Maintaining balanced water is critical to enjoying your pool, but when it comes to quick water management it is hard to find a boiled down guide of what you really need to keep an eye on. Here is my attempt to help with chlorine levels in your pool:
In most pools the primary sanitizer is chlorine. Chlorine is measured in three different categories depending on what you are using to test your water, these are free, combined, and total chlorine levels.
Free Chlorine is what you really want to have a bit of in your water. This is the chlorine available to attach to and kill bacteria, viruses, and other organisms in your water. Ideal levels of Free Chlorine range from 1.0-5.0 ppm. I would recommend trying to stay on the lower end of this if possible due to the irritating nature of chlorine as it reacts with your body.
Combine Chlorine is “used up” chlorine or what is left behind when a chlorine molecule attaches to and neutralizes an organism. The target number for this type of chlorine is 0.0 ppm, but a true 0 is functionally impossible to get because there will always be something for a chlorine molecule that is free to attach itself to. To remove Combined Chlorine from your system you will need to oxidize your water which can be done by “shocking” your pool or by employing supplemental sanitation/oxidation such as UV or Ozone treatment.
Total Chlorine is a measure of all chlorine in your water and is only functionally measure to find your Combined Chlorine figure. Many reagent sets will give you a Total Chlorine and Free Chlorine numbers, so you really just need to remember that Combined = Total – Free.
By Will McMordie