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Don’t Make These 3 Cooling Tower Mistakes

Nearly one year after our first legionella seminar we’ve got some more concrete details to share with you. We had a client this year who actually had a few back-to-back legionella spikes. We were of course really disturbed that we let a client get into that situation. Rather than hide it and pretend it never happened we thought that we’d share what we learned.

Here are 3 mistakes we let our client make.

Dosing Failures Going Unnoticed

At the first failed Legionella test (tests are legally mandated on a monthly basis here in Quebec), the client called us in, as per protocol, to evaluate the situation, identify the possible causes and help them get the system back under control. Our team noted a few things, one of which was that the chemical dosing system had not been functioning properly. After some analysis it was determined that a mix of equipment failure and user error were to blame.

The problem is that this kind of failure should never go unnoticed. Anybody operating a cooling tower should be checking the functionality of these systems daily. So where did things go wrong?

This particular treatment contract didn’t include regular service visits. We offered the client a flexible, “on call” service arrangement where they could decide to call us in when they needed a hand. We should have made a better read of the situation and insisted on regular monthly visits for the first few months in operation. We should have made sure to be more present for in-depth training.

Low Frequency Bacteria Testing

Despite our explanations before and after signing the service contract, the client didn’t understand the reason for doing frequent bacteria testing. In their case, we had specified they should be using dip slides at the very least once a week to make sure bacteria wasn’t growing out of control in their tower network.

Once we finally got them testing on a more regular basis we were able to see that things were still not under control despite having gone through two shock treatments and a full physical tower cleaning. This pointed to biofilm development throughout their relatively small network.

dip slides
Dip slides taken at 1-week intervals

Once again we fell down on the job by not making sure the client really got it when we explained they should be doing regular bacteria testing on their systems. Doing legionella testing once a month is like driving down the highway and only opening your eyes every hour. You won’t know things are going horribly wrong until they already have.

Not Addressing Biofilm

In an ideal world biofilm doesn’t build up because biocides prevent the bugs from ever getting that far. In reality, that doesn’t always work. In this case, there was almost no way it could work, knowing what we know now.

Right from the start the client’s system was contaminated: their pipes were covered in biofilm. We were slow on the uptake noticing this one. Once again, we really should have insisted on being there more often in the beginning. Anyway, enough self-flagellation. What should we have done?

Simple. We should have made sure the client had cleaned his network with an appropriate mix of biocides and bio-dispersants before getting up and running at the beginning of the season. Then, we should have equipped the client with the training needed to keep things under control going forward.


For lots of you cooling tower season is just getting started. We hope this article helps you take a few points into consideration. If you’d like some help making sure you get your cooling tower started up right, just give us a call and we’ll be happy to get it right.

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