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


Is It Safe to Drink Water That Has Been Sitting Overnight?A few years ago we delved into the science behind stale water that’s been in a glass overnight. No doubt you’ve woken up in the morning and downed a glass on a nearby end table or countertop, but often it doesn’t taste as “fresh” as it did when you poured it.

The change in taste for water that has sat in a glass for many an hour is attributed to the lack of chlorine. Most municipal water is treated with chlorine for sanitation and cleanliness. Chlorine is quick to evaporate, so once you get around to drinking that room temperature glass of water there’s no longer chlorine inside. What you taste is an absence of treatment chemicals you’re accustomed to.

Beyond the change in taste, though, you may have never asked yourself: is it safe to drink water that has been sitting in a glass for eight hours? For two days? At what point is that glass of water no longer considered safe to consume?

That depends on a variety of factors. The longer you leave a glass of water on a table the more debris like dust it will be exposed to. Surface scum on your glass, especially when it’s visible to the naked eye, could carry a combination of pathogens or microorganisms that could make you sick. Do you have a bug problem in your home? Yet another reason not to drink water that has sat out for too long.

The biggest threat to someone’s health is actually the backwash that escapes our mouth and nose when we take a few sips of a glass and leave it unfinished. Even in water bottles this “backwash” can introduce bacteria into the water in your glass. Over hours this bacteria can incubate.

However, it’s important to note that your own bacteria generally won’t make you “sick.” However, you should never share water with someone, as their bacteria could make you fall ill. If a family member or spouse drinks a portion of a glass of water, don’t finish it off for them the next day. At that point microorganisms from their saliva have had time to spread and grow throughout the glass.

The more dangerous form of “leaving a glass out overnight” is leaving a plastic water bottle in your car and consuming it later. Heated water is the perfect environment for bacteria to grow, especially if you’ve already taken a swig.

Unopened water bottles are still unsafe to drink once they’ve been left out in the sun. Many brands of water bottles contain BPA and similar chemicals that have been linked to health problems affecting the brain and other organs. BPA can leach into the water while the bottle is being heated, causing transference of unwanted chemicals.

So, what’s the bottom line? Don’t leave water bottles out in the sun. If you can, finish a glass of water when you pour it, and don’t leave it for the next day. If you do end up drinking a glass of water the day after you poured it, only drink water that’s yours! Sharing a glass is far more likely to cause an issue.

No matter when you consume your glass of water, keep it as fresh and clean as you can by drinking pure filtered water. Pelican Water makes the process of choosing a water filtration system easier than ever – call us today to learn more.

Pelican Combo System Salt-Free Water Softener Whole-House Water Filter