Chlorine tablets offer a rapid and effective method for disinfecting water sources in emergency situations or when traveling. Their primary function is to neutralize biological pathogens, such as bacteria, viruses, and some cysts, that cause waterborne illnesses. These tablets provide a portable solution for transforming potentially unsafe water from streams, rivers, or wells into water that is safe for consumption. Understanding the proper chemical composition and application steps is necessary for successful purification.
Choosing Purification Tablets
Modern water purification tablets primarily rely on Sodium Dichloroisocyanurate (NaDCC) as their active ingredient. NaDCC is preferred over older methods, such as iodine or liquid household bleach, due to its greater stability and ease of handling in solid tablet form. NaDCC is not chlorine itself but reacts with water to release hypochlorous acid, the potent germicide known as “free available chlorine.” This formulation provides a precise and controlled dose of disinfectant, which is an advantage over using liquid bleach where measuring accuracy can be difficult. When selecting a product, look for certification from bodies like the U.S. Environmental Protection Agency (EPA) or confirmation that the compound is certified to NSF/ANSI Standard 60, which verifies its suitability for drinking water treatment.
Step-by-Step Water Treatment Process
The initial step involves pre-filtering any visibly turbid or cloudy water to remove large particulate matter. Using a clean cloth, coffee filter, or other fine material to strain the water helps the chemical disinfectant work more efficiently. Organic materials can consume the free available chlorine, and the process effectiveness relies on the chemical coming into direct contact with the pathogens, which is hindered by suspended solids.
Once the water is relatively clear, determine the correct dosage, typically one tablet per one liter or one quart of water. Drop the tablet into the measured volume and allow it to fully dissolve, which happens quickly due to the effervescent base. After dissolving, the container must be mixed thoroughly by shaking or stirring to ensure the disinfectant is distributed evenly.
A critical contact time is required for the hypochlorous acid to oxidize the cellular structures of microorganisms, rendering them harmless. The minimum wait time is generally 30 minutes before the water should be consumed. Very cold water or water with a high level of organic contamination may require a longer contact time to ensure complete disinfection. While highly effective against bacteria and viruses, efficacy against certain parasitic cysts, like Cryptosporidium, may require higher doses or a combination with filtration.
Safety and Storage Guidelines
Chlorine purification tablets are concentrated chemicals that must be handled with care and stored securely away from children and pets. Proper storage is paramount to maintaining the tablets’ potency, requiring a cool, dry, and dark location, ideally in their original moisture-resistant packaging. Exposure to humidity or extreme temperatures can cause the tablets to degrade prematurely.
Most NaDCC tablets have a shelf life ranging from three to five years when the packaging remains unopened. Once opened, the shelf life is significantly reduced, often to about one year, as the tablets react with moisture in the air. Handling precautions include avoiding skin and eye contact and ensuring the tablets are never mixed with acidic solutions or certain detergents, which can release toxic chlorine gas.
Addressing Taste and Water Quality Limitations
While chlorine tablets effectively eliminate biological threats, they do not address all potential water quality issues, as they are not designed to remove chemical contaminants. The tablets will not filter out heavy metals, pesticides, or man-made organic pollutants. If the water source is suspected to contain such contaminants, disinfection alone is insufficient, and a separate filtration method is recommended.
The presence of residual chlorine, which is necessary to confirm successful disinfection, often imparts a noticeable taste and odor to the treated water. If the water does not smell faintly of chlorine after the minimum contact time, the dose may have been insufficient or the water contained too much organic matter, requiring the treatment process to be repeated. To improve the taste, the water can be aerated by pouring it back and forth between two clean containers or by shaking the sealed container vigorously.
This aeration process allows the excess chlorine gas to off-gas, making the taste more palatable. Alternatively, a small amount of a flavored drink mix can be added to mask the taste of the residual disinfectant. These tablets are a method of disinfection—they kill pathogens—but they do not remove the physical particles that make water murky, reinforcing the necessity of pre-filtration.