The Surprising Truth About Whether Bottled Water Can Go Bad
Have you ever reached for a dusty bottle of water in the back of your pantry or found one rolling around under your car seat and wondered, "Can bottled water go bad?" It seems like a simple question. After all, it's just water, right? Yet, almost every bottle you buy at the store has a "best by" date stamped on the plastic.
If you’re worried about drinking "expired" water or curious if that emergency supply in your garage is still safe, you aren't alone. Many health-conscious people worry about chemical leaching, bacterial growth, and whether water truly has a shelf life. The good news is that the answer is more about the packaging than the liquid inside.
In this guide, we’ll dive deep into the science of water stability, the risks of plastic degradation, and the best ways to store your hydration supplies so they stay fresh and safe for the long haul.
Does Water Actually Expire?
Technically speaking, water does not expire. Pure $H_{2}O$ is a chemically stable molecule that doesn't contain the sugars, proteins, or fats that cause food to spoil. However, the environment and the container it sits in can definitely "go bad."
The U.S. Food and Drug Administration (FDA) does not even require an expiration date on bottled water. They consider it to have an indefinite shelf life as long as it is produced properly and kept in a sealed, unopened container. So why the dates?
Uniformity: Many bottling plants use the same machines for soda and juice, which do expire. It's easier to stamp a date on everything.
State Laws: In the past, certain states (like New Jersey) required all food and beverage products to have an expiration date. Though many of these laws have changed, the industry standard stuck.
Taste and Quality: Over time, the taste can change. While the water may be "safe," it might not be "fresh."
The Real Culprit: Plastic Degradation and Leaching
If the water itself is fine, the concern shifts to the plastic. Most commercial water is sold in PET (polyethylene terephthalate) bottles. While PET is generally safe, it is slightly porous.
When exposed to high heat or direct sunlight, the plastic can begin to break down. This process can release trace amounts of chemicals like antimony or phthalates into the liquid. This is why water left in a hot car often develops that distinct "plastic-y" or "chemical" taste.
Understanding Microplastics
Recent studies have highlighted the presence of microplastics in bottled water. These tiny particles can shed from the bottle cap or the walls of the container itself. While the long-term health effects are still being studied, it's a major reason why many people are moving toward glass or stainless steel for long-term storage.
How to Tell if Your Bottled Water is "Off"
While "expired" water usually won't make you sick, there are signs that you should probably pour it out and recycle the bottle:
Strange Smell: If the water smells like chemicals, medicine, or even a wet basement, it has likely absorbed odors from the surrounding environment through the porous plastic.
Odd Taste: A bitter or metallic flavor is a sign of chemical leaching.
Algae Growth: If a clear bottle is left in the sun, small amounts of algae can bloom, giving the water a green tint.
Cloudiness: Any floating particles or "floaties" indicate that the seal has been compromised and bacteria may have entered.
Pro Tips for Long-Term Storage
To maximize the life of your emergency water supply and ensure the highest quality, follow these storage "golden rules":
1. Keep It Dark and Cool
Sunlight and heat are the enemies of plastic. Store your cases in a basement, a cool pantry, or a climate-controlled closet. Avoid the garage or a shed where temperatures can fluctuate wildly.
2. Stay Away from Chemicals
Because plastic is slightly permeable, you should never store water near gasoline, paint thinners, or household cleaners. The water can actually "breathe in" those fumes over time.
3. Rotate Your Stock
Follow the FIFO (First In, First Out) method. Use the oldest bottles first and replace them with new ones. While the water is safe indefinitely, a two-year rotation ensures you’re always drinking the best-tasting water.
4. Once Opened, Drink Up
The moment you open a bottle, bacteria from your mouth and the air enter the water. At room temperature, these microbes can multiply quickly. Try to finish an opened bottle within 48 hours, or keep it refrigerated to slow down bacterial growth.
Comparison: Plastic vs. Glass vs. Canned Water
| Container Type | Estimated Shelf Life (Quality) | Pros | Cons |
| Plastic (PET) | 1–2 Years | Lightweight, cheap | Leaching risk, microplastics |
| Glass | Indefinite | No leaching, best taste | Heavy, breakable |
| Aluminum Cans | 30+ Years | Light-proof, highly recyclable | Expensive, potential liner issues |
Is It Safe to Drink "Expired" Water in an Emergency?
In a survival or emergency situation, safety is relative. If the choice is between dehydration and a three-year-old bottle of water that was kept in a cool, dark place, the water is almost certainly safe to drink. The FDA’s stance on indefinite shelf life means that as long as the seal is intact and there are no visible signs of contamination (like mold or cloudiness), the risk of acute illness is extremely low.
However, for your daily hydration, sticking to fresh water and utilizing a high-quality filter at home is the best way to avoid the pitfalls of plastic degradation.
Summary: Staying Hydrated and Safe
The next time you see an expiration date on a water bottle, remember that it's more of a "freshness guarantee" than a safety warning. Water doesn't spoil like milk, but it does react to its environment. By storing your bottles properly—away from heat, light, and chemicals—you can ensure that your water stays as pure as the day it was bottled.