• 04.05.2020
  • WTW | Lab Segment

ORP in swimming pools

ORP in swimming pools

In the monitoring of swimming pools by technical staff, health authorities and associated labs, the ORP (Redox) is a very important parameter alongside chlorine and pH. It’s little wonder then that training courses at the NORDUM Academy highlight the testing of pool water for the cross reaction of pH, chlorine and the redox potential (measured in mV).

These are essential parameters when trying to reach an optimal condition of pool water. According to many national regulations, the redox potential is a mandatory checking parameter: The ORP value characterises the disinfecting activity of the added chlorine and thus the accomplishment of regulations; in Germany e.g. the fulfilment of infection protection law §37 Abs.2.

The optimal ORP value for the fastest and most effective germ-killing is 750-770 mV. The ORP value is dependent on the presence of different chlorine compound concentrations, which in turn are correlating with the pH value of the pool water. A pH between 6.5 and 7.6 shifts the equilibrium in favour of the hypochloric acid, which has a strong disinfecting effect. Both, pH and ORP are temperature-dependent parameters. A correct temperature compensation of the pH and ORP measurement is essential for correct measuring and finally correct chlorine dosing.

In seminars of the NORDUM Academy the correlation of parameters as well as hands-on training for sampling and measurement of pool water with the relevant parameters are deepened in collaboration with our product specialists:

The portable colorimeter pHotoFlex® pH provide the use of an electrochemical pH and an ORP sensor (one after the other) with Automatic Temperature Compensation (ATC) – comparably to WTW® electrochemical instruments. In combination with the full range of photometric test kits for water quality measurement like chlorine, they guarantee the reliable day-to-day monitoring and high-level surveillance of health administration with documentation and AQA at the same time.

To add turbidity measurement as an indicating parameter for microbiological contamination, photoFlex® Turb offers the same valid testing range together with an IR-LED fulfilling DIN EN ISO turbidity measurement on top.

Find more information on the product pages of the photoFlex® pH and pHotoFlex® Turb.

Image credit: Mrs. Dr. Holz (NORDUM Akademy) and Mrs. Holst (Xylem Analytics) during training seminar in Rostock, Germany, September 2019