The SafeDip’s chlorine reading is the measurement based on the ORP chemistry reading. ORP stands for Oxidation Reduction Potential.
ORP measures how effective the sanitizer is in your pool or spa water. The ORP measurement ranges on the SafeDip are between 500mV to 800mV.
The North American standard for the optimal ORP range in your pool or spa water is between 650 – 750mV. The SafeDip does not show the actual level of chlorine your pool water has, but how effective the chlorine is in the water based on the oxidation-reduction potential. With this understanding the SafeDip will provide you the chlorine readings as follows:
Low: if the ORP reading is below 650mV
Good: if the ORP reading is between 650 – 750mV
High: if the ORP reading is 750 – 800mV
The ORP reading is a better gauge on how sanitary a sample of water is as opposed to just measuring free chlorine. There are scenarios where you have the right amount of free chlorine but still have a cloudy or green pool or spa. Certain chemical levels in the water like improper pH, Total Alkalinity, and stabilizer levels, as well as phosphate/nitrate levels above 0ppm, in the water effect the chlorine. The SafeDip shows "Low" on chlorine level because of the improper chemical levels, indicating something in the water is preventing your sanitizer from doing its intended job. It does not mean the pool water has a low amount of chlorine, but how little the effectiveness of the free chlorine in the water.