How Long Can Still Water Be Stored?

December 9, 2025 •

4 min read

According to the U.S. Food and Drug Administration (FDA), bottled water has an unlimited shelf life if properly produced and sealed. But this indefinite longevity applies only when stored correctly; the primary concerns for how long can still water be stored are the container material, storage conditions, and potential contamination after opening.

Quick Summary

The lifespan of still water depends on its container and storage environment, not the water itself. Unopened, properly stored bottled water can last years, but opened containers or improperly stored water pose risks of contamination and chemical leaching from plastic. Proper storage involves cool, dark conditions in food-grade materials like glass or stainless steel.

Key Points

Water doesn't expire, but the container does: The 'best by' date on bottled water relates to the plastic packaging, not the water itself.
Proper storage is crucial: Keep water in a cool, dark place away from chemicals to prevent contamination and plastic leaching.
Opened bottles have a very short life: Once opened, water becomes susceptible to bacteria and should be consumed within 1-2 days.
Glass and stainless steel are superior containers: These materials are non-porous and do not leach chemicals, making them ideal for long-term storage.
Store-bought water can last years: When sealed and stored correctly, commercial bottled water can last for years beyond its printed date.
Homemade stored water needs rotation: If storing tap water, use food-grade containers and rotate the supply every six months.
Discard if it looks or smells off: Any unusual odor, taste, or appearance in stored water indicates potential contamination.

Understanding Water's Longevity: It's About the Container

Water ($H_2O$) is a stable chemical compound and does not inherently expire or 'go bad'. The common misconception comes from the expiration dates found on bottled water, which are a regulatory formality designed to track stock rotation and account for the eventual degradation of the plastic packaging. The real enemies of stored water are light, heat, and air, all of which compromise the integrity of the container and introduce potential contaminants.

Commercially Bottled Still Water

When purchased and left sealed, commercially bottled water has an exceptionally long shelf life, often a few years, because it is bottled under sterile conditions. The primary threat is the slow leaching of chemicals like bisphenol A (BPA) and microplastics from the polyethylene terephthalate (PET) plastic into the water, a process accelerated by heat and sunlight. This leaching can affect the taste and, over time, potentially pose health risks. For maximum freshness, it's best to consume bottled water within the manufacturer's recommended timeframe, typically two years.

At-Home Stored Water

For emergency preparedness, many people store tap water. Properly prepared tap water can be stored safely for about six months. After this period, the water should be replaced to ensure optimal taste and purity. The chlorine that keeps public tap water safe for a short period will dissipate over time, allowing bacteria to grow. If storing tap water, it's crucial to use clean, food-grade containers made from materials that won't taint the water. Glass and stainless steel are superior options to plastic for long-term storage, as they are non-porous and won't leach chemicals.

The Dangers of Contamination

Once a water bottle or container is opened, its shelf life drastically decreases. Every time you take a sip, you introduce bacteria from your mouth into the water. This is why a water bottle left in a gym bag for a few days can develop a musty smell or stale taste. Airborne microorganisms, dust, and other contaminants can also enter and multiply in open containers, especially in warmer conditions. Experts recommend consuming opened bottled water within a day or two, and storing it in a cool place like a refrigerator to slow bacterial growth.

Factors Influencing Still Water Storage

Container Material: Food-grade glass or stainless steel are the best options for long-term storage as they are non-porous and do not leach chemicals.
Storage Temperature: Store water in a cool environment, ideally between 50°F and 70°F (10°C–21°C). Heat accelerates the degradation of plastic and promotes microbial growth.
Light Exposure: Keep water containers away from direct sunlight. UV light can degrade plastic and promote algae growth.
Environmental Proximity: Store water away from household chemicals, gasoline, or cleaning products. Plastic containers are slightly permeable and can absorb surrounding odors.

Proper Storage Guidelines for Different Container Types


Storage Container Type	Recommended Shelf Life (Unopened)	Key Safety Considerations
Commercial Plastic Bottles	Up to 2 years, often indefinitely safe with proper storage.	Leaching of plastic chemicals is a concern, especially when exposed to heat or light. The 'best by' date is for taste and quality.
Home-Filled Food-Grade Plastic	6 months.	Use designated food-grade containers, not old milk jugs. Treat with household bleach for long-term emergency storage.
Glass or Stainless Steel	Indefinitely safe, with minimal risk of taste alteration.	Excellent for long-term storage, but glass can break. Ensure lids are rust-proof and airtight.
Opened Bottle (Plastic)	1-2 days.	High risk of bacterial contamination from mouth and air. Refrigerate to extend freshness. Discard if it develops an off odor or taste.

A Final Word on Water Storage

While water itself is essentially timeless, its safety and freshness in storage are not. The longevity of stored water is entirely dependent on the container and the conditions in which it's kept. By selecting the right storage vessel and following a few simple guidelines—like keeping it cool, dark, and sealed—you can ensure your water remains fresh and safe to drink for years to come. Remember to always inspect and rotate your emergency water supply regularly to maintain the highest quality.

For more detailed information on emergency water treatment and storage, visit the official Centers for Disease Control and Prevention website: https://www.cdc.gov/water-emergency/about/how-to-create-and-store-an-emergency-water-supply.html.

Conclusion

Understanding how long still water can be stored correctly is vital for both everyday hydration and emergency readiness. The key takeaway is that the container, not the water, is the main variable. Commercially bottled water is safe for a significant period when unopened, while self-stored water requires proper container selection and periodic rotation. By avoiding heat, light, and contamination, you can ensure a reliable, safe water supply whenever you need it.

Frequently Asked Questions

Yes, it is generally safe to drink unopened bottled water past its 'best by' date if it has been stored properly in a cool, dark place. The date primarily indicates when the plastic bottle might begin to affect the water's taste, not its safety.

Once opened, still water should be consumed quickly, ideally within 1 to 2 days. The act of drinking from the bottle introduces bacteria, and refrigeration is recommended to slow bacterial growth.

A glass of water left out overnight is unlikely to be unsafe, but it may taste 'stale' due to dissolved carbon dioxide and a potential lack of chlorine. Covering the glass can prevent dust and airborne contaminants from entering.

Store tap water in clean, food-grade containers in a cool, dark place, away from chemicals and sunlight. For long-term storage, the CDC recommends replacing the water every six months.

Yes. While the water itself is timeless, glass is non-porous and doesn't leach chemicals, preserving the water's quality and taste indefinitely, unlike plastic which can degrade over time.

Yes, heat is a major factor affecting stored water. High temperatures accelerate the degradation of plastic, causing chemicals and microplastics to leach into the water, affecting both its taste and potentially its safety.

You can check for signs like a strange odor, a musty or off-putting taste, or visible contamination such as cloudiness or algae. If any of these are present, it's best to discard the water.