ORP value and redox

ORP Value | Meaning

You may be familiar with the terms ORP value and redox from swimming pools and spas. The name ORP is an English abbreviation for "Oxidation Reduction Potential". Redox is an amalgamation of "Reduction" and "Oxidation". The redox or ORP value is mainly used in swimming pools to indicate how pure the water is and to what extent it is able to break down impurities on its own. This is also known as the potential.

Is there a difference between the term ORP and Redox?

No, there is no difference between the terms ORP and Redox. Both terms are an abbreviation for the oxidation reduction potential.

ORP Value | Measurement

The ORP or Redox value measures the oxidising capacity of water and also gives a good indication of the concentration of dissolved oxygen. This value is measured in milliVolts (mV) and varies between -2000 mV and +2000 mV. The higher the value, the purer the water. With many impurities in the water, you can see that the concentration of dissolved oxygen is low. This is because the impurities consume the dissolved oxygen in the water.

Measurement using an ORP Sensor

The measurement of the redox potential is done using a redox or ORP sensor. This sensor contains a core of noble metal to which the active electrons in the water attach. The actual measurement takes place by comparing the value with a stable reference electrode. Therefore, in addition to the electrode for measuring the active electrons, each sensor also contains a reference electrode with integrated silver/silver chloride.

Additional values affecting the measurement of ORP/Redox

In addition to the redox or pH value there are some additional values to consider when measuring:

  • Temperature. The redox value is temperature-dependent. Therefore, always make sure you have more information about the temperature of the water in addition to the redox value;
  • . In swimming water, a redox value of between 600 and 800 mV is generally used as a measure to prevent bacterial development. However, this is a measure when the pH value of the bathing water is between 7 and 7.6. Therefore, measuring the pH value in addition to the redox value is also important when treating swimming water.

For many industries involved in purifying water, the redox value is very important. For example, swimming pools try to take into account a redox value between 600 and 800 mV, and when sterilising water, even values above 800 mV are considered.

Caution! Measuring the ORP value for the concentration of free chlorine in the water is an indirect value and thereby also depends on the purity of the water. Are you the manager of a public swimming pool or spa? Then always measure the concentration of free chlorine in the water instead of the redox value.

For swimming pools, the ORP value is important. Note! This is an indirect measure to measure free chlorine in the water. It is not suitable for public swimming pools

ORP Value | Increase / Decrease

The higher the ORP value, the purer the water and the less chance of polluted water. When these values are out of balance, do the following:

ORP and redox value are too low.

This means the water contains many impurities and can be a breeding ground for bacteria and viruses. If the redox value is too low and you want to increase it, you should add chlorine until the desired value is reached. When doing this, also consider the pH value of the water. This affects the effectiveness of chlorine. Also consider the water temperature.

ORP and redox values are too high.

A high ORP and redox value means that the water is pure and its purification efficiency is high. Want to lower the redox value? Then you need to lower the chlorine level in the water. For example, you can wait until the chlorine in the water has done its job and bound itself to the impurities in the water (bound chlorine). In addition, you can also break down chlorine in the water faster by exposing it to sunlight.

ORP Value | Applications

We are familiar with measuring pool ORP value or redox, but the Oxidation Reduction Potential is also used for many other industrial applications:

  • Wastewater treatment;
  • The biological purity of natural water;
  • Water purity in ponds, fish farming and aquaria;
  • For water disinfection and sterilisation (over 800 mV);
  • Purification of pool water and spa water. A redox value of between 600 and 800 mV is recommended for swimming pools;
  • Treatment of cooling water. In this, a redox value of between 300 and 400 mV is recommended.
To measure water purity in (Koi) ponds, the ORP/Redox value is used

ORP Value | Metering Pumps and Systems

Within Emec's product range, we offer various solutions for controlling the ORP/Redox value. We also offer a number of turnkey packages with dosing pumps incl. sensors. 

Dosing solutions to control ORP value 

To keep the redox value optimal, you need a pump that can dose chlorine based on the redox measurements. For dosing chlorine, we offer two dosing pumps, namely an electromagnetic pump and a motor-driven pump. Both have their own unique features. For instance, the motor-driven dosing pump offers much higher flows and is a priori suitable for industrial applications. In turn, the electromagnetic chlorine pump offers more precision in terms of dosing. More interested in a total solution? Then we also offer a dosing pump including ORP sensor.

Sensors for regulation of ORP / Redox 

As described earlier, there is a correlation between the concentration of (free) chlorine and the ORP value. In addition, the ORP value also depends on the pH value and the temperature of the water. For these all these characteristics, we offer a number of electrodes. Connected to a controller such as the Emec Centurio or the Emec LDS controller (with built-in temperature sensor), the system can then automatically regulate the ORP value in the water.

About Emec Metering Pumps

Emec is an Italian company that has specialised in dosing systems and measuring equipment for chemicals for over 35 years. This extensive experience and passion for the product is reflected not only in the reliability and innovation of the dosing systems, but also in customer focus. For example, Emec offers a 5-year warranty* (!) as well as excellent after-sale support.

* Warranty applies to the equipment and diaphragm only. Not for the wet parts such as the pump head.

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