Why Does My Tap Water Smell or Taste Strange? A Smell-by-Smell Guide

Most strange smells and tastes in tap water are harmless. A swimming-pool smell usually means the disinfectant your utility adds on purpose. A rotten egg smell that only shows up in hot water usually comes from your water heater. An earthy or musty taste usually comes from natural compounds made by algae and bacteria in lakes and rivers. The smells that deserve a phone call are the unusual ones: gasoline, solvents, sewage, or any sudden change you can’t explain.

First, a quick test: is it the water or the drain?

Before blaming the water, rule out the sink. Odors from a drain or garbage disposal can drift up while the faucet runs and seem like they come from the water.

Washington State’s Department of Health suggests a simple check: put a little water in a narrow glass, step away from the sink, swirl it, and smell it. If the water in the glass has no odor, the drain is the likely culprit. Then try a few more things:

Hot vs. cold. Smell the cold water and the hot water separately. A smell only in the hot water points to your water heater.
One tap vs. every tap. A smell at one faucet points to that fixture or the pipes nearby. A smell at every faucet points to the water supply or your main plumbing.
First draw vs. after running. Washington’s guidance is that a problem that goes away after running the water for a few minutes is somewhere in your household plumbing.

Many of these fall under “aesthetic” standards

The EPA sets two kinds of drinking water standards. Primary standards are enforceable limits based on health. Secondary standards cover things like taste, odor, color and staining. The EPA says secondary contaminants are not considered a risk to human health at the secondary level, and those guidelines are not federally enforceable (fluoride is the one partial exception).

Many taste and odor problems, such as iron, manganese, chloride, sulfate and general odor, fall under the secondary standards. Unpleasant does not automatically mean unsafe, but a few smells do point to a real problem.

Chlorine or “swimming pool” smell

What it usually is: The disinfectant your utility adds to kill germs. Utilities use either chlorine or chloramine (chlorine combined with ammonia) and keep a small amount in the water all the way to your tap so germs can’t regrow in the pipes.

Is it safe? The CDC says chlorine or chloramine at levels up to 4 milligrams per liter (4 ppm) is considered safe in drinking water. The CDC also notes that chlorinated water can taste and smell different, especially at higher levels. New York City’s water department adds that the chlorine taste tends to be more noticeable in warmer weather.

What you can do:

Chill water in a covered pitcher in the fridge. NYC’s water department suggests this to reduce chlorine taste.
Letting water sit out removes chlorine over time, but the CDC notes it does not remove chloramine.
A carbon filter certified to NSF/ANSI 42 for chlorine reduction removes most of the taste. If your utility uses chloramine, check that the filter is certified for chloramine specifically.

Special cases: The CDC says chlorine and chloramine must be removed before water is used for kidney dialysis, and that fish, turtles and frogs should not be kept in chlorinated or chloraminated water. For a deeper look, see our guide to chlorine and chloramine in tap water.

When to call: If the chlorine smell suddenly becomes much stronger than usual, call your utility. It can tell you whether anything has changed in treatment or in your neighborhood’s pipes.

Rotten egg or sulfur smell

What it usually is: Hydrogen sulfide gas. It has two common sources: the water heater, and the groundwater itself (mostly a private well issue). Penn State Extension notes that most people can smell it at concentrations well below 0.5 mg/L, and that the nose detects it well before it causes health concerns.

If it’s only in the hot water: The Minnesota Department of Health explains that water heaters can make hydrogen sulfide in two ways. The warm tank can host sulfur bacteria, and sulfate in the water can react with the tank’s anode rod, a metal rod (often magnesium) that protects the tank from corrosion. Penn State Extension notes that a smell in the hot water only usually points to this reaction.

Fixes that state and extension sources describe:

Replace the anode rod with one made of a different metal. Penn State Extension says swapping the magnesium rod for an aluminum one should eliminate the odor while still protecting the tank. Don’t just pull the rod out: Minnesota’s health department warns that removing the anode may significantly shorten the heater’s life, and Penn State says removing it will likely void the manufacturer’s warranty.
Disinfect and flush the water heater with a chlorine bleach solution, following the manufacturer’s directions.
Heat treatment. Minnesota lists raising the tank to 160°F for several hours as an option, but warns that it can be dangerous. Check the pressure relief valve first and turn the thermostat back down afterward to prevent scalding. This is a good job for a plumber.

