1. What are total chlorine and combined chlorine?
Total chlorine is the total amount of chlorine present in your pool. It is made up of :
Free active chlorine: that which is available to disinfect the water.
Combined chlorine: The by-products (notably chloramines) formed when chlorine reacts with organic matter.
A high level of combined chlorine indicates a high organic load in the water. In France, legislation requires combined chlorine levels to be below 0.6 ppm.
2. What is the breakpoint?
The breakpoint is the chlorine concentration that must be reached for the added chlorine to become free active chlorine, available for effective water disinfection. Before reaching this point :
Chlorine oxidizes mineral compounds (such as iron and manganese). This can temporarily turn the water brown due to the iron.
Chlorine reacts with organic compounds, forming chloramines, responsible for chlorine odors and eye irritation.
Once a certain chlorine concentration has been reached, the chloramines are destroyed and the odours fade.
An indicator that the breakpoint has been reached? Water without persistent chlorine odors, where chlorine is fully effective in disinfecting.
3. How long do chlorine odors persist?
Chlorine odors last until chloramines are eliminated. In general :
Odors diminish sharply in the first hour after chlorine is added.
They disappear completely after around 24 hours, depending on the organic load and the dose of chlorine used.
4. Conclusion
The breakpoint is a key stage in pool water management. By reaching this critical chlorine concentration, you eliminate chloramines and ensure optimum disinfection. When properly controlled, this process guarantees healthy, pleasant water, free from unpleasant odors!