It’s something we've all experienced. You turn the tap on, fill up a glass and as you're about to take a sip, realise there's a slight mist in the water. On inspection, there’s a swirl in your glass and the water is white in the middle. Nothing was added to the glass and you know it was clean before water was in there. So how did you end up with cloudy water?

It’s something that does happen from time to time, but thankfully it isn’t something to be worried about, whether you’re going to have a drink at home or need to use a lot of water at work.

In this short blog post, we talk about precisely what cloudy water is, why it happens, and what you can do to prevent it.

What is cloudy water?

It’s nothing but science in action! Cloudy water is caused by tiny air bubbles that end up in your water supply and cannot escape.

Have you ever noticed that sometimes when you open a bottle of still water, bubbles appear at the top? The same happens in your pipes along water’s journey. The tiny air bubbles can make their way from anywhere, straight into your glass.

What causes cloudy water in the first place?

Cloudy water shouldn’t happen because of how your system is set up. In the majority of cases, water will appear cloudy because air has somehow entered into your water system, for example, due to work being carried out on a mains pipe.

When the air is trapped, it dissolves in the water. Because water is always moving, it’s not noticeable until you pour a glass and let the water settle.

But why exactly does the water look cloudy?

It's all down to temperature. Cold water holds more air than warm water. When very cold water makes its way from your local reservoir, its temperature will rise, and some of that air will try to be released.

However, the air can't be released until you pour the water. The next time it happens, stand back and keep an eye on the cloudy part. The cloud will tend to start in the middle of your glass and slowly move up before it disappears. This is because the air is looking for the quickest way to get out, and that’s upwards.

Why would you get cloudy water on a closed system?

Some houses and business may have a private water supply but still see cloudy water from time to time. In these instances, it's all down to pressure. This is because water can hold a higher volume of air when under pressure.

Again, once the water leaves the system and enters the glass, the pressure drops, and that air appears as bubbles - which gives the cloudy appearance.


What do I do if I have cloudy water?

You don’t need to do anything. Leave the water to sit for a few minutes and you’ll see the cloudiness disappear.

In most cases, cloudy water is just passing through and should be out of your water system within a day.

Is cloudy water harmful to drink?

No, it's not. The ‘cloudy’ part is the air bubbles finally having the chance to escape.

If you normally take a glass of water to bed at night, you’ll often notice that in the morning, a few bubbles may have appeared near the surface of the water. There is always trapped air in your water; it’s just not always as noticeable as when it is cloudy.

What if the water is discoloured, rather than cloudy?

If your water is coming out of the tap with a particular hue or colour and the water is still cloudy or discoloured after your tap has been running a while, you should have this investigated by your water network owner. (more details below).

If your water is blue, green or pink, firstly, identify the cleaning products you use of this colour in your toilet or bathroom to ensure that there isn't a loop somewhere in the system and water that should be leaving, is rerouting back into your pipes.

If your water looks dirty, then there may be a problem in the water system that needs investigating. Sometimes your water might smell or taste a little off, without there being any discolouration. In times like this, it could be that you have a blockage of waste which will need cleaned out of your pipes.

Who should I contact?

If you are concerned that you have a water quality incident, you can contact Castle Water on 01250 718700 or use our webchat service at 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.