How to Read Pool Chlorine Levels

Chlorine is added to pool or hot tub water to kill germs and prevent your swimmers from becoming sick. Free chlorine can kill most germs within a few minutes if used properly. To determine your pool’s chlorine levels, dip a test strip in the pool for a few seconds and then match the resulting color of the strip to a chart linked to “parts per million” chlorine levels.

Some pool test kits measure “free chlorine,” while others measure both “free chlorine” and “total chlorine.” There is a difference between “free” and “total” chlorine. The free chlorine level is a measure of how much chlorine is available in pool water to destroy germs. Chlorine that reacts with swimmer perspiration, urine, body oils and cosmetics produces “combined chlorine,” which is mostly unavailable to destroy germs. The total chlorine level is the sum of the free chlorine and combined chlorine levels in the pool. For a healthy pool, the free chlorine level should be between 1.0 and 3.0 parts per million (ppm). The Centers for Disease Prevention and Control recommends pH 7.2–7.8 for pools and hot tubs. Keeping the pH level in this range helps prevent recreational water illnesses and infections, such as diarrhea, gastrointestinal, skin, ear, respiratory, eye, neurologic and wound infections. A healthy pH level also promotes the lifespan of the pipes, and swimmers’ comfort. Anything below pH 7.0 is bad for the health of your pool and swimmers, causing eye and skin irritation.

As pool or hot tub owners, it’s important to routinely test and adjust both the free chlorine concentration and pH. The best way to kill germs is by properly maintaining the free chlorine concentration and pH. This will help prevent the spread of germs that cause recreational water illnesses.

If you have questions about pool maintenance, contact Swim-mor or fill out our contact form.