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What Is Oxidation Reduction Potential (ORP)?

ORP, or Redox Potential, is a measurement of water’s ability to oxidize contaminants. The higher the ORP, the greater the number of oxidizing agents.


Checking ORP is a simple method to monitor the effectiveness of a sanitizer or the quantity of anti-oxidants in a liquid. In generalized terms for humans, a higher ORP is better for outside of the body, while a lower ORP is preferred for consumption due to the high anti-oxidant value.


There are numerous applications for ORP, each with its own specific optimum value. For example, the minimum ORP for pool & spa disinfection (set by the World Health Organization) is 650 mV. Though the WHO has not set a standard for ORP in drinking water, anything below -550mV is considered too strong and not recommended for drinking.


**HM Digital makes no health claims regarding ORP nor the use of ORP testing. It is the responsibility of the user to consult a professional in the applicable field for all safety and health concerns prior to the use of this meter.

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Did You Know?

Water is our planet's most precious resource.

  • The average American uses about 50 gallons (190 liters) of water daily.
  • Flushing a toilet uses 2 to 7 gallons (7.5 to 26.5 liters) of water.
  • A five-minute shower uses 25 to 50 gallons (95 to 190 liters) of water.
  • Leaving the water on while brushing your teeth wastes 2 gallons (7.5 liters) of water each time!
  • At least 400 million people live in regions with severe water shortages.
  • Water is the original health drink.  It contains no fat, no calories and no cholesterol.