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Stinky Water: Your Odor Guide

Stinky Water: Your Odor Guide


Whether it stinks like rotten eggs or bleach, smelly water might have you worried.

The exact cause of water odors can be challenging to determine. Therefore, we have created a handy guide to help you identify and treat common causes of household water smells, as well as what to do about it.

How to locate the source of smelly water:

The first step to solving a smelly water problem is determining where the smell is coming from. Here’s a chart that can help you locate potential sources:

Water Odor Chart

Common Water Odors and Ways to Fix Them:

Water Smells like Bleach, Chlorine, or Medicine

Chlorine is used by most public water suppliers to prevent bacterial growth. When added to a well (via shock chlorination) or plumbing system, chlorine produces a strong bleach odor.

The best way to eliminate the chlorine smell is turn on your faucets (preferably outdoors) and let the water run until the smell is gone. In some cases, chlorine interacts with organic materials that have accumulated in your plumbing system, which increase the musty-bleach smell.

Volatile Compounds Water TestConcerned about the effects of chlorine? Learn more here and take a look at our test specifically targeting chlorine disinfection byproducts. If your water comes from a public water supply, you should contact your water supply authority.

If you get your water from a well and are smelling a chlorine or bleach odor, you may need to have your water system flushed.

Water Smells like Rotten Eggs

Generally, a sewage-like or rotten egg odor in your tap water results when sulfur-reducing bacteria grow in your drain, water heater, or well. These bacteria, which use sulfur as an energy source, chemically change natural sulfates in water into hydrogen sulfide-which emits a distinct rotten egg odor.

Hydrogen Sulfide bacteria water testIf your water smells like rotten eggs, we can help! We have a specifically targeted, at home, self-testing kit for hydrogen sulfide bacteria.

Bacterial growth in the drain:

This is the most common cause for these types of odors. When organic matter (hair, soap, food waste etc.) accumulate in the drain, bacteria can thrive and produce gas that smells like rotten eggs.

How to address and remove bacteria in the drain:

  1. Making sure bacteria growth in the drain is the issue:
    Both the cold and hot water smell (at a single tap), and that the smell is not coming out of all faucets. Then, fill a glass with water from the faucet that does smell and step away from the sink so you can't smell any residual odor from the tap. Swirl water inside the glass a few times. Wait 30 seconds–and if the glass no longer smells, then this test suggests you likely have bacteria in the drain causing the smell.

  2. If the water in the glass does not have an odor, the best plan of action is to disinfect and flush the drain.


Bacterial growth in your water heater:

When hot water goes unused, bacteria in your water heater can produce a rotten egg or sewage-like smell. This occurs if your water heater is turned off for a significant amount of time or if the thermostat on the heater is set too low. These bacteria are generally not a health threat.

How to address and remove bacteria in your water heater:

Making sure bacteria growth in the water heater is the issue:

  1. Your hot water smells, but your cold water does not.This generally means that the smell originates from the magnesium heating rod in your hot water tank.
  2. If only your hot water smells...Call a plumber to replace your magnesium heating rod with an alternative, like an aluminum rod.


Bacterial growth at the water source:

If none of the above steps lead to an answer, the odor may be from your water source itself. If this is the case, do not use or drink the water until you test your water–as it may contain harmful bacteria.

Microbiology Water TestIf this is the case, take a look at the Tap Score Total Microbiology Screen Water Test. This all-inclusive pathogen and microbiological screening provides identification and enumeration of thousands of species of bacteria, protozoa, algae and more in tap water, well water, and other surface water.

Recommendation if your source is a private well:

  1. Treating your well with shock chlorination (take a look at this step-by-step guide to disinfecting your well) because the natural chemistry of your groundwater may be supporting bacterial growth.
  2. Contacting your local health department in case a defective or improperly located septic system is located near your property.

    Recommendation if your source is a public utility:

    1. Contacting your water supply authority or county health department.
    2. Try to identify if your water source has been switched or if algal blooms have affected your water system’s water supply.


      Water Smells Musty, Moldy, Earthy, Grassy or Fishy

      When your water smells this way it is very likely that bacteria is present. Reasons your water may smell moldy include:

      Decaying matter in your drain:

      This is the most common cause for moldy smelling water. The best way to combat decaying matter in your drain is to disinfect, clean, and flush your drain.

       Private well? Well water pollution from surface drainage: Moldy water can be attributed to certain types of algae, fungi, or bacteria growing in your water supply–particularly during warm weather. We recommend treating your well with shock chlorination. If the problem persists, you may want to install an activated carbon filter or an automatic chlorinator (followed by an activated carbon filter).

       Public water? Insufficient chlorine: If you are on a public water supply, certain types of bacteria may grow in your supply line if an insufficient amount of chlorine is added. If you suspect this is the case, contact your water supply authority.

      How do you know how much chlorine in your water? Testing directly at the tap is the most accurate way. While we usually suggest testing your water a certified laboratory, chlorine is best tested at some due to its volatile nature. Take a look at our DIY chlorine test strips–they are included in every Tap Score City Water Testing package. They are also available as an add-on for any test here.

      Water Smells like Gasoline or Petroleum

      These odors are rare, but could be very serious. If you are on a public water supply, contact both your water supplier and county health department immediately. Fuel-like odors may be due to:

      1. A leaking underground fuel storage tank near your well
      2. Contamination due to discharge from factories landfills
      3. Runoff from agriculture leaching into your water supply

      If any of these are the case, stop drinking the water, as it may have adverse health effects, including:

      • Anemia
      • Increased risk of cancer
      • Liver and kidney problems

      Do you need help with smelly water?

      Drinking water odors may come from a variety of reasons–some harmless, while others are potentially serious. If you aren’t sure the cause of stinky water or not sure how to treat it–send us a message at

      Talk to an expert

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