Cooling towers, spas, condensers and a variety of other tools all typically require regular inspection in order to ensure that they are working safely. One of the cornerstones of these inspections is the detection of Legionella, which many building owners and operators are likely already familiar with.
However, one lesser-known but important metric of ensuring that water is safe is HPC measurement. It is important to understand how metrics established by HPC can benefit your building but also learn what HPC is not able to determine.
What Is HPC?
HPC is a shortened form of Heterotrophic Plate Count, which is a type of testing that can be done to locate and ascertain the number and type of certain live bacteria in water. A Dipslide sometimes may be referred to as a HPC test, however HPC is actually a laboratory test.
This is valuable for a number of reasons, from determining the state of a building’s water quality to making plans to eliminate specific strains using targeted water treatment to keep the facility’s water system safe and clean. However, HPC is not foolproof, and it must be used wisely.
How Is It Related To Legionella?
One of the most common misconceptions when learning about HPC is to immediately begin to use it as the primary method of determining whether a system contains Legionella or not, since Legionella is a heterotrophic bacteria.
After all, Legionella is one of the most dangerous bacteria that most building operators and managers need to worry about, because it can cause severe illness and even death in humans. Cooling towers are a particular risk since they dispel water vapor into the air around a building due to their regular evaporation during operation.
Can HPC Tests Work On Legionella As Well?
Unfortunately, no true link has been established between HPC testing levels and Legionella levels within a particular sample.
High HPC could mean your system has an elevated level of Legionella. However, there is no proof that this could be the case. HPC is the measurement of total bacteria that can live in the presence of oxygen and Legionella is only one such bacteria.
There may be many reasons for the lack of consistency in HPC tests when it comes to Legionella. One theory is that Legionella are able to quickly regrow if their numbers are low; thus, a low HPC count during a test does not indicate that Legionella is not present, after which it may proliferate extremely quickly.
Another conjecture is that other types of bacteria can outcompete Legionella; in this scenario, the results of an HPC test may be high, indicating a dense presence of heterotrophic bacteria, but colonies may not include Legionella. Since neither a low nor a high result conclusively proves the presence or absence of Legionella, HPC is not sufficient as a testing method.
How HPC Testing Fits In
If HPC testing does not reveal the presence of Legionella, then what purpose does it serve? While you will need to tackle your Legionella sampling in a different manner—which is often explained in detail by your local and state regulations—HPC testing can still prove to be a valuable tool.
It is better at locating, for example, clusters of non-tuberculous Mycobacteria and other microorganisms that can still threaten the cleanliness and safety of your water. With this information, you can begin to develop a strategy for specific, targeted water treatment, whether that comes in the form of chemicals, biocides or another choice that is right for you.
Another valuable insight to be gained from HPC testing is the overall efficiency and function of your already existing filtration and treatment systems. If you observe a gradual increase in HPC results over time, it is worth considering that your methods may no longer be working as effectively or that some part of your system’s equipment may be compromised.
However, remember that Legionella testing is a separate endeavor that will need to be performed with its own unique methods to determine whether colonies are forming in your water. If you need assistance with the various types of water testing, the simplest solution is to reach out to an expert with experience.
Work With The Legionella Prevention And Treatment Professionals
Whether you would like to use HPC testing to get a better idea of the state of your water or you need assistance with testing for Legionella now that you know that HPC testing is not sufficient, a skilled water treatment professional can help.
The experts at Legionella Compliance Solutions would be happy to help you determine the safety and composition of your water so that you can make informed decisions. Reach out to schedule an appointment with our experts to meet with a professional and establish a safe and effective strategy for managing your water.