Free Chlorine
What is this?
Free Chlorine is one of the most important factors in maintaining a clean and sanitised pool. Free Chlorine is the common name for the sanitiser that is free and available to sanitise your pool, breaking down and inactivating (killing) organic material, bacteria, and pathogens.
Maintaining free chlorine levels in your swimming pool:
Check free chlorine levels in the pool using an appropriate test kit. Correct, as necessary, by adding chlorine or increasing chlorinator hours/output.
How to calculate the necessary chlorine to add:
What you will need:
- Free Chlorine Test Result (PPM)
- Desired/Required Free Chlorine Level (PPM)
- Pool Volume (Litres)
- Concentration of the chlorine to be used (%)
Formula:
(Desired Free Chlorine Level - Free Chlorine Test Result) / Concentration of chlorine x Pool Volume / 1000 = grams/millilitres of chlorine to add
Example:
• Free Chlorine = 2
• Desired/Required Chlorine = 3
• Pool Volume = 50,000L
• Concentration of chlorine = 70% (calcium hypochlorite)
= (3 - 2) / 70% x 50,000 / 1000
= 1/0.7 x 50
= 1.43 x 50
= 71.43 grams Calcium Hypochlorite
What the free chlorine level should be:
Free chlorine levels should be maintained to between 1.0 - 5.0 PPM (parts per million). The exact chlorine requirement will vary based on many factors, such as temperature, time of day, stabiliser & phosphate levels, copper levels, number of bathers/swimmers, type of equipment used, cover usage, sun exposure, and condition of the pool.
Why is free chlorine important:
Free chlorine is vitally important to water quality and pool safety. It is responsible for sanitising the pool and inactivating bacteria, viruses, algae, and pathogens.
- If too low, the pathogens will not be inactivated and may cause illness.
- If too high, free chlorine can cause skin irritation, burns, poisoning, and (if inhaled) can cause respiratory issues. High levels may also cause damage to equipment.
Differentiation:
Free Chlorine, Chlorine, Total Chlorine, and Combined Chlorine are all different things. Understanding the difference can help you to better maintain your pool water and understand the safety concerns.
Chlorine is an element and is naturally a gas. The term chlorine is often used (some might say incorrectly) to describe any of the different forms of chlorine.
Free Chlorine, Hypochlorous Acid &/or Hypochlorite is the chemical responsible for sanitisation. It forms when chlorine combines with water.
Combined Chlorine is the result of chlorine combining with organic matter to form chloramines. This is a form of chlorine which is no longer available to sanitise.
Total Chlorine is the sum of Free Chlorine and Combined Chlorine. This is the total of all chlorine in the water.
