Why is my tap water cloudy or milky?

What causes cloudy tap water?

Dissolved air (most common). Water in mains pipes is under pressure. When it enters your tap and pressure drops, dissolved oxygen and nitrogen form tiny bubbles — exactly like opening a fizzy drink. This gives the water a milky, opaque appearance that clears from the bottom up as the bubbles rise. Completely harmless.

Recent maintenance work. Flushing or repair work on nearby mains can disturb air pockets in the network, temporarily increasing the dissolved air in your supply.

Cold weather. Cold water can hold more dissolved gas than warm water. In winter, water entering a warm house can appear cloudier than usual.

High mineral content (hard water areas). In very hard water areas, water can appear faintly hazy due to calcium and magnesium content. This does not clear on standing — but is harmless.

The 30-second glass test

Fill a clear glass from the cold tap and place it on a white surface. Watch carefully:

• Clears bottom-to-top within 30 seconds — dissolved air. Safe to drink.
• Stays uniformly cloudy — something else. Run tap for 2 minutes. If still cloudy after 24 hours, contact supplier.
• Has a colour (yellow, brown, grey) — stop using and contact water company immediately.

What to do

When to contact your water company

• Cloudiness does not clear after 30 seconds in the glass test
• The water has any colour tint — even faint yellow or grey
• Cloudiness persists for more than 24 hours
• Neighbours are also affected
• You have any concerns about taste or smell alongside the cloudiness