why does my sink water smell like sewer

David Kissel, Uttam Saha, Leticia Sonon, Jake Mowrer, and Uttam Saha
Agricultural and Environmental Services Laboratories at the University of Georgia

• Locating the Source of the Odor
• Common odor issues in drinking water, possible causes, and proposed solutions
• References

Homeowners may sometimes notice foul scents in their home water. In many circumstances, water testing cannot pinpoint the particular origin of the odor; nonetheless, this paper includes a few broad advice for correcting some frequent causes of home water smells.

Locating the Source of the Odor

If the odor is present in all water faucets, the issue is most likely in the main water supply. If it only happens with particular faucets, the issue is most likely with the fittings or pipes that feed that specific faucets. If the issue goes away after a few minutes of running the water, the fault is somewhere in the domestic plumbing system. If the odor persists, the cause of the issue might be the water supply or a combination of the water supply and the plumbing system. Figure 1 outlines the possible sources of odors in water.

Figure 1. A decision tree to aid in the identification of causes of home water odor.

Corrective procedures are recommended for smells emanating from the plumbing system or the well system. Contact your water provider if you get your water from a public water supply (PWS) and the odor is thought to be coming from the water source line. This is particularly true if your neighbors are also experiencing odor issues.

Drinking Water: Common odor problems, probable causes and suggested corrective measures

If an odor issue in your home water and its cause are not listed here, speak with a drinking water expert from your water provider (if you use public water), county health agency, or UGA Cooperative Extension agent (1-800-ASK-UGA-1).

a. Bleach, Chemical or Medicinal Odor

To avoid bacterial development, public water providers often chlorinate the water. The typical amount of free chlorine in PWS drinking water is 0.2 – 2.0 parts per million (ppm), although values may reach 5.0 ppm. Odors caused by chlorine addition normally disappear within few minutes of exposure to air.

The addition of chlorine to water by shock chlorination of a well or plumbing system results in a distinct bleach (chlorine) odor. When the chlorine has entirely dissipated, the bleach smell will disappear. Turning on outdoor faucets and letting the water flow until the odor is gone is required.

In rare situations, the additional chlorine may interact with organic compounds in the plumbing system, causing the water to smell. After a few minutes of running the water, the stink should be gone. Figure 1 shows how to find the source of the odor. If you get your water from a well and the issue seems to be in your plumbing or well system, your complete water system should be cleansed, ideally by a qualified well driller or pump installer. Contact your water supply authority if you are on a PWS and the issue seems to be with the water supply line.

b. Rotten Eggs (Sulfurous), Decayed or Sewage-like Odor

A rotten egg (or sulfurous), rotted, or sewage-like stench in home water is often caused by bacterial activity, which may be caused by:

• Bacteria developing in the drain: The most prevalent source of unpleasant scents. Organic stuff, such as hair, soap, and food waste, may collect on the drain’s walls over time. These deposits provide food for bacteria to thrive on. Bacteria have the ability to create a gas that smells like rotten eggs or sewage. Take the following two actions to address this issue:

1. First, be sure that the scent is present in both cold and hot water, and that it is coming from one or more faucets, but not all. Fill a glass with the smelly water from the sink, then move away from the sink and swirl the water around within the glass a few times. If the issue is in the drain, the tap water in the glass should be odorless.
2. If the water in the glass does not smell, disinfect the drain and flush it.

• Bacteria in the water heater: Bacteria in the water heater may generate a rotten egg or sewage odor. This is common when hot water is left unused, the water heater is switched off for an extended period of time, or the heater’s thermostat is set too low. The germs that cause this condition are not generally harmful to one’s health; nonetheless, the taste and odor may be highly unpleasant. The following measures are proposed to resolve this issue:

1. Check that hot water stinks but cold water does not. The stench is often caused by a magnesium heating rod in the hot water tank.
2. A qualified plumber may replace the heater’s magnesium rod with a suitable substitute, such as an aluminum rod.

• Bacteria in the well: If issues with the drain or water heater have been checked out, the stench might be coming from the water source. The water should not be used since it may contain hazardous microorganisms. The following measures are proposed to resolve this issue:

1. If you are on your own well, the natural groundwater chemistry may be supporting bacterial growth in the well. Shock chlorinate the well and pump out water until the chlorine odor disappears. For a step-by-step shock chlorination procedure, refer to the University of Georgia publication “Disinfecting Your Well Water: Shock Chlorination.”
2. A faulty or incorrectly situated septic system might be near your well. Contact the health department in your county.
3. If you are on a PWS, immediately notify your water supply authority or county health department.

