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Is It Safe to Drink Water That Has Been Sitting Overnight?

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Pentair Water Solutions
Pentair Water Solutions


Is It Safe to Drink Water That Has Been Sitting Overnight?

How long is water safe to drink after it has been sitting out? You may have asked yourself this before while clutching an old bottle of water you found in the backseat of your car from three months ago. Don't be ashamed. We've all done it.

Knowing when your water is too old to drink can help you make the right decision so you don't drink something you shouldn't.

What is Old or Stale Water?

Can water go stale? You might laugh. But it's a legitimate question.
That stale taste you get when you drink water that's been sitting in a glass overnight isn't in your head. It's a phenomenon that occurs when the chlorine in tap water evaporates.

Municipal water authorities commonly use chlorine in tap water. It helps reduce bacteria growth in water. While most people don't notice the taste, some do. So after about 12 hours of sitting and your water suddenly doesn't have any chlorine, it has a different flavor. What you taste is an absence of treatment chemicals you’re accustomed to.

A lack of chlorine on its own isn't a problem. But with other contaminants floating around, it could be. The longer you leave a glass of water on a table, the more debris - like dust - it collects. And there's also surface scum…even if you can't see it, it could introduce bacteria and other pathogens into the mix. Not fun.

Just how big of a party foul is it to drink old water? Let's take a look at two examples.

Leaving Water Out Overnight

It's unavoidable. Backwash. Even the most careful of sippers are bound to get some spit back in their water. That's life. When you take a drink, leave backwash, and let the water sit overnight… what happens?

Over hours, bacteria from your mouth can incubate. But here's the kicker. If the bacteria came from your mouth, chances are it won't cause any problems. After all, that bacteria is already present in your body.

However, sharing water with someone else? That's a big no-no. They may have different bacteria present, which could make you ill.

Even so, experts think that leaving water out overnight generally isn't too big a risk. Hydrate with happiness.


Water Bottles Left in Cars

Leaving a half-consumed water bottle in a car is another story.

There are two big things at play here: heat and plastic. Bacteria love sunbathing, so to speak. They happily reproduce in temperatures anywhere from 40 degrees Fahrenheit to 140 degrees Fahrenheit. So when your car heats up in the afternoon sun? Hello, growth spurt.

One study tested to see how quickly bacteria grew in a bottle of water. The bacteria count went from 1 colony per milliliter to 38,000 colonies per milliliter over a 48-hour period. Tap water fared much better, with less than 100 colonies per milliliter during the same span.

And don't forget about bisphenol-A. You might know it better as BPA. It's what plastic bottles are made of. When left in the sun, this industrial chemical seeps into the water, meaning you're at risk of consuming it. This is true even with unopened water bottles left in the car. Unfortunately, BPA is linked to health problems affecting the brain and other organs.

So, can you keep water bottles in the car? It's best not to.


Keep Your Water Pure with Pentair

The bottom line? Don’t leave water bottles out in the sun. And finish your glass of water when you pour it. Simple, right?

For water you can trust, try Pentair water filtration systems. Our industry-leading whole-home filtration systems offer you great-tasting water in every room of your house. Or, for trusted water from a single source, try our point-of-need solutions. Either way, you'll enjoy water you can count on. Anytime. Insist on Pentair.

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Disclaimer: The information on this website has not been reviewed by the FDA. Products offered for sale herein are not intended to treat, cure or prevent any disease or health condition. No medical claims are being made or implied. Contaminants mentioned are not necessarily in your water.

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