In emergency situations, securing a supply of safe drinking water is critical, especially following natural disasters or contamination events. While boiling water is the most certain method for disinfection, it is often impractical for large quantities like 50 gallons. Ordinary household liquid chlorine bleach serves as a widely accepted and highly effective chemical disinfectant, capable of neutralizing most disease-causing microorganisms. This method relies on the active ingredient, sodium hypochlorite, to destroy bacteria and viruses.
Identifying Appropriate Household Bleach
The selection of the correct bleach is necessary for safety and efficacy when purifying water. Use only plain, unscented, non-color-safe, and non-gel household liquid bleach. The active ingredient must be sodium hypochlorite, with concentrations typically ranging between 5.25% and 8.25% by volume.
Avoid any bleach product containing perfumes, dyes, or added cleaners, as these extra chemicals are toxic and unsafe for consumption. Color-safe or splash-less bleach contains stabilizing agents that interfere with disinfection or are not chlorine-based. Verify the bleach has been stored for less than a year, as its potency naturally diminishes over time.
Precise Calculation for 50 Gallons
The precise quantity of bleach needed depends directly on the concentration of sodium hypochlorite in the product. For the common concentration of 5.25% to 6% bleach, the standard guideline is eight drops or approximately one-eighth of a teaspoon per gallon of clear water. Scaling this up for 50 gallons requires a total of 6.25 teaspoons of bleach.
This volume (6.25 teaspoons) is equivalent to slightly more than two tablespoons and one-quarter teaspoon of the 5.25% to 6% bleach. If using the higher concentration 8.25% sodium hypochlorite bleach, the required dosage is approximately six drops per gallon. This scales to about four teaspoons, or one tablespoon and one teaspoon, for the 50-gallon volume. Always double the calculated amount if the water is cloudy, colored, or very cold, as contaminants and temperature reduce chlorine’s effectiveness.
Step-by-Step Disinfection Procedure
Before introducing the chlorine, prepare the 50 gallons of water to ensure the bleach works efficiently. If the water is visibly cloudy or has suspended particles (turbidity), it needs pre-treatment. Turbidity consumes the active chlorine, preventing it from neutralizing microorganisms.
To remove sediment, allow the water to settle for several hours. Carefully pour the clearest water into the clean 50-gallon storage container, leaving the sludge behind. Filtering the water through a clean cloth, coffee filter, or paper towels can also help remove fine particulate matter. Once the water is clear, add the precisely measured amount of bleach directly into the container.
After adding the bleach, the chlorine must be thoroughly distributed throughout the volume of water to ensure complete microbial contact. Stir the water vigorously with a clean utensil or, if using a sealed drum, roll or shake the container to mix the contents. The treated water must then be left undisturbed for the contact time, which should be at least 30 minutes.
Confirming Successful Water Treatment
The final step is confirming the treatment was successful before consuming the water. After the 30-minute contact time, perform a simple sensory check for the presence of free chlorine residual. Properly disinfected water will have a faint, distinct odor of chlorine, similar to a swimming pool.
If you do not detect a slight chlorine smell, it indicates that organic contaminants consumed the initial dose, meaning disinfection was incomplete. Repeat the treatment by adding half of the original dosage of bleach and wait an additional 15 minutes before checking the odor again. While a strong chlorine odor suggests over-chlorination, the water is still safe to drink. The taste can be improved by pouring the water between two clean containers several times to allow some of the chlorine to dissipate.