The 'Best By' Date and the Plastic Bottle
Most people notice a 'best by' date on bottled water and assume it means the water itself expires, but this is a common misconception. The U.S. Food and Drug Administration (FDA) states that unopened, properly produced bottled water has an indefinite shelf life. The date on the bottle typically refers to the integrity of the plastic packaging, not the water inside. Over time, particularly when exposed to heat or sunlight, the plastic can begin to degrade and leach chemicals into the water, affecting its taste and, potentially, its safety.
The Dangers of Heat and Sunlight
One of the most significant threats to stored water in plastic bottles is exposure to heat and direct sunlight. Studies have shown that high temperatures can accelerate the breakdown of plastics, causing chemicals and microplastic particles to leach into the water.
- Chemical leaching: Harmful compounds like antimony and bisphenol A (BPA) can migrate from the plastic into the water. Even some BPA-free plastics may contain other chemicals with similar health concerns.
- Microplastic contamination: Heat and UV light degrade plastic, causing it to shed billions of microscopic fragments into the water. Recent research highlights the potential long-term health risks associated with ingesting these microplastics.
The Shelf Life of Different Water Types
How long water can be stored in a plastic bottle varies depending on the type of water and whether the container is sealed or open. Correct storage is paramount for maintaining water quality and safety.
Sealed vs. Opened Bottles
- Unopened commercial bottled water: When stored in ideal conditions (a cool, dark place away from chemicals), this water can remain safe to drink for years, often up to five years, though taste may be affected over time. Many manufacturers recommend a two-year rotation schedule for best quality.
- Opened bottled water: Once opened, water is exposed to air and potential contaminants from hands and airborne microorganisms. The risk of bacterial growth increases significantly. It is generally recommended to consume opened bottled water within a few days if refrigerated, and within hours if left at room temperature. Drinking directly from the bottle introduces bacteria from the mouth, making it a breeding ground for germs.
- Tap water stored in food-grade plastic: Tap water filled and sealed in a clean, food-grade plastic container should be replaced every six months for optimal safety and freshness.
Factors Affecting Water Storage Time
Several variables influence how long water remains safe and fresh in a plastic bottle. Understanding these factors is crucial for minimizing health risks.
Comparison of Storage Containers and Conditions
| Storage Container | Typical Duration (Unopened) | Primary Risks | Best Storage Conditions |
|---|---|---|---|
| Single-Use PET Plastic Bottle | 1–2 years (for taste) | Chemical leaching, microplastic shedding, odor absorption, bacterial growth once opened | Cool, dark place, away from sunlight and chemicals |
| Food-Grade HDPE Plastic Jug | 6 months (tap water) | Leaching (less than PET), odor absorption over time | Cool, dark place; rotate stock every 6 months |
| Stainless Steel Bottle | Indefinite (water purity) | No leaching; bacterial growth if reused without cleaning | Rinse and wash daily; dry completely |
| Glass Bottle | Indefinite (water purity) | No leaching; bacterial growth if reused without cleaning; breakable | Store in a cool, dark place |
Recognizing Contamination
Before consuming water stored for an extended period, it's wise to perform a quick check for signs of spoilage. These indicators are often due to plastic degradation or the absorption of external contaminants, not the water itself going 'bad' in the traditional sense.
- Smell: Any unusual, musty, or chemical-like odor is a clear sign to discard the water.
- Taste: If the water has a stale, metallic, or plastic-like flavor, the quality has been compromised.
- Appearance: Cloudiness, discoloration, or floating particles indicate contamination or bacterial growth.
Proper Storage for Your Water Supply
To ensure your water supply remains safe and fresh for as long as possible, follow these key practices:
- Cool, Dark Location: Store bottles in a cool, dry, and dark environment, like a pantry or basement. Avoid attics, garages, or hot cars where temperatures can rise rapidly.
- Away from Chemicals: Keep water containers away from strong chemicals and fumes, such as gasoline, cleaners, and pesticides. Plastic is permeable and can absorb surrounding odors and vapors.
