Storing a personal water supply is a fundamental aspect of emergency preparedness, ensuring hydration when municipal systems are compromised or unavailable. Water itself is a stable compound, but its storage duration is determined by the container, initial purity, and the surrounding environment. The lifespan of this reserve varies significantly between commercially sealed products and water collected and treated at home. Understanding these differences and following proper preparation and maintenance steps is necessary for maintaining a safe and reliable water supply.
Commercial Bottled Water Shelf Life
Commercially bottled water is often stamped with an expiration date, typically set for one to two years after bottling, though the water itself does not technically spoil. This date is primarily a regulatory requirement reflecting quality standards and the potential for taste degradation over time. The primary factor limiting the shelf life is the plastic packaging, usually polyethylene terephthalate (PET).
The plastic container can subtly affect the water’s quality, particularly if stored improperly. When exposed to heat or stored for extended periods, the plastic can leach trace amounts of chemicals, such as antimony, into the water. The expiration date serves as the manufacturer’s guarantee of optimal taste and quality. If stored correctly in a cool, dark location, sealed bottled water can remain safe to drink past the printed date, though a stale taste may develop.
Preparing Tap Water for Long-Term Storage
The longevity of self-stored tap water depends on the initial preparation and the quality of the container used. The first step involves selecting food-grade containers, such as those made from high-density polyethylene (HDPE), which are specifically designed for consumables. Thin-walled plastics like used milk jugs are not suitable for long-term storage. Opaque containers are preferred because they block light that encourages microbial growth.
Before filling, the container must be sanitized to eliminate existing bacteria or contaminants. A common sanitizing solution is made by mixing one teaspoon of unscented household bleach with one quart of water, ensuring the solution coats all interior surfaces. After rinsing, the container should be filled with tap water, which is often already chlorinated. If the water source is unchlorinated, a final purification step is recommended using unscented household bleach at a ratio of four to five drops per gallon of water.
Duration Limits and Rotation Schedules
Stored tap water that has been properly treated should be rotated every six months. This time frame ensures the water maintains freshness and minimizes the risk of microbial regrowth as the chlorine residual dissipates. Municipal water contains disinfectants, but these compounds degrade over time, reducing their ability to suppress bacteria and algae.
Consistent rotation and re-treatment every six months allows for long-term storage. When rotating, the old water should be emptied and repurposed for non-drinking needs, such as watering plants, before the container is refilled with fresh, chlorinated water. For containers larger than five gallons, an annual check-up is required to inspect for signs of contamination like cloudiness or odor. Re-chlorination can be performed by adding four to five drops of unscented bleach per gallon when refilling the container.
Environmental Factors Affecting Potability
Even with proper initial preparation, environmental factors can shorten the usable life of stored water. High temperatures accelerate the degradation of plastic containers, promoting the leaching of compounds into the water. Storing water above 70 degrees Fahrenheit can compromise the quality and safety of the supply.
Exposure to sunlight is detrimental because ultraviolet (UV) light breaks down the chlorine residual. This loss of disinfectant allows for the growth of algae and bacteria inside the container, especially if the container is transparent. Plastic containers are slightly permeable, meaning stored water should not be located near chemicals, gasoline, or other strong-smelling substances, as the water can absorb these odors and flavors.