The water that comes out of your tap has existed on Earth as a solid, liquid, or gas for about as long as the planet is old. Just about every living organism today consumes and expels water to survive, and while it can be contaminated, or the 2 hydrogen and 1 oxygen molecules (H2O) separated and put back together, at no point will anyone complain about expired water.
That’s not to say you won’t find an expiration date on your bottle of water. At one time a New Jersey law did require that companies use an expiration dates on bottled water products, despite the FDA stating there is no scientific reason to do so. Today some companies still do this to help control stock. Stores may pull unsold cases of water after a few years due to quality concerns. Water can leach plastic flavors, or if there are minerals added or naturally present, they may settle and cause unsightly granules that people won’t want to see floating in the water.
That begs the question: If water doesn’t expire, why does water that sits out in a glass overnight taste or look different?
A few different things are happening with your drinking water. If you take a glass and fill it with tap water you might find there are a few unwelcome flavors, though it is still safe to drink. The big reason for bad tastes right from the faucet is chlorine used to disinfect the water, but because water normally travels through underground pipes that are cooler than the air at ground level, the flavor pallet is diminished. The same happens when you add ice or if you keep a Brita pitcher in the fridge. As the water sits out and warms, your senses begin to pick up a more complete profile of flavors. After a day or so, due to exposure to sunlight, particles in the air, various gases, and changes to acidity, a different appearance and tastes become stronger.
Due to bottled water being sealed, even if you leave it out at room temperature for years, the tastes probably won’t change very much from the original source of water. Once you break the seal expect the water to begin a slow transformation depending on how long the cap was left off. But you probably won’t want to keep the water around too long. Even though water doesn’t expire chlorine does evaporate. This leaves room for microorganisms that are in your mouth, on the glass, your faucet, or floating around the air and will quickly multiply in your open bottle or half-empty glass. Unlike juices or sodas, or foods that contain sugars or other elements that feeds the growth of mold, water will continue to look clear despite the likelihood of potentially harmful bacteria forming after 48 hours.
When storing bottled water or other emergency supplies there are a few precautions to take. Always keep water, food stuffs, and medicine in a dark, cool place where it won’t come into contact with animals or accidentally become damaged. You probably should not bottle your own water unless you know how to do so safely. While bottled water isn’t environmentally safe and can contain many contaminants, there is a much lower risk to coming into contact with microorganisms. There are many ways to ensure your water is free of most contaminants and bacteria including Reverse Osmosis, Ultraviolet, and NSF 53-rated water filters.
Marianne says
Yes, plastic bottles makes water unusable with time.
Eric Mazzoni says
You are right. The jury is still out on the long-term, or even short-term impact of drinking from inexpensive plastic containers. Especially when that plastic is subject to warm temperatures and sunlight. Unfortunately people love the convenience of bottled water despite the cost and harsh environmental impact, and more-so that the water often comes from municipal sources and only goes through a basic filtration process. It may take another few decades before we begin to understand how the rise in popularity and use of bottled water affects people’s health.
We wish more people would buy reusable bottles that uses higher quality food safe plastics and filling that with water that has passed through a Brita or Zero Water pitcher, or filter on your tap. You will save money in the long-term and reduce the risk of exposure to a number of different chemicals.
Steven Sedlmayr says
I agree with Phillip, however, another caveat, is that bottled water in plastic leaches faster at higher temperatures. You never know where the water sat on a dock, and hot it was. And though they have BPA out of most plastic bottled waters, the are using PBS and other that have not been tested and are just as bad as BPA. And what leaches from the bottle disrupts the endocrine and hormone systems of most people. It can even make digestion hard.
Phillip Brandt says
Unless water is bottled in glass, it picks up contaminants from its plastic container relatively quickly. Bottled water over 1 week old has a taste of chemicals released from the ‘bottle’, and these contaminants have been shown to be carcinogenic. The FDA has advised not drinking bottled water that has been in an parked auto’s heat. The advisory has nothing to do with bacteria, but instead, the contamination from the bottle. And by the way, clean water does not have enough nutrients in it to support bacterial growth to any dangerous extent.