No, pure water itself does not expire in the way food or perishable items do. Water (H₂O) is a chemically stable compound that doesn’t spoil, grow bacteria on its own, or break down over time under normal conditions.
However, the answer depends on the context:
Tap water or stored water in clean containers — If it’s properly treated and stored (e.g., in a sealed, food-grade container away from contaminants), it can last indefinitely without “expiring.” The main risks come from external contamination, like algae growth if exposed to light, or bacterial introduction if the container isn’t clean.
Bottled water — This is where expiration dates often appear (usually “best by” dates around 1–2 years). The FDA (U.S. Food and Drug Administration) does not require expiration dates on bottled water and states it has an indefinite shelf life when unopened and properly produced/stored. Water doesn’t go bad, but the plastic bottle can degrade over time:
Plastic (like PET or HDPE) is slightly porous and can leach very small amounts of chemicals (e.g., antimony) into the water, especially if stored in heat, direct sunlight, or for many years.
The water might develop off-tastes or odors from absorbing external smells through the plastic or from minor chemical leaching.
Manufacturers add dates for practical reasons: inventory rotation, compliance with some older state laws (like a past New Jersey rule), or to match bottling lines used for other beverages.
In practice:
Unopened bottled water stored in cool, dark conditions is generally safe to drink well past the printed date — it just might not taste as fresh.
Opened bottled water should be consumed within days (typically 3–7 days recommended) because once exposed to air and your mouth, bacteria from the environment or backwash can grow.
Bottom line — Water doesn’t expire chemically, but packaging, storage conditions, and contamination risks can affect its quality and safety over long periods. For emergency storage or long-term use, glass containers or high-quality metal ones often preserve water better than plastic.