Take Your ORP to PPM Conversion Chart and Throw It Away!

As a chemical automation manufacturer, we get calls saying there is something wrong with the controller because the ORP/PPM relationship on a typical conversion chart doesn’t agree with what the controller is saying. The charts are derived from laboratory data which has no relation to real world situations such as combined chlorine, cyanuric acid levels, nitrates, phosphates and other variables. The biggest influencer of ORP will be cyanuric acid or conditioner. The more there is on the water, the greater the effect on lowering ORP.

Orp is a qualitative measurement while PPM is a quantitative measurement. The key to using an ORP/pH controller is to find an orp value based on required ppm & pH levels and use that as a set point. Having an ORP in the range of 700-800 will give you good water quality.