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All about ORP / Redox

Disinfection of your pool or spa water is necessary to prevent the growth of unpleasant and unhealthy micro-organisms while swimming. Many tools can measure water disinfection, such as test strips, electronic testers and connected analysis solutions. However, they do not measure the same thing; here is everything you need to know about ORP and disinfection.

Definition of ORP

ORP (Oxydo Reduction Potential) also known as REDOX is an indicator of the level of disinfection of your pool or spa water. An ORP sensor, included in your ICO, measures the electrical potential delivered by all disinfecting chemicals. It is expressed in mV.

ORP is not specific to chlorine and this is its advantage over other technologies.


comprendre l'ORP : tableau différents type de chlore

What is the difference between chlorine concentration measurement and ORP measurement?

In most cases, the disinfectant used is effective chlorine. Let's look at the difference between measuring chlorine and measuring ORP.

The effective chlorine is composed of different elements:

  • Active chlorine:
  • Potential chlorine:
  • Chloramines

All forms of chlorine are involved in disinfection (active chlorine, potential chlorine and chloramines) but there are some that disinfect much less than others.

ORP-REDOX gives direct information on the quality of disinfection in contrast to the chlorine concentration, which measures the total amount of chlorine in ppm.

The ORP takes into account the contribution of each form of chlorine in disinfection.

However, effective chlorine is very sensitive and varies according to water conditions such as temperature and pH.

As mentioned in our article on the impact of heat, the effectiveness of chlorine decreases considerably above 28°C.

la chaleur impacte l'efficacité du chlore / mesure ORP

Changing from pH 7.4 to 7.8 reduces the amount of active chlorine by 22%.

la température impact l'efficacité du chlore / mesure ORP

To summarise:

By measuring the ORP, ICO gives you an overview of the disinfection quality of your pond water, unlike other analysis tools such as strips that measure the total effective chlorine or free effective chlorine .

For optimal disinfection of water at 25°C, international standards recommend ORP / Redox measurements between 650 and 750mV.