Water Testing Myth: Smelling Chlorine?
When I was a kid (some “friends” would say that was before electricity or indoor plumbing was invented), I distinctly remember going to the local community pool and smelling the odor of chlorine as I neared the entrance.
My parents would always say something like “oh, they just added chlorine so the water’s safe to swim in.” Of course I ALWAYS believed what my parents told me (at least until I was 14 or 15), so I happily jumped in the pool. Later, after the rashes appeared and my eyes were red, we just chalked it up to a mysterious something that caused it.
Fast forward too many decades and add almost 26 years in the pool/spa industry, I now, realize it wasn’t too much chlorine but rather too much “COMBINED chlorine” (aka chloramines) in the water that was causing that strong chlorine odor and the resulting rashes and irritation.
Remember, any form of chlorine that is added to water has the exact same chemical reaction; it produces hypochlorous acid (HOCl) and a hypochlorite ion (OCl-) — otherwise known as “free chlorine.” Free chlorine is what protects bathers by destroying germs, algae, and other contaminants in the water.
However, when the free chlorine reacts with organic contaminants, it forms chloramines, which we also refer to as “combined chlorine.” Chloramines are much weaker sanitizers and oxidizers than free chlorine. So where do the organics come from? Our sweat and urine contribute to the organics in the water, and so do things like personal care products, pollen, dirt, dust, and lawn fertilizers.
Chloramines are responsible for the typical “chlorine smell” we find in pool and spa waters. This is NOT a good thing, especially in indoor environments where the exchange of fresh air is poor or non-existent. So … how do you tackle this problem? Breakpoint chlorination! Although it seems odd, you’re actually adding more chlorine to eliminate the combined chlorine. To determine how much chlorine to add to achieve breakpoint, take your combined chlorine value and multiply that number by 10. The resulting number is how many parts per million (ppm) of chlorine that needs to be added ALL AT ONCE to remove the combined chlorine. For example, if your combined chlorine test result is 0.5 ppm, you would multiply your result by 10, which will determine how much chlorine is needed to reach breakpoint (0.5 x 10 = 5.0 ppm). So, it will take 5 ppm of chlorine. Consult dosage charts to determine the correct amount of chlorine to add based on how many gallons of water. Remember to keep pumps and filters running while doing this.
Some final words of wisdom:
1. NEVER add chlorine to a skimmer. Add chlorine in front of a return line to help it disperse throughout the water.
2. NEVER breakpoint chlorinate with stabilized chlorine (dichlor or trichlor). Only use sodium hypochlorite, lithium hypochlorite, or calcium hypochlorite. Using dichlor or trichlor will add large amounts of stabilizer (cyanuric acid) to the water that may cause other problems.