Problems you can see
Why your tap water looks cloudy or milky
There is a simple test that separates the harmless explanation from the ones worth acting on, and it takes about two minutes.
The short version: cloudy water is almost always dissolved air. Millions of tiny bubbles come out of solution when pressurized water reaches your tap, and they scatter light.
Fill a clear glass and watch it. If the cloudiness clears from the bottom upward within a few minutes, it is air and it is harmless. If it clears from the top down, or does not clear at all, it is suspended solids and worth looking into.
The two-minute test
Fill a clear glass from the cold tap and set it on a counter without stirring it. Watch the direction the cloudiness disappears.
| What you see | What it is | What to do |
|---|---|---|
| Clears from the bottom up, 1-3 minutes | Dissolved air | Nothing. It is harmless. |
| Clears from the top down, particles settle | Sediment or rust | Flush the line; call the utility if it persists |
| Stays uniformly cloudy | Fine suspended solids | Contact your utility |
| Only the hot tap is affected | Water heater | Have the heater inspected |
Air rises, so bubbles clear upward and the glass becomes clear from the bottom. Solids sink, so a glass with sediment clears from the top. That difference tells you almost everything.
Why air ends up in the water
Water in a distribution main is under pressure, and pressurized water holds more dissolved gas. When it leaves your faucet at atmospheric pressure, that gas comes out of solution as microbubbles — the same thing that happens when a carbonated bottle is opened, at a much smaller scale.
It is more noticeable in a few situations. Cold water holds more dissolved gas than warm, so milky water is a winter phenomenon in much of the country. Work on a water main introduces air into the system, and it can take days to clear. Aerators on modern faucets deliberately mix air into the stream. None of these indicates a problem.
When cloudiness means something else
Persistent cloudiness that does not clear is suspended material, and the cause matters.
- Rust and sediment from aging iron mains, often after a pressure change, hydrant flushing or a repair. Usually accompanied by a brown or yellow tint.
- Hardness precipitate, a fine white haze of calcium carbonate in very hard water, more visible in hot water and alongside scale on fixtures.
- Water heater problems if only the hot tap is cloudy: a deteriorating anode rod or accumulated sediment in the tank.
- A break in the main, which can draw in outside material. This is the one case that warrants a prompt call, and utilities issue boil notices when it applies.
What cloudiness does not tell you
This is the part worth being clear about. Clarity is a poor guide to safety in either direction.
Cloudy water from dissolved air is perfectly safe. And perfectly clear water can contain lead, nitrate, arsenic or PFAS at levels well above federal limits, because none of those are visible at any concentration. PFAS is measured in parts per trillion; nothing you can see operates at that scale.
If your concern is what is dissolved in the water rather than what is suspended in it, the federal test results for your system are the place to start, and your annual water quality report covers the contaminants that testing did not.
When to call your utility
- Cloudiness that has not cleared after several days of normal use
- Water that stays cloudy after standing for ten minutes
- Cloudiness accompanied by an unusual smell, taste or color
- A sudden change with no preceding work in the street
- Any cloudiness alongside a drop in pressure, which can indicate a main break
Utilities generally want these calls. A cluster of reports from one street is often how a localized problem is first identified.
See what federal testing found in your own water system
Check your ZIP codeSources
- US EPA, Drinking Water Requirements for States and Public Water Systems.
- US EPA, National Primary Drinking Water Regulations.