Quick Answer:
Cloudy or milky water after boiling is usually tiny air bubbles or minerals that come out of solution when water is heated. In many cases it clears on its own after a minute. Do a few simple checks at home — and if the cloudiness doesn’t clear, shows white residue, or affects more than one fixture, have a plumber test the source safely.
Why This Happens
Boiling changes water temperature and pressure, which can cause dissolved gases to come out as microscopic bubbles. Hard water (calcium and magnesium) can also form tiny mineral particles that make boiled water look cloudy or leave a fine white residue. Changes to filtration, pressure devices, or recent plumbing work can make these signs appear suddenly; for example, if you recently replaced a filter see Cloudy water after replacing filter, or if a pressure-reducing valve was installed see Cloudy water after installing PRV.
Step-by-Step What to Do
Do a simple glass test
- Fill a clear glass with the cloudy water and set it on a light background.
- Watch for about one minute. If the cloudiness rises from the bottom and the water clears, that’s almost always tiny air bubbles.
Compare hot and cold taps
- Fill two glasses at the same sink — one from the cold tap and one from the hot tap.
- If only the hot tap is cloudy, the source is likely the water heater or a hot line; if both are cloudy, the issue is likely in the incoming supply or a recent change to filtration or plumbing.
Check aerators and fixtures
- Unscrew the faucet aerator and look for white specks or mineral flakes trapped inside.
- Rinse the aerator and see if that clears the issue at that fixture.
Test other fixtures
- Try the kitchen sink, another bathroom sink, and an outside faucet if safe to do so. Multiple affected fixtures point to a system issue rather than one faucet.
Collect a sample and observe residue
- If you find white residue on cups, kettle bottoms, or inside the glass after evaporation, that suggests mineral deposits rather than air.
- Keep a sample of both a cloudy and a clear glass to show a plumber if needed.
What Not to Do
- Don’t assume all cloudiness is harmless air — some cases indicate mineral buildup or other problems.
- Don’t start flushing the water heater repeatedly as your first response; repeated, aggressive flushing can cause other problems if done incorrectly.
- If cloudiness persists, leaves residue, or affects multiple fixtures, have a plumber inspect and test the system rather than guessing at a fix yourself.
When to Call a Professional
Call a licensed plumber if any of the following apply:
- The cloudiness does not clear after the glass test or persists for days.
- Multiple fixtures show the same milky appearance.
- White residue remains after evaporation or you see mineral deposits on appliances.
- You notice unusual tastes, odors, or discoloration in addition to cloudiness.
A plumber can take safe water samples, test for minerals, air, and contaminants, and locate whether the issue is in the supply, water heater, or plumbing fixtures.
Safety Notes
- Do not drink water that looks contaminated or has an unusual smell until the cause is known.
- When collecting a sample, let hot water cool to a safe temperature before handling.
- Avoid using strong chemicals to “fix” cloudy water; improper chemical use can create hazards and complicate testing.
Common Homeowner Questions
- Is it dangerous to drink cloudy boiled water? If the cloudiness is only tiny air bubbles it’s not dangerous, but if it leaves residue or has odd taste or smell, avoid drinking and get it checked.
- Will the problem go away on its own? Air-related cloudiness often clears quickly; mineral-related cloudiness may persist until treated or inspected.
- Can I test this myself? Yes — use the glass test, compare hot vs cold, and inspect aerators; for persistent issues get a professional test.