ORP Measurement

ORP Basics

ORP is a term used frequently in the recreation water industry. ORP stands for "Oxidation-Reduction Potential." So what does that mean? A good working definition is that "ORP is a measure of the cleanliness of the water and its ability to break down contaminants." ORP has a range of -2,000 to +2,000, and units are in "mV" (millivolts). Since MINLOX™ is an oxidizer, we are only concerned with positive ORP levels (above 0 mV).

ORP sensors work by measuring the dissolved oxygen. More contaminants in the water result in less dissolved oxygen because the organics are consuming the oxygen and therefore lowering the ORP level. The higher the ORP level, the more ability the water has to destroy foreign contaminants such as microbes or carbon-based contaminants. The chart below identifies ORP values for various applications.

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Additional Information

ORP +300 mV and above: Oxidation of organic compounds like VOCs, hydrocarbons, elimination of taste and odor issues that are contributed by biological contaminants generated from algae and other naturally occurring sources. Geomins; 2-MIB; Extra-polymeric substances.

ORP +300 mV and above cont.: Oxidation of inorganic compounds. Breaks down disinfection byproducts and does not create new DBPs. Water systems that contain sulfuric acid, hydrogen sulfide, iron sulfide, sulfur dioxide, iron, manganese, ammonia, and mercaptans.

ORP +400 mV and above: Oxidation of pesticides; emerging recalcitrant contaminants; pharmaceuticals; antibiotics.

ORP +650 mV and above: Oxidative stress is incompatiblewith the biological functioning of most microorganisms. Very reactive, superior residual protection. Oxidizes EPS (extracellular polymeric substance).

ORP +700 mV and above: At this level of oxidative stresswater is considered potable.

*ORP Values were set by WHO (World Health Organization) back in the 1970s.

This is an ORP chart to use as a guideline when treating water.