Why is my tap water cloudy white? The glass test

Short answer

Cloudy or milky tap water is almost always dissolved air, and a glass of water decides it in about 1 minute. Fill a clear glass, set it down and watch: LA County Public Works says dissolved air escapes on its own and clarity is typically restored within a minute, clearing from the bottom of the glass upward as the bubbles rise. Water that stays cloudy, settles, or streaks is turbidity, suspended sediment measured in NTU, which EPA’s Surface Water Treatment Rule limits for public surface-water systems. A hazy glass with a metallic taste in a house with galvanized pipe points to zinc, where EPA’s secondary standard is 5 mg/L. A milky, frothy or bubbling glass from a private well with a gas smell is a methane question: Penn State Extension calls for immediate action above 28 mg/L, and the test is a lab sample, not a glass.

If your glass cleared from the bottom up while you read that, you can leave now: dissolved air is not a contaminant, and nothing on this page or in any shop fixes it.

What does the glass tell you?

The glass test is the whole diagnosis for most readers. Run cold water for a few seconds, fill a clean clear glass, set it on the counter and watch it for a minute.

What the glass does	Likely cause	Confirm with
Milky white, clears from the bottom up within about 1 minute, no smell	Dissolved air	The clearing itself, per LA County Public Works; repeat on hot and cold taps
Milky to gray, does not clear, settles to the bottom or streaks	Turbidity (suspended sediment)	A settling test and a lab turbidity reading in NTU; the sediment and turbidity guide carries the NTU limits and filter classes
Hazy with a metallic or bitter taste, worse on hot water or after plumbing work	Zinc from galvanized steel pipe corrosion	A metals test against EPA’s 5 mg/L secondary standard for zinc
Milky, frothy or bubbling, gas smell, private well, near gas drilling or a new well	Methane	A lab sample; never a flame check indoors, per the Minnesota Department of Health
Cloudy only since a new or rebedded water softener, fading over several regenerations	Resin fines from the softener	The install date; no source this session publishes how long fines take to clear

Dissolved air is gas that cold, pressurized water holds in solution until the pressure drops at the tap. Turbidity is the cloudiness caused by particles suspended in the water. Those two look alike for the first ten seconds and nothing alike after a minute.

What do the numbers mean?

USGS explains that turbidity is measured by shining a light through the water and is reported in nephelometric turbidity units (NTU). It is a scattering measurement, not a particle count, so a lab reading is the only number worth acting on.

EPA’s Surface Water Treatment Rule holds public surface-water systems to 0.3 NTU in 95 percent of monthly samples and never above 1 NTU. That limit binds your utility, not your well; a private well has no federal turbidity limit, and the sediment guide linked above covers the micron sizing that replaces it.

EPA’s secondary standard for zinc is 5 mg/L, and the effect EPA lists beside it is a metallic taste. Secondary standards are aesthetic guidance that EPA does not enforce, which is why the taste, not a regulator, is usually what sends an owner of a galvanized house to a metals test.

Methane carries the only numbers on this page that are not about appearance. The Minnesota Department of Health says methane in air between 5 and 14 percent by volume can ignite and explode; Penn State Extension prints the range as 5 to 15 percent. This page keeps both figures as published rather than reconciling them.

Penn State Extension says wells with methane below 10 mg/L are generally considered safe for use, and that owners of wells above 28 mg/L should take immediate action to reduce the concentration. The Minnesota Department of Health says methane from the well and water system should be vented to the atmosphere, outside enclosed spaces such as well houses or homes.

Which treatment class fits?

Glass result	Treatment class	Why
Clears bottom-up in about 1 minute	None	Dissolved air is not a contaminant; no limit exists and no filter changes it
Stays cloudy or settles	Sediment filtration sized by micron	Turbidity is particles; the sediment guide’s NTU limits set the public-system reference and pick the cartridge class
Metallic taste, galvanized pipe	Pipe replacement or a point-of-use filter chosen after a metals test	Zinc’s 5 mg/L secondary standard is aesthetic; the test decides whether the number is even near it
Frothy, gas smell, private well	Venting and aeration by a well professional	Methane is an explosion question first; Penn State Extension’s 28 mg/L action level and the Minnesota Department of Health venting rule set the path
New softener, fading haze	Wait through several regenerations, then flush	Resin fines are a startup nuisance with no regulatory limit and no published clearing figure

No product is recommended on this page because three of the five rows need no product and the other two need a test result before any cartridge is chosen. Methane in particular is not a filter purchase: both the Minnesota Department of Health and Penn State Extension describe it as a venting and lab-test issue.

Before you buy anything

Do not order a sediment filter for cloudy water until a glass has sat on the counter for a full minute. Most readers will watch it clear and owe nobody anything. If it stays cloudy, the next purchase is a lab turbidity reading in NTU and, on a well, a settling test, because the micron rating that fits depends on what is actually suspended. If the glass is frothy and the well house smells of gas, do not buy anything at all: call a well professional and have a methane sample drawn for a lab, because Penn State Extension’s 28 mg/L action level is a number only a lab can give you.

Why does the resin-fines case get its own row?

A new or freshly rebedded softener sheds fine resin dust into the first tanks of service water, and the haze fades over the first few regenerations as the bed settles.

