You may be asking yourself “I have a water treatment plan in place, why do I need to clean my Tower?” There are multiple reasons to perform annual, or semi-annual tower cleanings. The first being it is mandated by law in some states to maintain compliance. New York State has made an annual physical tower cleaning mandatory with the regulations adopted in August 2015.
Besides legal compliance, another reason is to maintain system efficiency. As a cooling tower operates, wind-blown dirt and debris can deposit into the basin of the cooling tower. As the debris settles, it creates a shelter for microbiological organisms. Once this occurs, the biocide cannot reach these organisms, and a corrosion cell then forms. This debris can also begin to clog heat exchangers, strainers etc. When this occurs heat transfer ability does drop resulting in increased power usage to run fans, chillers etc. It can also cause premature failure to piping and the tower itself through microbiological induced corrosion.
The other reason, which is the most important, is for public health. The regulations put forth by New York was in direct response to a Legionella outbreak within New York City. As stated above, debris and bio-film can prevent a biocide from doing its job and reducing the risk of bacteria becoming airborne in the water vapor.
These are just a few reasons why the industry best practice and OSHA and ASHRAE 188 standard is semi-annual cleanings.