You’ve done it. Don’t deny it. We all have. You’ve left a glass of water on your nightstand with every intention of drinking it before you went to sleep. But then life happened and you forgot. Now it’s 7 a.m. and there’s the glass still sitting there on your nightstand. You find yourself staring at it, pondering a very low-stakes but surprisingly philosophical question: Can I still drink that? Or has some contamination taken hold in there overnight?
Water, the simplest and most necessary thing we consume—nope, even it has limits. I don’t mean the dramatic ticking time bomb of safety limits, but everyone’s gone through the “Yummy or Gross” stage of Lee Williamson’s 2009 TED statement, when that once-fresh H2O starts to feel a little, well, questionable.
So how long can you leave water sitting there before it goes weird? In short, it depends. (It always depends.)
First, water never goes bad, But Everything Needs a Cleaning Once in a While
Let’s be clear: water—like, pure, distilled, nothing but H2O water—doesn’t spoil. It doesn’t go bad like milk does. But just because it doesn’t spoil or have an end date doesn’t mean it’s everlasting. What changes over time is the nature of the environment surrounding it: air, container, temperature, and all the microscopic nonsense that is floating around waiting to take advantage of a stagnant pool.
Allowing water to sit for an extended period of time leaves the bucket of water susceptible to spores, bacteria, dust, and everything that is floaty in the air you can’t see, and probably don’t want in your mouth, particularly when it’s been in contact with air for an extended amount of time.
So sorry, grab another cup. Water itself doesn’t technically spoil. It can turn into a slightly questionable-smelling science experiment when you leave it long enough.
So Wait A Minute, How Long Can Water Go Sitting in a Container?
Here’s the good news: if you’re storing it correctly—meaning clean water in a clean sealed container—you can keep it for quite a while. We’re talking months. In fact, FEMA and the CDC both even say that stored tap water in food grade containers when preparing for an emergency could last for 6 months, perhaps even a year when well maintained.
But there are a few rules:
Food grade containers. Glass or BPA-free plastic work well.
Seal tightly. No air—seriously—air is the enemy.
Keep it cool, and dark. Light and heat break down water quality over time, and if any sort of contamination exists, light and heat encourages growth of algae or bacteria.
So yes, you can’t just throw a gallon of tap water into an old milk jug and leave that jug up next to a sunny window and expect it to be good next July. That’s not storage, that’s not good.
And What About That Sad Glass on Your Nightstand?
Okay, back to the real issue. The little water glass you’ve forgotten. How long has it been there? Eight hours? Twelve? Two days?
If it’s just been sitting out overnight in a clean glass and your cat hasn’t been drinking from it (or worse), it’s most likely still fine. Water doesn’t turn into a bacteria petri dish in six hours. Most of the danger comes from exposure: outdoor air, dust, insects, and etc. Things that are in the environment and being brought into your home.
You should consider the glassware. If the glass is a little dirty (maybe you just grabbed it from the drying rack without looking), or if it’s somewhere there is a lot of airflow (hey kitchen counter), it has higher chances of having some unwelcome hitchhikers.
Honestly, if the water appears clear, has no odor and doesn’t taste like dirt or dust? You probably have very low risk if you take a sip. If you find yourself staring at it and saying “Hmm…” for over five seconds? You are probably better off just pouring a new glass. It is water. You’re not breaking the bank.
Storage Tips for Water Long Term
(If you like having a ‘glorified’ emergency kit, or are bored, or just organized)
If you’re the type of person who likes to be prepared for emergencies (emergency kits, camping gear, backup plans for your backup plans), storing water well, is an art form in and of itself. Here’s my advice:
Select high quality or appropriate containers.
This is not just an old juice bottle you rinsed out. Be as safe as possible and use containers that say they are food-safe (never take risks with humans). Plastic with #1, #2, or #4 probably are ok, or just go with glass jugs that have secure lids.
Store dark and dry
Your water shelf life will be greatly improved if you store it dark and dry – closets, basements, under the bed – anything without windows or heat vents. Mark and rotate
Be sure to mark the date that you have filled it and please don’t let it sit there for years without being opened. Approximately every 6 months swap it out—use the previous batch and fill it back up with fresh water. You will always have a fresh supply.
If the Water is Suspicious, Purify
If the water is questionable or you are possibly going to store it for an extended period of time, purification tablets or drops were made for these situations. Some people even boil the water prior to sealing it in a container, just to play it safe.
But…what about bottled water?
Bottled water is slightly different. It will have an expiration date printed on the label, which is really for the bottle itself, rather than the actual water. Plastic will leach into the water, over time, especially if they’ve been held in the heat for a while. The water inside is technically still ok, but the taste can start to get, I don’t know, sort of plasticky. It’s gross. So, just stick to community practices on the label and store somewhere cool. Don’t ever leave it in your car. Please.
Trust Experience (It normally knows)
At the end of the day, your body is likely pretty good at knowing when there’s something wrong. If your water is cloudy or smells strange or tastes like it has been skunked in the garage since 2009 it isn’t worth the risk. Toss it. Start again. You’re not in a desert. You can get a clean cup and turn on a tap.
How long can water store?
Short version:
Sealed and clean? 6-12 months
Opened and exposed? A few hours to maybe a maximum of day or two.
Sketchy container? Don’t chance it
Looks/smells/tastes weird? Don’t overthink it. Just get fresh water.
It’s one of the easiest things in the world to get a replacement, and one of verging on worst thing you can mess up. So yes, Drink Up –but maybe just rinse the cup first.
