Over the last couple years, there has been much talk about the need for parts-per-million (ppm) chlorine monitoring, with several chemical controller companies developing ppm technology. Some have even suggested the new California Title 22 mandates ppm monitoring and recording.
But there is good reason why the industry has and probably will continue to use Oxidation Reduction Potential (ORP) as the standard for chlorine control, even though ppm sensors, using both amperometric and DpD measurement devices, have been around for decades.
There also is good reason to measure ppm. Most county health agencies require, measure and evaluate water disinfection based on the chlorine’s ppm. This is also what most industry test kits provide for us with colorimetric, titrimetric and electronic testing.