When municipal water sources are compromised or unavailable, emergency disinfection of non-potable water is necessary to prevent illness. This process relies on adding a measured amount of household sodium hypochlorite, commonly known as bleach, to the water source. The chlorine compound works by oxidizing and destroying harmful microorganisms, such as bacteria and viruses, making the water safe for consumption. This method secures drinking water when boiling is not a practical option.
Identifying the Correct Bleach Type
Disinfecting water requires using only plain, unscented liquid chlorine bleach containing sodium hypochlorite as the sole active ingredient. Standard household concentrations typically range between 5% and 8.25% available chlorine. Check the product label for the exact concentration, as this figure is necessary for accurate dosing calculations.
Avoid any bleach product containing scents, dyes, thickeners, surfactants, or “color-safe” ingredients. These additives can be toxic when ingested and will contaminate the water. Only the liquid form should be used for this method, as powdered or granular chlorine products involve a different preparation and dosing process.
Calculating the Specific Dosage for 100 Gallons
The standard guideline for disinfecting relatively clear water using 5% to 6% sodium hypochlorite bleach is adding 8 drops per gallon. For 100 gallons, this requires a total of 800 drops of bleach. This measurement translates into practical kitchen units for simpler application.
Using the equivalent of 1/8 teaspoon per gallon, the required amount for 100 gallons is 12.5 teaspoons of bleach. This volume is roughly equal to two tablespoons and one-half teaspoon, or approximately 2 ounces of liquid bleach. This can be measured as slightly more than one-quarter of a standard measuring cup.
If the water is cloudy, colored, or extremely cold, the required dosage must be doubled. Doubling the dose ensures that enough chlorine overcomes the demand created by suspended organic matter before a residual amount is left to disinfect pathogens. For turbid water, the total requirement increases to 25 teaspoons, or about 4 ounces (one-half cup) of bleach for the 100 gallons.
Step-by-Step Purification Process
The purification process begins after the correct volume of bleach has been measured and added to the 100-gallon container. The water must be thoroughly mixed to ensure the sodium hypochlorite is evenly distributed. Mixing can be achieved by stirring the water vigorously with a long, clean paddle or by carefully rocking or rotating the container.
After mixing, the water must stand undisturbed for a minimum of 30 minutes. This contact time allows the chlorine to react with and neutralize pathogens. This is necessary for the hypochlorous acid, the active disinfectant formed by the bleach, to effectively kill harmful bacteria and viruses. Following this waiting period, a verification step is required to confirm successful disinfection.
Verification involves checking the water for a faint, residual chlorine smell, similar to a swimming pool. The presence of this odor confirms that the chlorine demand of the water has been met and a disinfecting residual remains. If no chlorine smell is detectable, the disinfection process was incomplete, likely due to high levels of organic matter.
If incomplete, the procedure must be repeated by adding half of the initial dose and waiting for an additional 15 minutes before checking the odor again. If the chlorine smell is present but too strong, the water can be aerated to reduce the intensity. Aeration is accomplished by pouring the water back and forth between two clean containers, which allows some of the excess chlorine gas to escape.
Safety Measures and Treated Water Storage
Handling concentrated liquid bleach requires safety precautions, as the product is corrosive. Bleach should be handled in a well-ventilated area to avoid inhaling strong fumes, and care should be taken to prevent contact with skin or eyes. Store the chemical securely away from children and pets.
Once the water has been successfully disinfected and verified, proper storage is necessary to maintain its quality. The purified water should be transferred into clean, food-grade containers that have tight-fitting, airtight seals. Containers that have previously held toxic substances must never be used for water storage.
Containers should be clearly labeled with the date of purification and stored in a cool, dark location to limit degradation of the residual chlorine. While properly treated and stored water can remain safe for many months, it is recommended to use or replace the stored water every six months.