Home Email Sales Info Technical Support Product List

What is ORP?

ORP (also known as Redox) is a measurement in millivolts (mV) of the Oxidation-Reduction Potential produced by an oxidizing sanitizer in water. It provides a superior index of bacteriological water quality because it monitors the activity of the sanitizer rather than just its relative concentration as with conventional PPM (parts per million) test kits.

In 1971, the third edition of the "International Standards for Drinking Water Quality" of the WORLD HEALTH ORGANIZATION (WHO) stated:

"A redox potential of 650 mV (measured between platinum and calomel electrodes) will cause almost instantaneous inactivation of even high concentrations of virus. Such a potential can be obtained with even a low concentration of free chlorine but only with an extremely high concentration of combined chlorine."

For the current position on ORP of WHO - or lack thereof - see their website at:

In 1985, a study of thirty commercial spas by the Oregon Health Department also confirmed 650 mV to be the minimum value required to prevent the growth of germs and bacteria. An ORP level of 750 mV is recommended for public pools and spas.

All CHEMTROL® controllers use a high quality, reliable ORP sensor featuring a high-purity, solid Platinum band, not a thin coating or a thin rod.

What is HRR?

HRR - standing for High Resolution Redox - is just a marketing name used by a competitor to promote their ORP sensors.

Following is an analysis report by Robert J. Garrahy of BROADLEY-JAMES CORP., a respected manufacturer of electrodes in California.

"As you know, we purchased an "HRR" ORP sensor and took it apart to analyze its components.  The construction of the sensor was very traditional and the workmanship was average for an inexpensive disposable electrode.  The sensing tip was unique since it was not pure Platinum but rather a thin coating of Platinum over a Titanium substrate.  The coating was very pure but differs by only a few thousands of one percent from a standard Platinum band design and that band is solid Platinum not a coating.  This little added impurity does nothing to improve the performance of the sensor.

In summary, the electrode is the same as any other, but adjectives used by the company to describe it are quite plentiful.  Any arguments put forth were unsupported or circular.  It's safe to say that you will not find the terms "HRR" or "High Resolution Redox" in any scientific peer reviewed journal, it will only appear in advertisement or promotional articles. "High Resolution Redox" is the same as saying "NEW IMPROVED Tide" or "Quaker 100% NATURAL"...... it's a brand name and not a technical definition."

It should also be noted that the use of a thin coating of Platinum tends to reduce the useful lifetime of the sensor because the coating is more easily abraded than the solid Platinum ring used in CHEMTROL® sensors.

Go to Top