This is why the water on your nightstand tastes weird in the morning

If you’re among the majority of people who’ve been told to “drink more water,” then you probably have a glass filled with H20 on your nightstand right now. Since this is one of the first places you see before you fall asleep and after you wake up, nightstand water can effortlessly remind you to drink more fluids. However… such fluids don’t always taste great after sitting out overnight and Science is to blame.

When it comes to water that seems stale, SciShow reports that several factors may be involved. Firstly, it’s important to note that water isn’t only made up of H20 molecules – it also contains plenty of other molecules and ions that can alter the taste of plain, old water.

Specifically, carbon dioxide can become one with your glass of water. We exhale this gas and it’s also what makes our beloved oceans more acidic. Interestingly enough, according to Smithsonian, carbon dioxide can have the same effect on our water-filled cups (because, if you really think about it, a glass of water is like a super mini ocean). When C02 from the surrounding air makes its way into our water, it blends with H20 molecules to form carbonic acid. This makes the water more acidic and, thus, less refreshing.

Aside from C02 entering the water, another gas leaving the water may also change the taste of our thirst-quenching drink. Since the EPA reports that many water treatment facilities add compounds containing chlorine to our water – seeing that this element is an expert at destroying bacteria and viruses – it can impact the taste of the water we get out of our faucet.

Because we’re used to drinking water with a hint of chlorine, we can begin to associate chlorine with clean water. Over time, as water sits out in the open air, the chlorine will evaporate into the air. Then, when we go to drink this water, it doesn’t taste as fresh as it did before.

Lastly, we have temperature. When you pour yourself a cool glass of water and then drink it, the cold temperature can suppress your sense of taste. In other words, when you drink cold water, you aren’t always tasting all the understated flavors that are a part of it. Alternatively, there’s warm water, which has faster moving molecules that amplify what you taste with your taste buds.

Yet, despite all these changes that happen to our water without us even knowing it, Dr. Kellogg Schwab told Time that water sitting out overnight isn’t bad for us. It may not taste like it deserves five stars, but it shouldn’t harm you in any way.