For more information about rotten egg odor, refer to the University of Georgia publication “Your Household Water Quality: Hydrogen Sulfide and Sulfate.”

c. Musty, Moldy, Earthy, Grassy or Fishy Odor

Although these scents are innocuous, human taste and smell are extraordinarily sensitive even at low levels. These scents might be caused by:

• Decaying organic matter in the drain
• Pollution of well water from surface drainage

Bacteria are quite frequent in both instances. The rotting organic debris accumulated in the drain over time is by far the most typical source of this sort of issue. Fill a glass with tap water, then move away from the sink and swirl the water around within the glass a few times to ensure the issue is not in the well. If the issue is in the drain, the tap water in the glass should be odorless. The stink should be eliminated by disinfecting, cleaning, and flushing the drain.

The odor might possibly be coming from the reservoir/pressure tank. Cleaning and maintaining the reservoir/pressure tank on a regular basis may prevent germs from developing to the point where they generate odor in the water. Less often, some forms of algae, fungus, and bacteria growing in the water supply, particularly during warm weather, might change the odor of the water.

If the issue is in the well, shock chlorinate it and pump out a lot of water until the chlorine smell goes away. If the issue continues, think about installing:

1. An activated carbon filter OR
2. An activated carbon filter is used after an automated chlorinator.

If you have a PWS and not enough chlorine is used to disinfect the water, some bacteria may develop in the supply line and generate unpleasant smells. Contact your county’s health department or the water supply authority.

d. Petroleum, Gasoline, Turpentine, Fuel-like or Solvent-like Odor

Even though these odor issues are uncommon, they may be dangerous. These scents might be caused by:

• A gasoline tank that is leaking or an underground fuel storage tank near your well
• Factory or landfill discharge compromising the water supply
• Agricultural run-off damaging the water supply

Stop drinking the water since it may have a number of negative health effects, including but not limited to:

1. Anemia
2. Increased risk of cancer
3. Liver and kidney problems

Remedial actions include:

1. Inform your county’s health agency about the situation.
2. Eliminate the source of the problem
3. After verifying the kind and source of the chemical pollutant, install an activated carbon filter system.

If you are on a PWS, immediately notify your water supply authority and county health department.

e. Other Odors

Odor	Probable Cause	Possible Health Effects	Suggested Remedies
Detergent odor or foaming water	Septic tank leakage into water supply.	Illnesses of the gastrointestinal tract (diarrhea, vomiting, cramps).	Eliminate source and shock chlorinate well
Methane gas odor	Organic chemicals discovered naturally degrading in shallow wells near marshes. Houses built above/near old landfills or aquifers overlying oil fields.	Gas is explosive and toxic to breathe.	A well vent can remove methane from some wells. Check with a professional well contractor in your region to discover whether a well vent may be installed. installed on your well. Aeration can also be used to remove methane. Repump and install a domestic deaeration system.
Sharp chemical odor	Pesticide or other pollutant leaching into groundwater.	Anemia or other blood disorders. Nervous system or reproductive disorders. Increased chance of cancer or stomach, liver, and renal disorders, among other things.	Activated carbon filter OR Reverse osmosis.

References

Color, Taste, and Odor Problems in Drinking Water. Fact Sheet. Washington Department of Health, January, 2011. http://www.doh.wa.gov/portals/1/Documents/pubs/331-286.pdf

Color, Taste, and Odor: What you should know. Massachusetts Department of Environmental Protection. http://www.mass.gov/dep/water/drinking/color.htm

Liukkonen, B. 2011. Why Well Water Smells Bad. University of Minnesota Extension. http://www.extension.umn.edu/environment/housing-technology/moisture-management/why-water-smells-bad/.

Saha, U., L. Sonon, M. Risse and D. Kissel. 2011. Water Quality and Common Treatments for Private Drinking Water Systems. Bulletin 939 (Revised July 2011). University of Georgia Cooperative Extension. https://extension.uga.edu/publications/detail.html?number=B939

World Health Organization. 2008. Drinking Water Quality Guidelines. Chapter ten. Taste, odor, and appearance are all aspects of acceptability. World Health Organization Press, Geneva, Switzerland.

Reviewers: University of Georgia’s Mark Risse and William Carlan; Texas A&M University’s Kristine Uhlman; and Beth Thomas of AdEdge Water Technologies, Inc.

Status and Revision History
Published on May 15, 2012
Published with Full Review on Mar 28, 2017
Published with Full Review on Sep 13, 2021