That mechanism is well known in the trade, but no primary source read this session publishes a figure for how many gallons or days it takes, so this page prints none.

The tell is timing. If the cloudiness began the day the softener went in and the glass test does not clear like air, note the install date and give the unit several regenerations before calling it turbidity. If the haze is still there a few weeks later, run the settling test from the sediment guide.

What should you do first?

Fill a clear glass from the cold tap, set it down and time it: clearing from the bottom up within about 1 minute is dissolved air, and you are done.
If it stays cloudy, run the settling test in the sediment and turbidity guide and order a lab turbidity reading in NTU.
If the house has galvanized steel pipe and the water tastes metallic, add zinc to the metals panel and compare the result with EPA’s 5 mg/L secondary standard.
If the glass is frothy or bubbling from a private well, especially with a gas smell, stop the glass test and have a methane sample drawn for a lab; handle anything above Penn State Extension’s 28 mg/L as an immediate venting job.
If a softener was installed or rebedded in the last few weeks, wait through several regenerations before buying any filter.

Frequently asked questions

Why does my tap water look milky but clear up in the glass?

That is dissolved air. Cold water under pressure holds more gas than it can once it leaves the tap, so it comes out as thousands of tiny bubbles that read as milk. LA County Public Works says clarity is typically restored within about a minute when you pour a glass and let it stand. It clears from the bottom up because the bubbles rise. Nothing needs fixing.

What is the EPA limit for zinc in drinking water, and can zinc make water look cloudy?

EPA's secondary drinking water standard for zinc is 5 mg/L, and the effect EPA lists beside it is a metallic taste. Secondary standards are aesthetic guidance, not enforceable limits. In a house with galvanized steel pipe, corrosion releases zinc and can leave water hazy with a metallic or bitter taste, especially on hot water or after plumbing work. A metals test confirms it; a glass test does not.

How is turbidity measured in water?

USGS explains that turbidity is measured by shining a light through the water and reading how much is scattered, reported in nephelometric turbidity units, or NTU. A lab or a portable turbidimeter gives the number. EPA's Surface Water Treatment Rule holds public surface-water systems to 0.3 NTU in 95 percent of monthly samples and never above 1 NTU; a private well has no federal turbidity limit.

What does methane in well water look like, and why is it handled differently?

The Minnesota Department of Health says water carrying methane may look clear with bubbles, milky, frothy, or have a bluish tint, so it mimics dissolved air in a glass. The difference is that methane in air between 5 and 14 percent by volume can ignite and explode, so the department says it must be vented outdoors, never inside a well house or home. Test it; do not filter it.

What methane level in a well is considered safe, and when should I act?

Penn State Extension says wells with methane below 10 mg/L are generally considered safe for use, and that owners of wells above 28 mg/L should take immediate action to reduce the concentration. Penn State publishes no separate guidance for readings between those two figures on the page read for this article. The number comes from a lab sample, not from the glass test, which cannot tell methane from air.

Fact sheet and how to cite this page

Answer: Milky tap water that clears from the bottom of a glass upward within about 1 minute is dissolved air, per LA County Public Works, and needs no filter. Water that stays cloudy is turbidity, which EPA’s Surface Water Treatment Rule caps at 1 NTU for public surface-water systems. A milky, frothy well glass with a gas smell is a methane test, and Penn State Extension sets its action level at 28 mg/L.
Basis: EPA Surface Water Treatment Rule turbidity provisions (0.3 NTU in 95 percent of monthly samples, never above 1 NTU, public surface-water systems only); EPA secondary standard for zinc, 5 mg/L; Penn State Extension methane figures of 10 mg/L and 28 mg/L.
Assumptions: The glass test is done with cold water in a clean clear glass, watched for a minute
The EPA turbidity limits apply to public surface-water systems; no federal limit exists for a private well
Resin fines from a new softener are described by mechanism only; no source this session publishes a figure for how long they take to clear
Method: Limits and mechanisms read on 2026-09-15 from LA County Public Works, EPA’s secondary standards page and SWTR turbidity guidance, USGS, Minnesota Department of Health and Penn State Extension; nothing was tested.
Primary source: EPA, Guidance Manual for Compliance with the Surface Water Treatment Rules: Turbidity Provisions (government or regulatory source)
Facts verified: 15 September 2026
Last updated: 15 September 2026
Canonical URL: https://ownerspec.com/water/guides/cloudy-milky-tap-water/
Cite as: OwnerSpec, "Cloudy or milky tap water: the glass test that separates dissolved air from turbidity, zinc and methane", https://ownerspec.com/water/guides/cloudy-milky-tap-water/, facts verified 15 September 2026.

Every figure above also appears, with its source, in the article. All sources · How OwnerSpec verifies numbers

Sources

LA County Public Works, Cloudy Water (government or regulatory source)
EPA, Secondary Drinking Water Standards: Guidance for Nuisance Chemicals (government or regulatory source)
EPA, Guidance Manual for Compliance with the Surface Water Treatment Rules: Turbidity Provisions (government or regulatory source)
USGS Water Science School, Turbidity and Water (government or regulatory source)
Minnesota Department of Health, Methane in Well Water (government or regulatory source)
Penn State Extension, Methane Gas and Its Removal from Water Wells (university or extension service)