Chlorine in Drinking Water

🩨 Health Effects

Chlorine at levels used for disinfection is generally considered safe. Above the MCL, it can cause eye and nose irritation and stomach discomfort. Chlorine taste and odor is an aesthetic complaint, not typically a health concern at permitted levels.

📍 Sources in Water

Chlorine is added intentionally to drinking water to kill bacteria, viruses, and other pathogens. It is the most widely used drinking water disinfectant in the US and has dramatically reduced waterborne disease since its introduction in the early 1900s.

✅ What To Do

Chlorine smell and taste can be reduced by using an activated carbon filter or by refrigerating water in an open pitcher. No health action is needed at permitted levels. An MCL violation for chlorine means the utility overdosed, which is unusual.

📜 Regulation History

The EPA set the maximum residual disinfectant level (MRDL) for chlorine at 4 mg/L under the Stage 1 Disinfectants and Disinfection Byproducts Rule in 1998. Chlorination of public water supplies began in Jersey City, NJ in 1908 and is credited with eliminating most waterborne disease epidemics in the US. The WHO guideline is 5 mg/L, less strict than the US standard.

🔬 How To Test Your Water

Free chlorine test kits using DPD reagent are widely available at pool supply and hardware stores for $8-$15. Digital colorimeters provide more precise readings ($30-$80). Lab testing is generally not needed since your utility reports chlorine residual levels. Taste and smell thresholds are typically around 0.3-0.5 mg/L.

💧 Which Filters Remove Chlorine?

Standard activated carbon filters (NSF/ANSI 42 certified) effectively remove free chlorine taste and odor. Both pitcher filters and faucet-mounted carbon filters work well. Whole-house carbon filters remove chlorine from all taps and showers. Reverse osmosis systems also remove chlorine as part of their multi-stage filtration.

🔗 Related Contaminants