What is the difference of free chlorine and total?
Free chlorine refers to both hypochlorous acid (HOCl) and the hypochlorite (OCl-) ion or bleach, and is commonly added to water systems for disinfection. Chloramines are also known as combined chlorine. Total chlorine is the sum of free chlorine and combined chlorine.
Regardless of how frequently or what system you use to add chlorine to the water, the chlorine level should stay between 1.0 and 3.0 parts per million (ppm) to maintain a healthy pool. Any higher and you start to run the risk of red eyes and swimmers itch.
- Of course, too much chlorine can be dangerous. Exposure to over-chlorination can provoke asthma, lung irritation, and potentially skin and eye irritation. As well as being potentially bad for you, it's bad for your pool. High chlorine levels lower the pH of the water.
- This low pH can cause skin irritation and make your eyes burn if you open them under water. Like high pH, chlorine and other disinfectants aren't as effective when the pH is low, making it possible for dangerous bacteria to survive. It can also hurt your pool, causing metal to corrode and vinyl linings to wrinkle.
- If the pH is above 7, the water is basic; if it is below 7 the water is acid. The optimum pH for pool water is 7.4, since this is the same as the pH in human eyes and mucous membranes. A pH of 7.4 also gives good chlorine disinfection.
Should I swim in a pool with a “low” free chlorine level? Free chlorine is the most important number to monitor in your swimming pool water. You want it between 1.0-3.0 ppm. Free chlorine keeps the water clean and safe from harmful bacteria.
- People swimming in a pool with a chlorine level above 5 ppm will probably notice their skin, hair and eyes getting irritated or burning, and if the level is over 10 ppm, then no one should be in the pool because it is unsafe.
- If you are shocking the pool, you will have to use ½ gallon of bleach per 10,000 gallons of water to raise the chlorine levels to 5 ppm. If you are just trying to raise the chlorine level by 2.5 ppm, then you will have to use as much as ¼ gallon of bleach per 10,000 gallons of water.
- Hypochlorous acid is the active, killing form of chlorine. This is what does the real sanitizing work in your pool water. The chlorine molecule or ion kills microorganisms by slashing through the cell walls and destroying inner enzymes, proteins and processes.
Updated: 18th November 2019