Why Is My Tap Water Cloudy? The Short Answer
Most of the time, cloudy or milky tap water is air. Water travels through the mains under pressure, and pressure keeps more air dissolved in it than it could hold sitting in an open glass. When it leaves the faucet, that extra air comes out as millions of tiny bubbles, and the bubbles scatter light. That's the white haze.
But air isn't the only thing that turns water cloudy, and you don't have to guess which one you've got. A clear glass and two minutes will tell you. How the water clears, or doesn't, separates air from particles, and three follow-up questions cover the rest: is it the hot tap or the cold, city water or a private well, and every tap or only a treated one?
Here's the test, then what each result means and what to do about it.
The Glass Test: One Clear Glass, Two Minutes
Fill a clear drinking glass from the cold tap in your kitchen. Set it on the counter where you can see it against a light background, and leave it alone. Don't stir it and don't hold it up to the window yet. Watch what happens over the next couple of minutes.
It clears from the bottom up
On city water, that's air. The bubbles rise, so the bottom of the glass goes clear first and the clear zone climbs toward the top until the whole glass looks normal. The U.S. Geological Survey puts it plainly: the tiny bubbles rise to the top and escape into the air, clearing up the water, and cloudy water caused by air is completely harmless.
One exception matters. On a private well, gas from the groundwater forms bubbles that rise and clear the same way. If you're on a well and the faucet also sputters, spits or gurgles, or the water fizzes, skip ahead to the well gas section before you decide it's nothing.
It stays cloudy, or something settles to the bottom
Now you're looking at particles, not gas. Bubbles leave; particles either hang in the water or sink and collect on the bottom of the glass. This is the result worth taking seriously, and it's covered in its own section below.
It only happens with hot water, or it leaves white flakes and film
Run the same test with a glass from the hot tap. If the hot water is cloudy and the cold isn't, you're looking at either gas coming out of heated water or minerals coming out of hard water. Both are explained below.
| What the glass did | Most likely cause | What it means |
|---|---|---|
| Cleared from the bottom up within a few minutes | Dissolved air | Harmless on city water. On a well, check for gas if the faucet sputters. |
| Stayed cloudy, or grit settled on the bottom | Suspended particles (turbidity) | Call your utility or test your well before drinking it. |
| Hot tap only, cold is clear | Gas released by heating, or hardness minerals | Usually not a safety issue on city water. On a well, check for gas. |
| Well water that fizzes, with a sputtering faucet | Dissolved gas, possibly methane | A ventilation and testing question. Read the well section first. |
| Only water from a filter, softener or RO faucet | The treatment system | A system issue, not your supply. |
Milky Water That Clears: Air, and Why It Shows Up
Air in tap water isn't a defect. It's physics. Water holds more dissolved air the higher its pressure and the colder it is, so the moment it leaves a pressurized pipe and starts warming in your glass, some of that air has to come out. Usually there isn't enough to notice. Two situations make it more likely:
- Cold weather. USGS says white water usually shows up when it's very cold outside, because cold water holds more air than warm water. Winter water leaves the reservoir very cold and warms on the way to your tap, so some of its air can't stay dissolved.
- Work on the mains or your plumbing. Repairs, a shutoff, or a new connection can let air into the lines. It works its way out with normal use.
The water itself hasn't changed, and the bubbles are just air. If it clears from the bottom up, you can drink it. If it bothers you, let the glass sit for a minute before you drink, or keep a pitcher in the fridge.
Cloudy Only From the Hot Tap
When only the hot water comes out cloudy, there are two usual suspects, and the glass test helps tell them apart.
Gas coming out of heated water
Heat drives dissolved gas out of water faster. The Minnesota Department of Health notes that heating speeds the release of dissolved gas, which is why a gas problem is often worse at the hot faucet. On city water that's almost always plain air, and it clears from the bottom up like any other bubble. On a private well, read the well section below before you shrug it off.
Hard water minerals
If hot water looks hazy and doesn't clear, or your kettle and glasses end up with white flakes and film, hardness is the likelier cause. According to the U.S. Geological Survey, when hard water is heated, as in a home water heater, solid deposits of calcium carbonate can form. It's the scale inside a kettle, and the same reason glasses come out of the dishwasher spotted and cloudy. It's a nuisance and an appliance problem rather than a health one. If it sounds like your house, the hard water guide covers testing and treatment.
Cloudy Water That Doesn't Clear: Particles
If the glass stays cloudy, or grit collects at the bottom, you're seeing turbidity: particles in the water, whether they stay suspended or settle out. The EPA defines turbidity as a measure of the cloudiness of water and uses it as an indicator of water quality and filtration effectiveness. Higher turbidity is often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria.
