Can water expire? How long is it safe to drink stored water. Time duration explained

Water is a vital part of daily life, yet many people wonder whether it can expire. While plain water itself does not spoil, the containers it sits in and the way it is stored play a critical role in determining its safety. Understanding the factors that affect water quality is essential to prevent potential health risks.

Why Bottled Water Has Expiration Date
Commercially bottled water is often marked with an expiration date, typically around two years from the bottling date, according to Healthline. This practice began in the 1980s in the U.S. and became a standard across the industry, although there is no federal law that currently mandates expiration dates on bottled water.

The date primarily reflects the potential for chemical leaching from plastic bottles over time, rather than the water itself going bad. Substances like antimony and bisphenol A (BPA) can slowly migrate into water from plastic containers, especially under heat, and long-term ingestion may affect gut health, immunity, and hormone balance.

How Reusable Bottles Can Turn Risky
Even if water itself does not expire, bacteria and mould can accumulate quickly once a bottle has been opened. A study in Environmental Pollution (2024) found that biofilm-forming bacteria, some resistant to multiple drugs, were present in bottled water samples.

Every sip introduces microbes into the bottle, which cling to the walls and multiply. In reusable plastic bottles, bacteria and mould can form in just a few days, creating the potential for stomach upset, diarrhoea, and other infections. Mould growth may also lead to unpleasant odours and allergic reactions in sensitive individuals.

Best Practices for Drinking Water Safety
To reduce risks associated with old water:

• Wash reusable bottles daily with hot, soapy water, and scrub all corners. Weekly vinegar or baking soda rinses can help control bacterial growth.
• Prefer stainless steel or glass containers, which resist microbial growth and do not leach chemicals.
• Store water away from heat, sunlight, and household chemicals. Avoid leaving bottles in hot cars.
• Replace worn or scratched bottles, as they can harbour more bacteria.
• Discard water immediately if it smells sour, appears slimy, has visible mould, or has been stored for more than two to three days after opening.

Water itself does not expire, but storage conditions and container types determine safety. For safe hydration, it is advisable to drink freshly poured water, clean bottles regularly, and avoid water that has been left unused for extended periods.