wash the exterior to get rid of any plant life.
  6. Go inside.
  7. If we can get to the pipes from inside, we pressure wash up to them as well. Wash any of the fills we can get to.  Usually there are more panels on the side, that you can open and clean more of the fill. 
  8. Get rid of any rubbish that has fallen into the tower.
  9. Rinse from the top again. This time it is not a pressure wash, but rather flushing volumes of water through the cooling tower.  Any of the soil that has been previously loosened is flushed into the basin.
  10. Suck the basin out with the vacuum truck.
  11. Pressure wash the inside of the units to remove any build-up or soil. This can be quite aggressive, as they are mainly metal. 
  12. Suck everything out with the vax truck again.
  13. Replace the drift eliminators at the top and fasten the straps. If the straps are broken, report to the site. 
  14. Final clean up around the area.


Why is our cooling tower cleaning process safe?

The cooling tower cleaning experience of our technicians is really important to us, and they have been mentored by a Water Treatment expert at our local dairy factory in Hawera.  Over the years, he has given them feedback on their methods, and taught them all the risks and tricks they know. 

If our technicians follow our SOP thoroughly, and wear all the correct PPE, this process is safe. 

The SOP embraces:

  • the WCT manufacturers maintenance recommendations,
  • ASNZS 3666.2 (check the number) Standards
  • Worksafe NZ guidelines
  • A Global Industrial Manufacturers internal standard for Legionella Control
  • Presco Environmental’s Integrated Management System policies and procedures.

To ensure they are competent to undertake this work, our technicians are qualified in:

  • Chemical handling
  • Confined Space Entry and Gas testing
  • First Aid
  • Safety Watch
  • Safe working at Heights
  • Hazard Identification and Control
  • Common Permit to Work system