Does water really expire?
Water, as a pure chemical compound ($H_2O$), does not have an expiration date. It's a stable molecule that does not spoil in the same way perishable foods do. The expiration dates you see on commercially bottled water are primarily for the plastic bottle, not the water itself. Over time, chemicals from the plastic can leach into the water, and the plastic can become permeable, absorbing external odors or flavors. This is why the condition and material of the storage container are the most critical factors when considering drinking water that has been stored for a long period.
Risks of drinking year-old water
Consuming year-old water comes with several potential risks that are heavily dependent on how it was stored. The primary concerns revolve around contamination and chemical leaching.
Chemical leaching
Most single-use plastic water bottles are made from polyethylene terephthalate (PET). When exposed to heat or sunlight for extended periods, this plastic can degrade and release chemicals like bisphenol A (BPA) and antimony into the water. BPA is an endocrine disruptor, and while the amounts leached are typically small, long-term exposure is a concern. The risk increases significantly if the bottle was left in a hot car or a sunlit garage for months.
Bacterial and microbial growth
Once a water bottle has been opened, it is no longer a sterile environment. Microbes from your mouth and airborne contaminants can be introduced into the water, and over time, these can multiply. If you've been drinking directly from a reusable bottle and it's been sitting for a year without cleaning, it's very likely to harbor a high level of bacteria and even mold. Even sealed water, if stored in a warm or unhygienic place, can face contamination risks.
Contaminant absorption
Plastic is slightly porous and can absorb chemicals and odors from its surroundings. If water bottles are stored next to household cleaning products, gasoline, or other solvents, the water may absorb these chemicals. This is a significant risk for long-term storage, especially in places like a garage.
Assessing the safety of old water
Before drinking any old water, it's crucial to perform a quick safety assessment. Look for any visible signs of contamination, and use your sense of smell and taste.
Here is a checklist for determining if year-old water is drinkable:
- Visual Inspection: Hold the bottle up to the light. Is the water cloudy, or can you see any particles floating in it? Are there any signs of mold or algae growth? If yes, discard it.
- Smell Test: Open the container and smell the water. If it has a strange, musty, or plastic-like odor, do not drink it.
- Taste Test (Cautious): If the water looks and smells normal, you can try a small, cautious sip. An off or stale taste is a sign that its quality has degraded.
- Container Integrity: Check if the bottle or container is warped, cracked, or has a compromised seal. If the seal was broken or the container is damaged, the water is not safe.
Comparison of bottled vs. tap water storage
| Feature | Sealed Store-Bought Bottled Water | Treated Tap Water in Storage | Reused Plastic Bottle | Glass/Stainless Steel Container |
|---|---|---|---|---|
| Container Material | PET Plastic (single-use) | Food-grade plastic or glass | PET Plastic (repeated use) | Glass or non-corrosive stainless steel |
| Expiration Concerns | Mostly about plastic degradation and leaching, not the water itself. | Less concern with leaching if using proper containers. | High risk of bacterial growth and chemical leaching. | Minimal risk, ideal for long-term storage. |
| Storage Duration | Indefinite if stored correctly, but recommended to rotate every 1-2 years for freshness. | Up to six months with proper storage. | Not safe for long-term use after opening, even for a few days. | Can be stored safely for very long periods, indefinitely under ideal conditions. |
| Primary Risk | Chemical leaching from plastic over time and heat exposure. | Taste changes due to loss of chlorine; potential for bacterial growth. | Bacterial contamination from reuse; microplastic shedding. | Improper cleaning can introduce bacteria, but container itself is safe. |
| Best Practice | Store in a cool, dark, chemical-free area. Rotate stock. | Use clean, sealed, food-grade containers. Store in a dark, cool place. | Avoid reusing single-use bottles. Wash reusable bottles daily. | Wash and sanitize regularly. Keep sealed in a cool, dark place. |
Best practices for long-term water storage
If you intend to store water for emergency preparedness or other reasons, following best practices is essential for ensuring its safety and quality over time.
Choose the right container
- Opt for food-grade, airtight containers made of glass or high-quality, non-corrosive stainless steel. These materials do not leach chemicals or degrade over time, making them the safest option for extended storage.
- For plastic, use only new, food-grade containers that are specifically designed for long-term water storage. Never reuse a single-use PET plastic bottle for long-term storage, as they are not designed for repeated use and can break down.
Store in a proper location
- Cool and Dark: Store water in a cool, dark place with a stable temperature. Avoid attics, garages, or vehicles where heat and sunlight can accelerate plastic degradation and affect taste.
- Away from Contaminants: Ensure the storage location is away from any chemicals, such as gasoline, pesticides, or cleaning supplies. Plastic can absorb odors and chemicals from its environment, affecting water quality.
Follow a rotation schedule
- Even with the best storage practices, it's wise to rotate your water supply periodically. The American Red Cross recommends rotating commercially bottled water supplies annually.
Conclusion
In summary, the question of "Can I drink a year old water?" has a nuanced answer. The water itself is fine, but the container is the issue. If it was an unopened commercial bottle stored in a cool, dark place, it is likely safe to drink, though its taste might be affected by minor chemical interactions with the plastic. However, if it was an opened bottle, especially a reused one or one exposed to heat and sun, the risk of bacterial contamination and chemical leaching makes it unsafe to consume. Always inspect and test old water before drinking it. For emergency preparedness and optimal safety, store water in clean, food-grade glass or stainless steel containers, and follow a regular rotation schedule. When in doubt, it's always safest to pour it out.
For more information on safe drinking water practices, refer to the guidance from the Centers for Disease Control and Prevention (CDC).
