All about ORP / Redox

ORP measurement (also called REDOX) is used to monitor water disinfection quality. The higher the concentration of ORP in water, the greater its capacity to eliminate harmful micro-organisms. The better the water quality for your health. ORP has become a regulatory standard in many countries. It is more reliable than measuring chlorine levels. This article explains what ORP is. Why it's the most effective way of determining the disinfection capacity of your pool / spa water

Why measure the ORP?

ORP (Oxydo Reduction Potential) is an indicator of the level of disinfection of your pool or spa water. An ORP probe, notably present in vour ICO connected probe, measures the electrical potential delivered by all disinfectant chemical agents. It is expressed in milivolts. Knowing the concentration level of disinfecting agents in water allows :

• To reduce disinfectant consumption in the case of dosing treatments.
• To optimize chlorine production in the case of an electrolyzer, thus limiting excess chlorine.

How to get a balanced ORP

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

Variation factors of the ORP

It is, however, normal to observe variations in your ORP measurements, as the latter vary according to UV and, above all, the pH of the water. If your measurements vary by +/- 50mV during the day in high season, there's no need to take any action. Simply check your pH and water temperature parameters regularly.

pH impact REDOX/ ORP measurement

In a chlorine pool, the higher the pH, the less effective the chlorine. Water disinfection - the ORP in this case - is consequently low. To summarize, the first thing to do when you notice a low ORP is to test the pH of your pool water. If the pH is above 7.6, then the pH is outside the optimum range (between 7,2 and 7.6). You'll need to lower the pH.

In a bromine or salt pool, it's the opposite of a chlorine pool. The higher the pH, the more effective and disinfectant the bromine. That's why the optimum pH threshold is higher: 7.2 and 7,6. If you have a bromine pool and your pH is low (below 7.4), this may explain why your ORP reading is too low. You'll need to increase pH level.

What to do when the ORP is too low?

Below 650mV, the water is not sufficiently disinfectant. Il there is a significant risk of bacterial proliferation in the water and the appearance of algae. Swimming is therefore strongly discouraged. In addition, a low REDOX/ORP reading can lead to green pool water. .

You have just filled your swimming pool or spa

It's normal to have a low disinfection level if you've just filled your pool.

The ORP has been low for a few days

Check the pH

• If your pool is treated with chlorine, check the pH
  • if the pH > 7.6 it is necessary to lower the pH in your pool
  • if the pH is < 7, the pool lacks disinfectant. It is necessary to add chlorine

• If your pool is treated with bromine or salt, check the pH
  • if the pH < 7.2 it is important to raise the pH in your pool
  • if the pH is between 7.6 and 7.8, your pool is lacking disinfectant. You need to add bromine

What should I do if the ORP is too high?

Above 750mV, chlorine becomes aggressive to the eyes and skin. This causes feelings of tightness and irritation. What's more, it can damage your equipment and bleach your pool or spa lining. We therefore advise against swimming.

Check the pH

As when the ORP is too low, you need to check the pH of your pool/spa water.

If you are using a chlorine treatment, and the pH < 7, you will need to add pH+.

For bromine treatments, if the pH is > 7.8, the pH should be lowered with pH-.

If the pH of the water is optimal, the solution to your ORP problem may lie with the stabilizer.

Check the stabiliser level

To measure the level of stabilizer in your pool, you need to use suitable strips. Here's how to interpret the results of your colorimetric test:

• Result 0-30 ppm the pool/SPA does not have enough stabiliser, the REDOX drops very quickly when chlorine is added. You need to increase the stabiliser level to achieve perfect disinfection.
• 30-50 ppm measure: ideal rate for pool/ SPA

• 50-60 ppm measure : the level is high but still acceptable. You can simply change your disinfection method by using non-stabilised chlorine.
• 60 ppm measure : The level is very high, you can drain part of the volume of water in the pool or SPA (by changing half the water, you will halve the stabiliser level) OR use a stabiliser reducer.

The ORP reading may rise sharply if

• You have just undergone a chemical treatment: in this case, starting the filtration should regulate the ORP within the next few hours.
• Your filter and filtration system are not clean
• Your ORP probe has not been recently calibrated (please refer to the manufacturer's operating instructions).

Why ORP measurement is more effective than chlorine measurement ?

To understand the difference between measuring chlorine and ORP, we need to distinguish between disinfected and disinfectant water:

A sanitized water (chlorine measurement): we measure the QUANTITY of total chlorine present in the water. This is water that has been cleaned of potentially harmful organic matter. When water contains sufficient chlorine, it is disinfected at the moment of measurement. But this does not last! A change in temperature or pH is all it takes for water quality to deteriorate rapidly.

A sanitizing water (ORP measurement): in contrast, the ORP measurement refers to the QUALITY of the sanitizing agents present in the water. Here, we measure active (or effective) chlorine. Depending on the quantity of disinfectant available in the water, it will always be disinfected in 3 hours, 2 days or 2 weeks. It is therefore more relevant to know this value rather than the amount of total chlorine present in the water.

Why choose a smart water analyser with an ORP probe?

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

1. Reliable measurements: your ICO's sensors are immersed at the right depth in the water. Every hour, the device takes measurements at several points in the pool for even greater reliability. The combination of several analyses enables our sensor to make a precise diagnosis of water quality and make the right recommendation.
2. Analysis and treatment recommendations: our connected sensor doesn't just analyze your water. It also sends chemical treatment recommendations to your smartphone, along with the product and dosage to use. These recommendations are customized according to whether you are using tablets, liquid,...
3. More sustainable and economical : Connected sensors last several seasons and are recyclable.While the purchase of a connected probe is more expensive than strips, personalized treatment recommendations will save you the use of chemicals every year. It's a greener solution! Finally, with ICO you have a connected probe that measures all the important parameters for keeping your water balanced.
4. Smart features: the ICO application lets you use various functions. The share function, the water index, and many more! Découvrez toutes ICO Spa main features .

To conclude

ORP-REDOX provides direct information on disinfection quality , unlike chlorine concentration. Chlorine measurement with strips measures the total amount of chlorine present in the water. Although all forms of chlorine participate in disinfection (active, potential and chloramines), some disinfect much less than others. This is why ORP measurement is the most effective way to monitor the quality of your pond water.