Why is my tap water cloudy or milky?

You do not need any equipment to check this at home. Fill a clear glass straight from the tap and set it on the counter. Then watch it.

If the cloudiness is air bubbles, it can clear as those bubbles rise and escape. Bottom-up clearing is consistent with that explanation. Phoenix advises that air-caused cloudiness usually clears within a few minutes when water stands. This observation does not test for harmful germs or chemicals or establish that the water is safe to drink.

If the haze persists, or particles settle, the cause may be different from air alone. A glass test does not identify the material. Ask your provider about the change and whether appropriate testing is needed instead of diagnosing minerals or contamination by appearance.

Watching a clean, clear glass can help you describe the symptom when you contact the provider. It can suggest an air-bubble explanation, but should not be used to dismiss an advisory or a sudden change.

Air gets into your water through normal, harmless physics, and a few everyday triggers make it more noticeable.

• Pressure changes. Water in the pipes sits under pressure. When it leaves the faucet and hits open air, the pressure drops and dissolved air comes out of solution as bubbles, the same way bubbles form when you open a bottle of carbonated water.
• Temperature changes. Cold water holds more dissolved air than warm water. When chilly water in the main warms up inside your home, that extra air is released as tiny bubbles. This is why the cloudiness often shows up more in cold-weather months and why it can look stronger at the cold tap.
• Recent work on the water main. Repairs, flushing or household plumbing work can change flow and introduce air or disturb sediment. Ask the provider or contractor for the actual cause and any flushing or drinking-water instructions; do not automatically wait several days because the change followed work.

Air bubbles themselves do not prove that repairs or pressure changes left the water free of contaminants. A faucet aerator may also introduce air. The CDC recommends contacting the utility or health department about a pressure drop or water change and following any resulting advice.

Use observations to describe the change to your provider. The following signs deserve attention, and current advisories apply even when the water later looks clear.

The haze does not clear after sitting. Persistent cloudiness needs a provider check. It may involve particles or another water-quality issue, but neither the cause nor safety can be established from a glass test alone. Ask whether there is a known local event and what testing, if any, is appropriate.

You see an oily film or sheen on the surface. A rainbow or oily layer is not normal and is not air. Stop using the water for drinking and contact your water provider. A persistent foul smell, a strong chemical odor, or visible color also belongs in the call-the-utility category.

The water stays white or leaves chalky spots. White scale after water dries can be a hardness symptom, but persistent haze is not the same observation. Do not label unexplained cloudiness an aesthetic issue or identify its contents solely from a chalky appearance.

Public drinking-water systems must meet applicable EPA rules, but that does not make a particular cloudy glass a reliable safety test. Review your provider’s annual report, check current notices and ask about an unexplained change. Follow an advisory even if the water looks clear.

Phoenix is worth a special note because the local water is hard, and that can produce a white look that people confuse with cloudiness. Hard water is high in dissolved calcium and magnesium. The City of Phoenix reports total hardness in the range of roughly 172 to 302 milligrams per liter (City of Phoenix, 2025 Water Quality Report), which equals about 10 to 17.6 grains per gallon. The USGS classifies water above 180 milligrams per liter as "very hard," so much of the local supply sits at the top of the hard range and into very hard.

Hardness describes dissolved calcium and magnesium; it is different from an unidentified haze. EPA’s secondary standards cover specified aesthetic and technical concerns, including total dissolved solids, pH, iron and manganese. The secondary table does not list a separate hardness, calcium or magnesium limit. White scale can be an equipment nuisance without proving that an unrelated water change is harmless.

Scale is a solid deposit left after water dries or is heated, rather than a haze that disappears as air bubbles escape. If deposits are the concern, measure the water and choose treatment for that identified issue. Do not assume a softener or conditioner diagnoses cloudiness or removes every harmful germ or chemical.

Phoenix’s 2025 report records its disinfectant residual separately from hardness. A chlorine taste or residual measurement does not by itself explain a milky appearance. For the wider provider and monitoring context, see whether Phoenix tap water is safe to drink and how hard Phoenix water is.

If a clean glass clears after standing, air bubbles are a possible explanation. Check current provider notices before deciding what to do, especially after a pressure loss or water-main repair. Clear-looking water is not a safety certificate, and a glass test does not cancel an advisory.

Contact your water provider about persistent cloudiness, an unusual oily film, a new strong odor, visible color or a sudden change. Describe whether it affects every cold tap or one location, and ask about safe use and any appropriate testing. If contamination is suspected, follow the provider’s instructions and use a known safe source for drinking until the concern is resolved. Boiling does not make water containing harmful chemicals or toxins safe.

If the water is a color instead of cloudy, see why tap water turns brown or discolored for the causes and what to do first, and whether brown or yellow tap water is safe before you drink it. Not sure if the problem is the city's or your own plumbing? Our page on whether bad water is the city's problem or yours walks through the checks.