The Science Behind Bottled Water's "Expiration"
Water is a simple chemical compound, H₂O, that fundamentally does not expire. The "best by" dates often printed on water bottles are for the container, not the contents. This is because the container, typically made from Polyethylene Terephthalate (PET), can degrade over time. The degradation process accelerates significantly with exposure to heat and sunlight, which can cause chemicals from the plastic to leach into the water. Chemicals like antimony, used as a catalyst in PET production, and various phthalates, can migrate into the stored water. While the levels are generally low and not immediately hazardous, prolonged exposure and improper storage increase the concentration of these compounds and can significantly affect the water’s taste and odor. This chemical alteration is the primary reason why five-year-old bottled water is questionable, even if the water itself is timeless.
How to Determine if Your Old Bottled Water is Safe
Before consuming any old bottled water, a simple sensory check is the best first step. Look for any signs of contamination, discoloration, or cloudiness. The water should be perfectly clear. Any visible sediment or a change in color, such as a greenish tint, is a clear sign to discard it. Next, give it a good sniff. If there is a musty, chemical, or plastic-like odor, the plastic has likely degraded and affected the water. Finally, taste a very small amount. A metallic or stale taste indicates the water is no longer fresh due to chemical leaching. It is important to note that if the bottle's seal has been broken at any point, the risk of contamination from airborne pathogens increases dramatically. In such cases, the water should be disposed of immediately. Always inspect the bottle itself for any cracks, damage, or compromised seals. A damaged container means the contents have been compromised.
Storage Conditions: The Most Critical Factor
The longevity and safety of bottled water are almost entirely dependent on how it has been stored. The International Bottled Water Association and public health organizations like the CDC provide clear guidelines for proper storage.
- Location: Store water in a cool, dark, and dry place. A basement or climate-controlled pantry is ideal. Avoid storing water in garages, attics, or vehicles, where temperature fluctuations are common and can become extreme.
- Proximity to Chemicals: The porous nature of plastic means it can absorb odors and chemicals from its surroundings. Water bottles should be stored far away from household cleaners, gasoline, paints, and other solvents.
- Sunlight Exposure: Direct sunlight, especially prolonged exposure, is detrimental to the integrity of plastic bottles. UV rays accelerate the breakdown of PET plastic, leading to faster chemical leaching.
- Temperature Stability: Maintaining a stable temperature is key. Both excessive heat and freezing can degrade the plastic over time and alter the water's taste. Some experts suggest consuming water stored in hot conditions within one year, while properly stored water is fine for much longer.
Old vs. Fresh Bottled Water: A Comparison
| Aspect | Fresh Bottled Water (Properly Stored) | 5-Year-Old Bottled Water (Potentially Improperly Stored) |
|---|---|---|
| Purity | Highest level of purity, as intended by manufacturer. | Possible chemical leaching from the plastic bottle, altering purity over time. |
| Taste | Crisp and clean, untainted by container. | May develop a stale, metallic, or plastic-like taste due to container degradation. |
| Odor | Odorless, as expected of pure water. | May have a chemical or musty odor if plastic has degraded. |
| Safety | Considered safe for consumption. | Generally safe if stored ideally, but risks increase with improper storage (heat, light). |
| Bottle Integrity | Sealed and intact, with plastic at its most stable. | Plastic may show signs of degradation; seals may be compromised. |
| Health Risk | Negligible risk. | Low risk if stored ideally; increased risk from higher chemical concentrations and potential contamination if seal is compromised. |
The Verdict: Drinking Old Bottled Water
For an unopened bottle of water that has been stored in cool, dark conditions, the water is technically still safe to drink after five years. The taste, however, may be compromised. For water that has been exposed to heat or sunlight, the risk of consuming higher levels of leached chemicals makes it unadvisable to drink. In such cases, the water may still have non-potable uses. If you are concerned about long-term storage, consider storing water in glass or stainless-steel containers, which are non-porous and do not leach chemicals. For emergency preparedness, it is generally recommended to rotate stock every one to two years to ensure the freshest and highest-quality water supply.
What to Do with Old Bottled Water
If your five-year-old bottled water fails the sight, smell, or taste test, don't just dump it. Here are some safe and practical alternatives:
- Household Cleaning: Use the water for cleaning floors, washing windows, or rinsing dishes.
- Gardening: Water your plants, especially if you have an area with non-edible plants. It's a great way to avoid wasting a resource.
- Toilet Flushing: In a non-emergency, the water can be used to flush toilets.
- Emergency Uses: Keep the water for washing hands or for hygiene purposes during a non-potable water emergency.
Conclusion
While water itself has an unlimited shelf life, the plastic bottle's limited lifespan and its susceptibility to environmental factors are the real reasons to question if 5 year old bottled water is still good. The key takeaway is that proper storage is paramount. If your bottles have been stored in a cool, dark place away from chemicals and extreme temperatures, the water is likely safe to drink, though its taste might be off. If you have any doubt about the storage conditions or if the water has a noticeable odor or taste, it is safest to use it for non-potable purposes. Prioritizing fresh supplies and proper storage practices ensures the best quality and safety for your drinking water over the long term. For more detailed guidelines on water storage, the Centers for Disease Control and Prevention provides guidance on safe water storage for emergencies.
