In modern urban water supply systems, chlorine is an almost indispensable component. Whether you live in a major city or a small town, the tap water you drink every day usually contains a certain level of chlorine. This is not a contaminant but a deliberate addition made for public health safety. So, why is chlorine added to tap water? Is it safe for human consumption? And how can we remove its taste or smell if needed? Let’s explore these questions in detail.
Why Is Chlorine Added to Tap Water?
Chlorine is a powerful disinfectant that has been widely used in drinking water treatment since the early 20th century. The main reason for adding chlorine is to kill harmful microorganisms such as bacteria, viruses, and parasites that may be present in the water. If left untreated, these pathogens could lead to serious illnesses like cholera, typhoid, and dysentery.
In water treatment plants, chlorine is typically added at the final stage of treatment to ensure that water remains sterile throughout the entire distribution system, from the plant to the consumer’s tap. This ongoing disinfection effect is referred to as residual chlorine protection.
How Much Chlorine Is in Tap Water?
Although chlorine is effective in eliminating pathogens, excessive exposure can have negative health effects. Therefore, governments around the world regulate chlorine concentrations in drinking water.
For example, in the United States, the Environmental Protection Agency (EPA) has set the maximum residual disinfectant level (MRDL) for chlorine at 4 milligrams per liter (mg/L) or 4 parts per million (ppm). This level is considered safe based on extensive research.
In China, the “Standards for Drinking Water Quality” (GB5749-2022) require that free chlorine should not be less than 0.3 mg/L at the water treatment plant and no less than 0.05 mg/L at the end of the distribution system. Generally, chlorine levels are maintained between 0.3 to 1.0 mg/L. The slight bleach-like smell that some people notice in tap water is due to this low concentration of chlorine.
Is Chlorine in Tap Water Safe?
Overall, chlorine in tap water is safe within regulated limits. Most people can consume chlorinated water with no adverse effects. However, some individuals may be sensitive to chlorine and may notice an unpleasant taste or odor, or experience dry skin or eye irritation when showering.
Additionally, chlorine can react with natural organic matter in water to form disinfection byproducts such as trihalomethanes (THMs). Some studies have linked long-term high exposure to these compounds with potential health risks, including cancer. However, modern water treatment technologies have significantly reduced these byproducts to levels well below health safety standards, so there is no need for alarm.
How to Monitor Chlorine Levels?
To precisely control chlorine concentrations in drinking water, especially in water treatment plants and secondary distribution systems, professional instruments like residual chlorine analyzers are widely used. For example, Apure offers advanced online chlorine analyzers capable of continuously and accurately monitoring free chlorine, total chlorine, and chlorine dioxide levels in water.
Key features of Apure chlorine analyzers include:
- High-precision sensors with fast response times
- Automatic temperature compensation for stable readings
- Integration with dosing systems for smart chlorine adjustment
- Applications in water plants, municipal supplies, buildings, and swimming pools
If you work in water treatment or manage a residential or commercial facility, using a high-quality chlorine analyzer not only ensures water safety but also helps reduce disinfectant overuse and lower operational costs.
How to Remove Chlorine from Tap Water?
If you are sensitive to the taste or smell of chlorine, or if you’re using the water for pets, aquariums, or plants, you can use the following methods to remove chlorine:
- Let the water sit: Leave water in an open container for several hours or overnight, and the chlorine will naturally evaporate. Using a wide-mouth container speeds up the process.
- Activated carbon filters: Filters such as Brita or PUR effectively remove chlorine and improve taste.
- Reverse osmosis (RO) systems: These systems thoroughly remove chlorine along with other dissolved substances.
- Boiling: Boiling water for 10–15 minutes can remove most chlorine (note: this does not work well for chloramine).
- Vitamin C tablets: Vitamin C neutralizes chlorine and is commonly used in aquariums.
Chlorine vs. Chloramine
In recent years, some regions have switched to using chloramine (a combination of chlorine and ammonia) instead of chlorine. Chloramine is more stable, lasts longer in the distribution system, and produces fewer byproducts. However, it is harder to remove and may require specialized filters labeled for chloramine removal.
Summary
The presence of chlorine in tap water is a necessary public health measure that ensures the microbiological safety of drinking water. While it may cause minor taste or smell issues for some individuals, chlorine levels are carefully regulated and considered safe.
If you are looking for real-time monitoring of chlorine levels, investing in a residual chlorine analyzer, such as those from Apure, is a smart choice for ensuring water safety and process efficiency.