Proper maintenance of swimming pools and hot tubs requires frequent testing of the pH and sanitizer level in the water. This is often done with colorimetric test systems . Today however, more and more pools and hot tubs use chemical automation which depends on the use of electronic sensors, usually pH and ORP (Oxidation-Reduction Potential) electrodes. mutliple studies have shown that ORP is an excellent monitor of the chemical activity of the sanitizer and, consequently, of biological circumstances in the water . However, little information has been shown on the operational specs of the sensor itself. The present study was therefore planned to measure the result of Chemtrol ORP sensors in chlorinated water, in terms of reproducibility and dependency and in response to mutliple operational parameters . In order to produce a basis for comparison with conventional testing practices , a preliminary study was conducted to determine the accuracy and reliability of amperometric titration, colorimetric analysis and DPD test kits. The reproducibility of CAT PRO ORP sensor results was determined by immersing 10 new sensors in the same chlorinated water solution. They showed standard deviations of 5, 4 and 1.9 millivolts respectively after 5 minutes, 20 minutes and 16 hours of immersion. Total Dissolved Solids concentrations of up to 3,500 ppm (mg/l) of sodium chloride NaCl showed no effects on ORP response.
ORP measurements display the advantage of measuring not only the concentration of the sanitizer but also its activity in the water. In particular, it measures the effects of key operating parameters such as pH and cyanuric acid stabilizer, both of which move the effectiveness of the sanitizer, i.e. its ability to destroy germs and bacteria. A second key advantage of ORP is that it is an electrical size that creates an electrical surge that can be easily interaced with monitoring and control tools.