Redox regulation
for salt water pools
Redox regulation stabilises the Redox potential of the pool water and ensures comfortable bathing conditions.
Redox regulation
Redox is the potential for disinfection of pool water.
When correctly regulated, the Redox potential offers swimmers a clear water free of viruses and bacteria.
Here is how to measure and regulate it, then draw benefit to maintain clean and hygienic water in your pool!
What is the Redox potential?
Redox (potential for oxidation and reduction) regulation serves to control the oxidising power of the aquatic environment and therefore optimise its disinfection.
In most private and public pools, chlorine is the most commonly used oxidiser.
Treating water with chlorine prevents the development of green micro-algae and is efficient at eliminating bacteria.
Nonetheless, to prevent green, cloudy, or opaque water, it’s not just a question of pouring a large quantity of chlorine into your pool.
If there is too much chlorine in the pool, the liner will become discoloured and the equipment will degrade rapidly.
Swimmers will soon have itchy or irritated skin and eyes.
The Redox regulator permanently tests and adjusts the level of chlorine in the pool to avoid excessive or insufficient levels.
Redox regulation is effective for all types of pool and all the more recommended for indoor pools or sheltered pools, as the residual effect of chlorine is longer.
This means there is an additional risk of over-chlorination.
Redox potential is a very easy and effective way to control the quality of your pool water.
It is even mandatory in some countries.
The system is reliable and rapid, thanks to the Redox sensor placed in the pool water circuit. The result is reported in millivolts.
How does a Redox regulation system work?
Redox is an abbreviation of Reduction – oxidation.
Redox potential is a measurement of capacity: i.e. the oxidation capacity of the water.
People also often speak of ORP for Oxidation Reduction Potential.
OK, but what is the oxidation capacity of water?
Without going back to chemistry classes, we have learned that in terms of swimming pools, the oxidation capacity of water refers to its disinfection capacity.
i.e. the capacity of water to kill bacteria, germs, etc.
Sufficient oxidation capacity means that water is considered to be disinfectant, so we can swim with peace of mind!
The Redox regulation is either coupled to an electrolyser or to a liquid chlorine injection system.
The Redox sensor constantly measures the oxidisation of the pool water.
When the sensor reading reaches the specified set point, the Redox unit instructs the electrolyser to stop the production of chlorine or instructs the chlorine pump to stop injecting it.
When the Redox reading is below the set point, chlorine production starts up again.
Why and how do I manually test the chlorine level in the pool?
Even when we use automated regulation appliances, prudence is absolutely necessary!
So to make bathing safe and to confirm that the regulator sensor reading is exact, it is advised to take one independent measurement of the Redox potential at least once a week in addition to the automated regulator.
It sometimes occurs that the Redox sensor has difficulty in measuring the chlorine potential of a pool, especially if excess organic materials accumulate on the sensor.
Three chlorine level test methods
There are three methods for measuring the level of chlorine.
All three require leaving the pool filtration system active for at least 30 minutes, which mixes the water up suitably.
Then, water must be sampled at a depth of 30 cm, which is the same as wetting half your forearm.
The three types of analysis are:
- Chlorine test strips
Simple and cheap. This method consists simply in dipping the strip into a cup of pool water like for a pH test.
Then, hold the strip horizontally for a few seconds (depending on the instructions given on the bottle) and compare the colours on the strip with those on the bottle.
Check the expiry date on the packaging and store the test strips in a dry place.
- Liquid analysis kit
This chlorine test kit comprises a liquid reagent.
Simply mix the pool water with the number of drops of reagent indicated in the instructions, then compare the colour of the precipitate with the index provided in the packet.
The result will be shown clearly.
Fill the test tube to the level shown, add the number of drops of reagent specified by the manufacturer and compare the colour of the precipitate in your water with the indications in the documentation.
Check the expiry date of your reagent.
- ORP electronic tester
The electronic tester is the simplest solution to measure the Redox potential of your pool yourself.
Firstly it must be calibrated by dipping it in a reference solution, then immerse the sensor part of the tester in the pool water and read the value displayed on the screen.
The tester must be calibrated with a reference solution.
Why, when and how do I calibrate the Redox sensor?
The sensor is a measuring instrument which defines the oxidising power of the pool water.
Depending on the reading and the specified set point, the electrolyser might be activated or not and the pump might inject disinfectant or not.
The sensor might drift over time and needs precise references to produce accurate measurements, hence the calibration.
Three reasons to calibrate a Redox sensor:
- When commissioning the appliance or whenever the pool is opened.
- When the sensor is observed to be inaccurate (observation made using another ORP reading).
- When replacing a worn sensor with a new one.
Calibration is done using a precise reference solution.
Ensure this solution is protected from pollution, hence the importance of rinsing the sensor with clean water and delicately wiping it dry before dipping it in the reference solution.