- Use Food-Grade Containers: For DIY water storage, use containers explicitly labeled as food-grade. Avoid reusing single-use milk jugs or other non-food-grade containers, as these can leach harmful substances.
- Rotate Stock: The Red Cross recommends rotating commercial bottled water supplies annually for best quality, while water you bottle yourself should be replaced every six months. This ensures you always have the freshest water available.
Conclusion
While water itself is not perishable, the plastic packaging can degrade over time, affecting water quality and safety. Stored under optimal conditions, unopened commercial bottled water can last for years. However, once opened or if stored improperly (especially in heat), bacterial contamination and chemical leaching become significant risks. For safe drinking, consume opened bottles quickly and practice proper storage for unopened reserves. For the longest, safest storage, consider using non-plastic alternatives like glass or stainless steel. Prioritizing proper storage and container choice ensures your drinking water remains clean and healthy for you and your family.
For further guidance on emergency water supply preparation, refer to the CDC.
Key Practices for Water Storage
Mind the Plastic Degradation: The 'best by' date on a bottle refers to the degradation of the plastic, not the water's expiration, especially when exposed to heat or sunlight. Choose Ideal Storage Conditions: Keep all water bottles in a cool, dark place, away from direct sunlight and potent chemicals, to slow down plastic degradation and chemical leaching. Understand Opened vs. Sealed Timeframes: Consume opened bottled water within a few days (refrigerated) or hours (room temp) due to the risk of bacterial contamination. Sealed bottles can last years under proper conditions. Avoid Reusing Single-Use Plastics: Refilling single-use bottles is unhygienic due to the porous plastic harboring bacteria and is not designed for repeated use, leading to greater chemical leaching. Use Safe Long-Term Containers: For long-term water storage, opt for food-grade containers made from durable plastic, glass, or stainless steel, and rotate the water supply regularly. Check for Signs of Spoiled Water: Always inspect water stored for long periods for odd smells, tastes, or cloudy appearances before drinking. Minimize Microplastic Exposure: Reducing reliance on single-use plastic bottles, especially after they've been heated, can help lower your ingestion of microplastic particles.
FAQs
Question: How long is bottled water safe to drink after the 'best by' date? Answer: Bottled water is generally safe to drink well after the 'best by' date if stored properly in a cool, dark place. This date primarily indicates optimal quality and taste, not safety. However, the water's taste may degrade over time due to slow plastic leaching.
Question: Why do plastic bottles have an expiration date if water doesn't expire? Answer: The date is mandated by some state laws, but mostly serves as a manufacturer's guideline for optimal product freshness. It accounts for the eventual degradation of the plastic bottle, which can impact the water's taste and quality over extended periods.
Question: Is it safe to store bottled water in a hot car? Answer: No, it is not safe to store bottled water in a hot car. High temperatures dramatically accelerate the leaching of chemicals like antimony from the plastic bottle into the water, and microplastic shedding is also significantly increased.
Question: What are the risks of reusing a single-use plastic water bottle? Answer: Reusing single-use plastic bottles poses two main risks: a high risk of bacterial contamination from repeated mouth contact and improper cleaning, and increased chemical leaching from the plastic as it degrades from wear and tear.
Question: How long can I store tap water in a plastic container at home? Answer: Tap water stored in a clean, tightly sealed, food-grade plastic container should be replaced every six months. Ensure it is kept in a cool, dark place to maintain freshness.
Question: Can I store water in plastic containers that previously held other liquids? Answer: No, you should not use plastic containers that have previously held milk, juice, or toxic chemicals, even if washed thoroughly. Residue can remain and contaminate the water over time.
Question: What is the best way to store water for long-term emergency use? Answer: For long-term emergency use, store water in FDA-approved, food-grade storage containers, away from light and chemicals. Alternatively, glass or stainless steel containers are excellent choices as they are non-porous and won't leach chemicals. Regularly rotate your stock every year.
