What is ORP?
ORP stands for Oxidation Reduction Potential or Redox. It is the activity or strength of
oxidizers and reducers in relation to their concentration in water. It is not (like pH) a
measurement of concentration, rather of activity level. Different meters are available to
measure the ORP in your water. ORP is measured in millivolts (mV) with no correction
In theory, the higher the ORP reading, the less potential for bacterial activity in the
water, and vice versa. ORP measurements are typically taken for drinking water, spas,
swimming pools, etc.
The ORP measurement went down after running my water through a Berkey®
system. Is this OK?
Actually, yes. The Black Berkey® purification elements at the heart of your Berkey®
system are capable of reducing a whole host of potential contaminants from your water,
starting with viruses and bacteria. In that these possible contaminants are already
removed from your purified water, the ORP measurement becomes irrelevant as
disinfection is no longer necessary in your post filtered water. While a higher ORP
would be desired for untreated water…this is simply not the case for water purified using
a Berkey® system.
Further, using meters available to measure ORP is not a perfect science. For example,
“…ORP relationships are not uniform for all oxidizing disinfectants…research has
shown that ORP is not a practical method for monitoring the antimicrobial potential of
water treated with hydrogen peroxide or peroxyacetic acid.” (1)
(1) If you would like to read more information on ORP, reference this document from the
University of California: http://anrcatalog.ucdavis.edu/pdf/8149.pdf
What is ORP?