Why Your Dosing System's ORP Reading Is Not Enough: The Free Chlorine Testing Requirement in Victoria

One of the most common compliance gaps we find when auditing Melbourne's commercial pool facilities is this: the operator is relying entirely on their dosing system's ORP (Oxidation Reduction Potential) reading as their chlorine measurement. Under Victorian regulations, this is not sufficient.

WHAT IS ORP?

ORP measures the oxidising power of the water — the ability of chlorine to sanitise. It is a useful indicator, and automated dosing systems like the Prominent Dulconex and Chemtrol PC155 use it to regulate chemical dosing. However, ORP is an indirect measurement. It is influenced by cyanuric acid levels, pH, temperature, combined chlorine, and total dissolved solids — which means a high ORP reading does not always mean your free chlorine is within the required range.

WHAT VICTORIAN REGULATIONS ACTUALLY REQUIRE

Under the DHHS Water Quality Guidelines for Public Aquatic Facilities 2020 and the Public Health and Wellbeing Regulations 2019, facility operators are required to measure and record DIRECT free chlorine levels — not just ORP. This means a DPD-based test (using a photometer or comparator kit) must be performed at the operational monitoring frequencies specified in your WQRMP.

THE PRACTICAL IMPLICATION

If your facility has an automated dosing controller and your technician or caretaker is simply reading the ORP value off the controller panel without performing a direct free chlorine test, you are non-compliant with your monitoring obligations — regardless of how good your dosing system is.

THE SOLUTION

A properly set up compliance programme will use your automated dosing system for continuous control AND supplement it with direct free chlorine testing at the intervals required by your WQRMP. At Ace Aquatics, we set up facilities with both layers: automated dosing for precision, and documented manual testing for regulatory compliance.

Need to review your monitoring programme? Contact Ace Aquatics: 0422 470 214 or aceaquatics.com.au/contact