You fill a glass in your St. Louis kitchen and the water looks milky, like it has a faint haze in it. That can be alarming, but cloudy water is often harmless. The trick is to figure out what is making it cloudy before you decide what to do next.

What Cloudiness Usually Means

In most homes, cloudy water comes from one of three sources.

  • Dissolved air. Water under pressure in the pipes holds air in solution. When it leaves the faucet and warms up in a glass, tiny bubbles come out and make it look milky. This is the most common cause and it is not a sign of contamination.
  • Fine mineral particles. Some minerals can come out of solution and form tiny particles that stay suspended for a while. These may settle or cling to the glass.
  • Sediment or debris. Work on the main line, a valve change, or a disturbed pipe can stir up loose material. This usually shows up at one or more faucets and may come with grit, flakes, or a change in color.

Step One: The Glass Test

Start with the simplest check. It takes only a few minutes and needs nothing but a clear glass.

  1. Run the cold tap for a short time, then fill a clear glass with cold water.
  2. Set the glass on a counter where you can see it clearly and leave it alone.
  3. Watch the glass for several minutes. Look at the bottom, the sides, and the surface.
  4. Note whether the cloudiness clears from the top down, clears from the bottom up, or stays the same.

If small bubbles rise and the water clears steadily from the top or sides, you are most likely looking at dissolved air. If the haze stays put, or fine particles collect on the bottom or sides, the cause is more likely minerals or sediment.

Step Two: Check Where the Cloudiness Shows Up

Next, find out whether the problem is in one place or the whole house. Walk through each fixture and do the same glass test.

  1. Test the cold kitchen tap, then the cold bathroom tap farthest from the water entry point.
  2. Test the hot tap at the same fixtures. Hot water comes from the water heater, so a difference between hot and cold can point to the heater or its piping.
  3. Check an outdoor hose bib if you have one, since it sits at a different point on the line.
  4. Remove and rinse the aerator on the faucet with the most cloudiness, then test again. Debris trapped in an aerator can make the water look different at only one spot.

If every tap in the house shows the same haze and it clears in the glass, air is the likely cause. If only one fixture is affected, the problem is probably local, such as its aerator or a supply line to that fixture.

Clues That Point Toward Air

  • The water clears within a few minutes.
  • Bubbles rise in the glass.
  • The cloudiness is worse after a cold morning or after the utility has done work nearby.
  • The water runs clear after you let the tap run for a longer time.

Clues That Point Toward Particles or Sediment

  • The haze does not clear after several minutes.
  • You see grit, flakes, or fine powder in the glass or on the aerator.
  • Only some taps are affected, or the problem comes and goes over days.
  • The water changes color, such as turning yellow, brown, or gray, or gives off an unusual smell.

Color, smell, and taste changes do not tell you what is in the water. They are reasons to stop guessing and move to a proper test.

When to Send a Sample to a Lab

If the cloudiness lasts more than a day, appears at several fixtures, or comes with color or smell changes, collect a sample and have it tested. A certified lab can measure turbidity, which is the technical term for cloudiness, and can test for specific substances such as iron, hardness, and other parameters. Ask the lab which tests fit your situation, and follow its instructions for collecting the sample so the results mean something.

If anyone in the home has questions about whether the water is safe to drink, contact your water provider and a state-certified lab. A basic glass test cannot answer that question on its own.

Keep a Simple Record

A short log makes it easier to spot patterns. For each episode, write down the date, the time, the fixture you tested, whether the water was cold or hot, and whether it cleared in the glass. If you see the same pattern after cold weather or after nearby street work in your St. Louis neighborhood, that detail can help you or a tester narrow the cause.

Questions to Answer Before You Decide

  • Does the haze clear within minutes in a glass?
  • Is it at one fixture or throughout the house?
  • Does it show up in both hot and cold water?
  • Did the problem start after work on the line or a cold snap?
  • Are there color, smell, or taste changes?

If most answers point toward air and the water clears steadily, you probably have nothing to fix beyond waiting a bit. If the answers point toward particles, color, or changes across the house, collect a sample and test it. Cloudy water in St. Louis is common, and a few careful checks will usually tell you which path to take.