Are you someone who will take a glass of water to bed sometimes? Do you ever find that when you wake up the next morning that when you reach for a sip that your water tastes a little off?

Maybe you have a bottle of water in your car and have gone to take a sip after it’s been sitting there for a few days to find something isn’t quite right about it.

Some people think that water can go bad. In this blog post, let’s talk about why people think water can go bad; what to do if your water doesn’t feel fresh and what it can mean for your supply.

Why do we think water goes bad?

It might sound quite silly, but when water goes bad, it is better to think of it like water going stale.

So, how can a liquid go stale?  Well, just like a loaf of bread that’s been sitting out too long, water in a glass that is exposed to air will see air in the glass want to escape.

You’ll usually notice this when a glass is left sitting out for a long time, and little bubbles start to appear at the top. While air is trying to get out, other gases are trying to get in.

We are talking about extremely small amounts of carbon dioxide and chemicals in the air that don’t do any harm but are noticeable when you take a drink.

can water expire

So, is it just exposure to air that makes water taste bad?

No. Not exactly. There are actually three main contributors that affect (in this specific sense) water quality:


What do we mean by contaminants? When you have a bucket of water in your garden, over time, you’ll see some dirt and insects infiltrate the water. Your water naturally ends up absorbing external materials when it is exposed. Similarly, a glass of drinking water on the bedside table will take in dust particles for example when left uncovered.


Tap water reacts in a similar fashion to a bottle of red wine or a pint of beer when it changes in temperature. Wine drinkers will open a bottle and leave it at room temperature to let it breathe. In essence, as the temperature of the wine rises to match the room, certain aromas and flavours can come out.

So, if you leave your glass of drinking water for a few hours, you’ll notice a marked difference in taste without having added anything due to temperature going up.


When you take a drink of anything, often it isn’t the taste that is the first sense to react, but your smell. Your nose will be the first to know if something is a bit awry.

Just imagine the first sip of a cup of tea with slightly dodgy milk. Often it will be your sense of smell that will send alarm bells ringing before your taste buds have reacted.

What gives bad water a different feeling on the tongue?

The carbon dioxide which gets into open water over time will ever so slightly lower the pH. It won’t be massively noticeable in the taste, but your tongue and nose will sense the difference.

Is cloudy water bad water?

No. Cloudy water isn’t a sign of anything bad happening. It’s just trapped air. You can find out more by reading our blog post on why tap water gets cloudy.

How do I get rid of bad water?

If you feel the water you drink is bad, try using a water filter to see if it improves the taste and overall quality.

Do plastic water bottles cause harm?

can bottled water go bad

Can my supply cause bad water?

Water is the most regulated substance we have in the UK, much more than any harmful chemical or product on the shelves. Water companies have to meet strict regulations and are constantly audited to ensure that the water we all use in daily life is safe to consume.

If you are concerned that you have a water quality incident, you can contact Castle Water on 01250 718 700 or use our webchat service (at the right-bottom of every page). We will gather as much information as possible about the issue and will immediately contact your water network owner to investigate.

Alternatively, you can contact your water network owner directly using the contact details provided here.

Looking for more from your business water retailer? Get in touch

Are the existing services at your current business water retailer just not up to scratch?

At Castle Water, we like to keep things simple. If your water services aren’t making sense, and you feel your current provider isn’t helping you with water issues, call us on 01250 718 700 or contact us here and we’ll see how we can help your business.