Cloudy, Brown, or Discolored Tap Water: What It Means and What to Do

Cloudy or milky white tap water is almost always tiny air bubbles, and it is harmless: pour a glass, wait a minute or two, and it should clear from the bottom up. Brown, red, orange or yellow water usually comes from iron and other sediment that got stirred up in the water mains, or from rust in your own pipes or water heater. It is usually not a health emergency, but you shouldn’t drink obviously discolored water. Run the cold tap until it clears, and call your utility if it doesn’t.

Below is how to figure out which situation you have and what to do about it.

Cloudy or milky white water: the glass test

What it usually is: Dissolved air. Water in the mains is under pressure, and that pressure holds extra air in the water. When it comes out of your faucet, the pressure drops and the air forms tiny bubbles that make the water look white or milky. New York City’s water department notes that cloudiness clears once the water sits in a glass and the air escapes.

The test: Fill a clear glass and set it on the counter. Washington State’s Department of Health says that if the water starts to clear at the bottom of the glass first, the cloudiness is trapped air, it is not a health threat, and it should clear in a few minutes. New York City’s water department says the same: this condition is not a public health concern. If you have a private well, Washington’s guidance notes that the pumping system may be causing it, and a qualified contractor can help.

If it doesn’t clear: Cloudiness that stays put, or that leaves a white film or crust on dishes and fixtures, may be dissolved minerals like calcium and magnesium (hard water). That’s a nuisance, not a health problem. See our explainer on hard water. If the water stays cloudy and also smells or tastes odd, contact your utility.

A different kind of “cloudy”: Utilities measure turbidity, a technical term for cloudiness caused by particles. The EPA regulates turbidity through treatment requirements because it is used to indicate water quality and how well filtration is working. If your utility issues a notice about turbidity, that’s a different situation from air bubbles. Follow the instructions in the notice exactly. Our guide to boil water advisories explains what those notices mean.

Brown, red, orange or yellow water

What it usually is: Iron, and sometimes manganese. The EPA’s secondary standards link iron to a rusty color, sediment, a metallic taste and reddish or orange staining. These are aesthetic guidelines, not health limits. Washington State’s health department puts it directly: while unpleasant and potentially damaging to clothes and fixtures, iron in drinking water is not a human health concern.

The key question is whether the color showed up suddenly or has been there for a while.

Sudden brown water (the whole house, often the neighbors too)

This usually means something disturbed the water mains. New York City’s water department lists water main breaks, repairs, construction and fire hydrant use as common triggers, and says the discoloration is a temporary condition most often from iron and manganese particles. Because the mains are pressurized, sudden changes in flow stir up sediment that had settled inside the pipes.

What to do:

Don’t drink it while it’s discolored. NYC’s water department puts it plainly: while it is not harmful, residents should not drink obviously discolored water.
Run the cold water. Washington State’s Department of Health suggests flushing all your cold-water faucets and toilets for a few minutes. If the water doesn’t clear, wait a while and try again before calling your utility. NYC’s water department says it typically resolves sudden discoloration by flushing nearby hydrants.
Avoid the hot water. Running hot taps while the water is discolored can pull sediment into your water heater.
Hold off on laundry. Washington’s health department notes that rusty water can damage clothes and fixtures, so wait until the water runs clear.
Skip filtered taps. Running sediment through a pitcher, fridge or under-sink filter can clog it.

Check for local work first. Washington’s guidance is that sudden discoloration likely means something disturbed the flow in the water main, such as a line break or firefighting. A quick look at your utility’s website or alerts, or a question to the neighbors, often explains it.

Ongoing brown or yellow water

If discoloration keeps coming back, the source is more likely closer to home.

Older iron or galvanized pipes can rust from the inside. NYC’s water department notes that ongoing brown water often comes from corroded plumbing or rusty water heaters, and suggests running cold water for 2 to 3 minutes when it hasn’t been used for a long time.
A private well with naturally high iron or manganese. This is common in some groundwater; a water test will tell you the levels. See our well water testing guide.
Low water use. Water that sits in pipes for days, such as in a vacation home, often comes out rusty at first.

If you’re on a public system and the problem persists at every tap after flushing, report it. Your utility may need to flush the main on your street.

Black or dark brown particles or stains

What it usually is: Manganese. The EPA links manganese to a black to brown color, black staining, and a bitter metallic taste, with a secondary standard of 0.05 mg/L.

Unlike iron, manganese has a health advisory. The EPA’s 2004 health advisory sets a lifetime level of 0.3 mg/L to protect against possible neurological effects, and recommends that the 0.3 mg/L level also be used for infants younger than 6 months even for short exposures. The Minnesota Department of Health recommends a lower level, 100 micrograms per liter (0.1 mg/L), for water given to infants or used to make formula.

So if you see black staining and you have a baby in the house, ask your utility for its manganese results or test a private well. Our guide on tap water for baby formula covers this in more detail.

Blue or green stains

What it usually is: Copper from your plumbing. The EPA links copper to a metallic taste and blue-green staining. Unlike iron, copper has a health-based action level of 1.3 mg/L; the EPA lists stomach upset as a short-term effect and liver or kidney damage as a long-term effect of too much copper.

Blue-green stains are a sign that water may be corroding your copper pipes. That’s worth a test, especially because the same corrosive conditions can also release lead from older plumbing. Our guide to lead in tap water explains how to test.

Discolored hot water only

If the cold water is clear but the hot water is rusty, brown or full of sediment, the problem is almost certainly your water heater, not your utility.

Sediment buildup. Minerals and rust collect at the bottom of the tank over time. The CDC notes that most water heater manufacturers recommend regular flushing, and that flushing is commonly suggested yearly, after plumbing work, or if tap water is discolored.
A corroding tank. Rusty hot water can mean the tank’s lining or anode rod is wearing out. A plumber can tell you whether it can be serviced or needs replacing.

Follow the manufacturer’s instructions when draining or flushing a water heater, and be careful: the water inside is hot. If you’re not comfortable doing it, hire a plumber.

When to stop drinking the water and call

Most discoloration is a nuisance. Washington State’s health department takes a cautious view, saying that a sudden change in water color, no matter what color, could indicate a public health concern. That’s a reasonable rule of thumb. Stop drinking the water and call your utility (or your local health department if you have a well) if:

The water stays discolored after you’ve flushed the cold taps and waited, as described above.
The color comes with a new smell or taste, especially fuel, solvent or sewage odors. See why tap water smells or tastes strange.
The color change came with a loss of water pressure or an outage. Washington’s guidance notes that sudden discoloration can mean a plumbing problem allowed unsafe water into the line.
Your utility has issued any notice. Follow it over general advice like this.

If you want to see your utility’s recent EPA compliance record, including any treatment technique or monitoring violations, search for your water system. Our methodology page explains how we grade systems.

Quick reference

What you see	Most likely cause	Health concern?	First step
Milky white, clears from bottom	Air bubbles	No	Wait a minute
Cloudy, doesn’t clear, white film	Hardness minerals	Generally no	Check hardness
Sudden brown/red/yellow	Main break, flushing, iron	Don’t drink while discolored	Run cold tap; call if it persists
Ongoing brown, worse after sitting	Rusty pipes or heater	Usually aesthetic	Flush; check plumbing
Black stains or particles	Manganese	Possible, at high levels	Ask for results or test
Blue-green stains	Copper corrosion	Possible	Test for copper and lead
Hot water only	Water heater	Usually aesthetic	Flush or service heater