So public water systems are held to tight limits. For systems that use conventional or direct filtration, EPA says turbidity can never go higher than 1 NTU, and it has to be at or below 0.3 NTU in at least 95 percent of each month's samples. Those are limits on how well the treatment plant filters, not readings taken at your faucet, so they can't tell you what's in your glass. What they do tell you is how seriously cloudiness is treated. Water that looks visibly cloudy and stays that way is not something to shrug off.
On city water
Sudden cloudiness that won't clear usually means something stirred up the system: a main break, hydrant flushing, nearby construction, or a pressure change that knocked sediment loose. Call the number on your water bill and ask whether there's work in your area. Have four answers ready, because they're what separate a system problem from a house problem: when it started, whether it's every tap or one, whether it's hot, cold or both, and what the glass did. Follow any advisory they've issued, and if they say nothing is happening on their side, the cause may be in your own plumbing. If your water has also turned brown or yellow, the guide to reading discolored water covers that side.
On a private well
Nobody tests a private well for you. Cloudiness that appears after heavy rain, flooding, or work on the well or pump means surface water or sediment may be getting in, and that's when bacteria testing matters most. If the well was flooded, start with whether well water is safe after flooding. Otherwise, how to test well water walks through what to test for and when.
Private Wells: Milky Water, Sputtering Faucets and Gas
Well owners have one cause city households almost never see: gas dissolved in the groundwater itself. The Minnesota Department of Health lists the signs. A sputtering or spitting faucet, or a gurgling noise from the well, may indicate methane or other dissolved gases, and the water may look clear with bubbles, milky, frothy, or have a bluish tint. The same page is careful to say those signs may come from other gases or from air getting into the system, so they're a reason to look closer, not proof.
The drinking question and the safety question are different here. Minnesota's health department says studies haven't linked drinking water that contains methane to short-term or long-term health effects, though very little research has been done. The real risk is in the air. Methane at 5 to 14 percent in air can ignite and explode, and it can build to that level in a poorly ventilated space like a well house or a basement, where a spark from a switch or a water heater flame can set it off. For that reason the department says methane should be vented outside any building or enclosed space.
Two more things from the same source. Methane in a well is usually natural, but it can come from sewage or waste, so wells producing it should be tested for coliform bacteria and nitrate. And some labs can test for methane itself, using a special sampling procedure. If your well water fizzes and the faucet spits, that's a call to a licensed well contractor and a lab, not a filter shopping trip.
Cloudy Only From a Filter, Softener or RO Faucet
Run the glass test on a regular tap that bypasses your treatment, such as a bathroom sink or an outdoor spigot if that's how your house is plumbed. If that water is clear and only the treated water is cloudy, the cause is the system, not your supply. The most common reason is air trapped after a cartridge change, which works its way out on its own. If it's your reverse osmosis faucet, why reverse osmosis water turns cloudy covers the causes specific to RO, and the water filter troubleshooting guide covers everything else.
Is Cloudy Tap Water Safe to Drink?
It depends on which result you got, and on whether you're on city water or a well. Air on a city supply is safe to drink, and hardness is a nuisance, not an emergency. The two results that call for action before anyone drinks the water are the ones that don't look like air:
- The glass stays cloudy or leaves sediment. Use another source for drinking and cooking until you know why. On city water, that answer comes from your utility. On a well, it comes from a lab test, and bacteria belong on the list.
- Well water fizzes and the faucet sputters. Here the drinking question comes second. Make sure the well house and basement are ventilated and nothing is sparking or burning nearby, then call a licensed well contractor and test for gas, coliform bacteria and nitrate.
Cloudy water that doesn't clear deserves a real answer.
If your glass stayed cloudy or left grit behind, a lab test tells you what's actually in the water before you spend anything on treatment. Crystal Quest® offers tests for both private wells and city water.
Frequently Asked Questions About Cloudy Tap Water
Why is only one faucet cloudy?
Then the cause is local to that faucet, not your water supply. Fill a glass from a second tap to confirm. A filter or reverse osmosis faucet, recent plumbing work on that line, or a single-handle faucet sitting partly on hot are the usual reasons. If every tap is cloudy, the cause is the water coming into the house.
Why did my water turn cloudy right after the city worked on the street?
Repairs and shutoffs can let air into the mains, and they can also stir up sediment. The glass test tells you which. Air clears in a few minutes. Sediment doesn't, and that's worth a call to your utility.
Can I boil cloudy water to fix it?
Boiling drives off air, so milky water from air will come out of the kettle clear. Boiling hard water can make it look worse, because heat pushes the minerals out as white scale. And boiling doesn't remove sediment. Follow your utility's advice if they've issued one.
Does a water filter fix cloudy water?
Not if it's air, because there's nothing to remove. For particles, a sediment filter is the usual fix, but only after you know the cause. On a well, a lab test should come first, because cloudiness after rain can mean bacteria that a sediment filter won't handle.