If it’s in the cold water too: On a public water system, call your utility. On a private well, Minnesota’s health department says the smell usually does not relate to the sanitary quality of the water, but because pollution is occasionally the cause, it recommends testing for coliform bacteria and nitrate. See our well water testing guide for how to do that.

Earthy, musty or “dirt” taste

What it usually is: Two natural compounds called geosmin and MIB (2-methylisoborneol). The U.S. Geological Survey says they are produced by cyanobacteria and by soil and water bacteria called actinomycetes, and that most actinomycetes give public water supplies an earthy or musty odor.

Is it safe? USGS describes these compounds as “nuisance” constituents and says they are not harmful. People can taste them at extremely low concentrations, which is why a utility can meet every health standard and still get complaints.

When it happens: These tastes tend to come and go, rising when algae and bacteria bloom in the lakes, reservoirs and rivers a utility draws from.

What you can do: An activated carbon filter certified for taste and odor reduction may help. A call to your utility will tell you whether it knows about the problem and is adjusting treatment.

Metallic taste

What it usually is: Metals from pipes or from the source water. In the EPA’s secondary standards table, a metallic taste is linked to copper, iron, manganese, zinc, low pH, and corrosive water.

Why it matters more than other tastes: A metallic taste is often harmless, but it can be a sign that water is corroding your plumbing. Corrosion is also how lead and copper get into tap water.

Copper has a health-based action level of 1.3 mg/L under EPA rules. The EPA lists short-term effects of too much copper as stomach upset, and long-term effects as liver or kidney damage. Blue-green stains on sinks and tubs are a common sign of copper.
Lead has no taste you can rely on. A metallic taste does not mean lead is present, and the absence of a taste does not mean it isn’t. If your home has older plumbing, read our guide to lead in tap water.

What you can do: Run cold water for a short time before drinking if it has sat in the pipes for hours, use only cold water for drinking and cooking, and consider a test. See how to test your tap water at home.

Salty or brackish taste

What it usually is: Dissolved minerals. The EPA’s secondary standards link a salty taste to chloride (250 mg/L), sulfate (250 mg/L) and total dissolved solids (500 mg/L). These are aesthetic guidelines, not health limits.

Washington’s health department adds sodium, magnesium and potassium to the list. A home water softener can also add sodium; the Illinois Department of Public Health notes this matters for people on low-sodium diets.

When to call: If the taste changes suddenly or you are on a sodium-restricted diet, ask your utility for its sodium and chloride levels. They often appear in the annual water quality report; see how to read your water quality report.

Smells that mean “stop and call”

Some odors are rare but potentially serious. State health agencies advise taking these seriously:

Gasoline, fuel, turpentine or solvent smell. Washington State’s Department of Health calls these odors rare but potentially serious, says not to use the water, and notes that a leaking underground storage tank may be the cause. Wisconsin’s health department likewise advises stopping drinking or cooking with water if you can smell gasoline or see an oily sheen.
A sulfur or other foul smell that isn’t the drain or water heater. Washington’s guidance is that if you rule out both and the odor is definitely coming from the tap water, don’t use it.
A salty taste in a coastal area. Washington notes that seawater seeping into a freshwater supply could be a health threat.
A sudden, unexplained change in taste or odor, especially with a change in color or cloudiness.

Who to call: on a public water system, call your water utility first. On a private well, call your local or state health department, as Washington State’s health department advises.

One more caution: many contaminants have no smell or taste at all. The American Academy of Pediatrics notes, for example, that lead can’t be detected by sight, taste or smell. A normal smell is not proof that water is safe, which is why testing and your utility’s reports matter. You can look up your utility’s EPA compliance record by searching your ZIP code.

Quick reference

Smell or taste	Most common cause	Usually harmful?	What to do
Chlorine / pool	Disinfectant	No (up to 4 mg/L per CDC)	Chill it, carbon filter (NSF 42)
Rotten egg, hot water only	Water heater anode reaction	No	Swap anode, disinfect tank (plumber)
Rotten egg, cold water too	Groundwater or bacteria	Usually not	Call utility; well owners test
Earthy / musty	Geosmin, MIB	No (USGS)	Carbon filter, tell your utility
Metallic	Copper, iron, corrosion	Sometimes	Flush, use cold water, test
Salty	Chloride, sulfate, softener	Usually not	Check report, ask utility
Gasoline / solvent	Fuel or chemical contamination	Possibly	Stop using, call utility or health dept.