5. Understanding ORP: Oxidation Reduction Potential
December 2, 2016 /by Orenda Technologies
Have you ever been asked "what is ORP?" For most of us, we kind of know what it represents, but not exactly what it is, or why it is important. Oxidation Reduction Potential (ORP) is a measurement of sanitizer effectiveness in water. ORP is an electronic measurement–in millivolts (mV)–of the ability of a chemical substance to oxidize or reduce another chemical substance. Both oxidation and reduction are chemical processes involving the transfer of electrons between molecules (gaining or losing an electron).
So ORP measures the potential for such reactions to occur in your water. Translated into the swimming pool world, the higher the potential for oxidation, the more efficient your sanitizer. More efficient sanitizer means safer, cleaner water. ORP is measured by a probe in a small sample of flowing water, usually next to a chemical controller. An ORP sensor consists of an ORP electrode, and a reference electrode. A signal is sent between them which determines the oxidation and reduction potential. The rate of electron transfer is measured in mV and read as ORP. The higher, the better, and most health departments in the United States recognize -650mV as the minimum acceptable ORP. Anything over -850mV is exceptional water.
Oxidation and Reduction are two different things; in fact, they are opposites. We get the following two definitions from this source.
Understanding ORP, and why it is used
ORP is widely used because it is practical, usually accurate, and allows us to electronically monitor what is going on in the water. While it does not measure the amount of chlorine, ORP is a real-time reading of chlorine's performance. Most operators agree that disinfection is what really matters, from a health perspective; the amount of chlorine is not necessarily as important as its effectiveness. Ideally, we would have a minimal amount of chlorine that is super efficient, to accomplish more with less.
We did some research, and we have not yet found data that suggests an ORP that is “too high”, or where it starts becoming less valuable. What we do know is that ORP should be above -650mV; anything over -750 is good; and anything over -800 is excellent.
Beyond that, the exact numbers are subject to operator opinions, but we can all agree that higher is better.
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