Aquarius Technologies: Why FAC-Controlled Systems Are Superior
Multiple studies, including the 2018 Northern Sydney Public Health Unit investigation published by Environmental Health Australia (Queensland), have shown major limitations in using Oxidation Reduction Potential (ORP) alone for pool disinfection control.
The study found wide variability in ORP readings across pools, even when pH and Free Available Chlorine (FAC) levels were within acceptable ranges. Some pools with compliant ORP readings had inadequate chlorine residuals, while others with low ORP values maintained safe disinfectant levels. The report concluded that “ORP as measured by pool operators cannot be relied upon to ensure a suitable FAC level after adjusting for pH” (EHAQ, 2018).
This inconsistency occurs because ORP measures only the oxidation potential of water, not the actual disinfectant concentration. ORP readings are easily influenced by pH, temperature, cyanuric acid, probe calibration, and other oxidisable substances. As a result, two pools with identical ORP values may have very different chlorine concentrations and sanitation effectiveness. Subsequent studies in Minnesota and Europe confirmed that ORP readings vary significantly under different chemical and environmental conditions, making it difficult to apply a universal standard.
In contrast, FAC-controlled systems directly measure the true concentration of free chlorine (mg/L), the most accurate indicator of microbial inactivation and compliance. By providing real-time chlorine data, FAC control eliminates the uncertainty of ORP-based interpretation and allows for faster, more precise chemical dosing. This ensures stable disinfectant levels that meet public health regulations and effectively inactivate pathogens. Reflecting this, New South Wales removed ORP as an accepted compliance method in its Public Health Regulation 2022, highlighting a shift toward direct residual chlorine monitoring.
While ORP can still be useful for observing oxidation trends, FAC control provides the accuracy, reliability, and compliance confidence required for modern aquatic facilities. It allows operators to maintain consistent water quality and minimise the risk of illness outbreaks, closures, and legal exposure.
Cryptosporidiosis and Public Health
Recent cryptosporidiosis outbreaks have emphasised the importance of accurate disinfection control. In 2024, Victoria recorded 2,349 cases (a 233% increase), while Western Australia saw 800 cases—a 300% rise. This chlorine-resistant parasite spread through contaminated public pools, prompting closures such as Melbourne’s Northcote Aquatic Centre. Health authorities advised people not to swim for two weeks after diarrhoea symptoms to prevent further transmission.
Legal and Liability Considerations
Although no class actions have yet occurred for cryptosporidiosis, public liability claims for pool-related illnesses are common. Operators—including councils, hotels, and resorts—can face claims for negligence, such as poor maintenance, unsafe water conditions, or chemical mismanagement. Victims may seek compensation for medical costs, pain, and lost income, reinforcing the need for accurate, compliant disinfection systems like FAC control to ensure safety and limit liability.
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