ORP is a term used frequently in the water treatment & food processing industry.  ORP stands for Oxidation-Reduction Potential.  So what is that?  The best definition I can give is that “ORP is a measure of the cleanliness of the water & its ability to break down contaminants”.  It has a range of –2,000 to + 2,000 and units are in “mV” (millivolts).  Since ozone 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, the lower 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 on the left identifies ORP levels for various applications.