It’s actually quite common for water to look cloudy or milky; this is not caused by anything harmful, but is due to the fact it contains tiny bubbles of air. These air bubbles are always present in water, but it can be more obvious if it has just travelled through the mains.
It can also mean there’s a burst mains pipe, or a faulty plumbing fitting has been used. You may even notice banging or knocking noises that sound like they’re coming from the internal plumbing whilst running your taps, making this more likely.
You can check if the cloudy appearance is a problem by filling a glass of water and leaving it to stand for a minute or two. You can expect to see the water becoming clearer from the bottom to the top.
A potential fix for cloudy water is to try running the cold water tap at the first point of entry (closest to the internal stop tap) on a slow, steady flow. Whilst the tap is running, turn the internal stop tap on/off around 4-6 times in order to release air from the pipes (source: WaterSafe).
Cloudy or milky water should be safe to drink, but if you’re still concerned or would like more advice, contact your local water supplier.