The bottle of “purified” water I got here has a stamped expiration date (“Best before 3/4/02”). The label claims less than 5 ppm dissolved solids, and that it’s [apparently tap] water put through reverse osmosis.
Why would it expire ? From picking up plastic odors from the jug ?
Maybe if you get water bottled in glass containers, with good lids it’s good indefinitely, but most I see is in plastic containers that very often don’t seal perfectly - namely the gallon-milkjug-type containers. These frequently have minute holes, especially around the seams. I’d bet that if you kept it long enough that it would grow algae eventually. - The store where I work occasionally skips the order for a day or two in order to sell out and clear the shelves; the dates on ours are 12 or 14 months, and we don’t sell them out of date. I haven’t found a jug older than about five or six months (but sometimes they reach us two months old already). - MC
That’s not a true expiration date, that’s a guidline for the store and the consumer. Plastic bottles do break down. The water you have will taste best before 3/4/02, and after that date it might taste a little more like plastic than one would want. Something that spoils easily will be marked, “Sell by …” or something similar.
In order for bacteria to breed, they have to have some source of food, usually sugar. Bacteria can’t breed in bottled water because it has no food source.
I’ll give you that there might be more living bacteria in bottled water (they won’t die in there, even if they can’t reproduce), because tap water generally has chlorine in it to kill them. However, bottled water will never have algae in it, which tap water may, along with algae by-products such as methylisobornane.
(My mother works as a chemist in a water plant. She won’t touch tap water any more, and she’s only worked there about nine months. You figure it out.)
I took a class taught by one of the Denver Metro health Districts years ago, when I worked as a Domino’s Pizza manager. There is only ONE product that is required by law to have a TRUE expiration date: Baby Formula. All others are basically marketing scams to get you to buy more often…
If you are keeping bottled water for a long time, I guess you’d want to keep it in the dark. If it has any microbes in it (i.e. it isn’t distilled), some of them can photosynthesize sugars to live on if they have light. In that case, your water could go green on you.
Still doesn’t seem like a lot of risk there, however.
OK it’s not a scam… but it’s also NOT an expiration date… it’s a ‘sell by’ date, which is put on more for the benefit of the grocer, and not for the consumer. Milk is generally still good for a few days after that date (although that’s usually the date that I start doing the ‘sniff test’)