Cloudy water from the tap: the glass test that tells you what it is
Milky water is common and usually harmless. A clear glass and two minutes will show you which kind you have.
Cloudy water from the tap is most often tiny air bubbles. If the glass clears from the bottom up, it is air, and it is harmless. If it stays cloudy, something else is in the water.
Fill a clear glass and put it on the bench. Watch it for a minute or two.
Clears from the bottom up: trapped air
Water under pressure holds dissolved air. When it leaves the tap the pressure drops and the air forms bubbles. They rise and the water goes clear, starting at the bottom.
This happens more in cold weather, after work on the mains or when a tap has just been fitted. It usually settles on its own within a day or two.
Stays cloudy or settles at the bottom: particles
If the water stays milky, or a fine layer settles at the bottom of the glass, it carries particles. The cause is one of a few things.
- Disturbed sediment in the mains. Works, a burst main or flushing can lift it. Ask neighbours and check with your water authority.
- Scale or minerals. Hard water can look cloudy, especially when hot. See our water hardness test.
- Your own pipes or a worn washer. If one tap is cloudy and the others are clear, the fault is local to that tap.
Only the hot tap cloudy
If cold is clear and hot is cloudy, look at the hot water system. Mineral build-up inside the tank is a common cause. Do not open the system yourself. A licensed plumber can flush and inspect it.
Tank, bore or dam water
Cloudy tank, bore or dam water needs more care. Cloudiness can mean organic matter or contamination, and you cannot judge safety by eye. Treat it as not for drinking until a laboratory has tested it. Start with non-potable water.
When to ask for help
Call your water authority if the water stays cloudy for more than a day or two, or if neighbours see it too. Call a licensed plumber if only your property is affected and flushing does not help.
What your glass test result means
Fill a clear glass and watch it for a minute or two. Match what you see to this table.
| What you see | Likely cause | What to do |
|---|---|---|
| Clears from the bottom up | Trapped air | Nothing. It is harmless and usually settles within a day or two |
| Stays milky | Particles in the water | Ask neighbours and check with your water authority |
| A fine layer settles at the bottom | Sediment, often from works or flushing in the mains | Ask your water authority about recent works |
| Cloudy and worse when hot | Scale or minerals | Check hardness with the water hardness test |
| One tap cloudy, others clear | A local fault such as a worn washer | Call a licensed plumber |
| Only the hot tap cloudy | Mineral build-up or sediment in the hot water system | Do not open it. Call a licensed plumber |
Cloudy tank, bore or dam water is different, because you cannot judge safety by eye. Treat it as not for drinking until a laboratory has tested it. The water hardness test guide shows how to check scale.
What to note before you ring your water authority
A clear report gets a faster answer. Keep a short log for a day or two.
- Which taps. Say whether it is every tap or just one, and whether it is hot, cold or both.
- The glass test. Say whether it cleared from the bottom up or stayed cloudy.
- Timing. Write down when it started, and whether it comes and goes with the time of day.
- Recent works. Note any mains work or tap fitting nearby, since both can disturb the water.
- The neighbours. Ask whether they see it too. That separates a supply problem from your own pipes.
- Your water source. Say if you use tank, bore or dam water, because the advice changes.
Call your water authority if the water stays cloudy for more than a day or two, or if neighbours see it too. Call a licensed plumber if only your property is affected and flushing does not help.
Frequently asked questions
Is cloudy tap water safe to drink?
If it clears from the bottom up, it is trapped air and harmless. If it stays cloudy, do not drink it until you know the cause. Ask your water authority.
Why is my water cloudy and then clear?
Dissolved air comes out of the water as bubbles when the pressure drops. The bubbles rise and the water clears.
Why is only my hot water cloudy?
Dissolved minerals can come out of solution when water is heated, or the hot water system may hold sediment. A licensed plumber can check it.
How long should cloudy water last?
Air-related cloudiness usually passes within a day or two. If it lasts longer, contact your water authority or a licensed plumber.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NHMRC. Australian Drinking Water Guidelines
- Sydney Water. Water supply, wastewater and stormwater services