Why Does My Water Smell Like Rotten Eggs, Sewage or Fishy?

Turning the tap on only to be greeted by the unpleasant smell of rotten eggs, sewage, or fish can be unsettling.

Strange smells in your water are usually caused by certain bacteria or contaminants. But, don’t worry – most of these issues can be fixed.

In this article, we’ll discuss:

• Why your water might smell like rotten eggs or sewage
• How to get rid of that rotten eggs smell
• Why your water could smell like chemicals or bleach
• What causes a gasoline-like smell in your water
• Why your water might have a fishy or moldy odor

Let’s dive in and help you understand what might be causing these smells and what you can do about them.

Why Does My Water Smell Like Rotten Eggs or Sewage?

Tap water can smell like rotten eggs, sewage, or fish because of the presence of hydrogen sulfide gas (H₂S) in it. This gas can be formed by sulfur bacteria in the drains, inside your water heater, or at the main water source.

1. Hydrogen Sulfide Gas in the Drains

If your sink or faucet gives off a sewage smell, it’s likely due to hydrogen sulfide gas (H₂S), often known as sulfur bacteria formation (thiobacillus). This gas isn’t in the water source but forms in the drains. When hair, dirt, food particles, and soap build up and clog your pipes, they decay and produce this gas, creating that unpleasant smell.

Here’s the easiest way to accurately determine if sulfur bacteria (hydrogen sulfide gas) is present in your home and not the water source: Fill a glass with water from the smelly faucet and take it to another room. Swirl it for a couple of minutes and then smell it again. If the odor is gone, it confirms the presence of hydrogen sulfide gas in the drain.

It’s good to know that bacteria and hydrogen sulfide gas in the faucets or drains won’t contaminate your water, so it’s not a health risk. However, having a stinky sink can be really annoying. Below, we’ll discuss ways to get rid of it.

2. Sulfur Bacteria Formation Inside the Water Heater

The smell of rotten eggs can also be caused by the accumulation of sulfur bacteria in your hot water heater.

This might happen if you haven’t used hot water for a while or if the water heater’s thermostat has been set too low. These conditions can create the perfect environment for bacteria to thrive and produce a potent sewage-like stench.

Additionally, most water heaters have a sacrificial anode rod made of magnesium or aluminum installed inside their water tanks. This metal rod protects the tank by attracting mineral buildup and corrosion, hence why it’s “sacrificial.”

However, when magnesium and aluminum react with sulfur in the water, they produce hydrogen sulfide gas. So, if your water heater’s anode rod corrodes, you might start noticing a sulfur smell coming off of your hot water.

To confirm the presence of bacteria in your water heater as the source of the rotten eggs smell, fill two glasses of water: one from a hot water faucet and one from a cold water one. Take both glasses into another room, swirl them for a couple of minutes, and smell them again.

If only the hot water smells like sulfur, then the problem lies within your water heater. On the other hand, if both glasses smell, the issue is likely with your water source.

You can check if the sacrificial anode rod is the culprit by opening up the water tank and inspecting the rod. If it’s corroded, that’s what’s causing the smell. If it’s not, bacterial activity is likely to blame.

3. Sulfur Bacteria Contamination at the Water Source

If both your hot and cold water smell like rotten eggs, the issue might be with your water source. There are two main sources of water: municipal water supply (also referred to as tap/city water) and private wells.

City water is regularly treated with chlorine and chloramines by water authorities, making sulfur bacteria contamination unlikely. However, private wells don’t receive the same treatment, so they can become breeding grounds for sulfur bacteria, especially in areas where groundwater is rich in sulfur.

Hydrogen sulfide can also enter the water source through surface water runoff or decaying organic matter in the soil and rocks where groundwater is found.

So, if both cold and hot water from your faucets smell like rotten eggs, you should immediately collect and send a water sample for testing. While hydrogen sulfide in drinking water is usually considered safe, it’s important not to ignore it. Other contaminants might be present as well, and it’s best to ensure your water is safe to drink.

How to Remove Rotten Eggs Smell in Water

If your water smells like rotten eggs, here are some steps you can take to fix it based on the source of the smell:

• If the source of the smell is sulfur bacteria accumulation in the drain, you need to disinfect the drain with chlorine. First, run cold water for 10-20 seconds. Then, turn it off and pour 2-3 cups of regular bleach down the drain. Wait 10-15 minutes, then flush the drain with hot water. Be careful not to get bleach in your eyes or on your skin.
• If the smell is the result of a corroded anode rod in your water heater, you need to remove or replace it. Keep in mind that removing the anode rod can reduce the lifespan of your water heater tank because, without it, the tank can corrode much faster. If you replace it, make sure to regularly inspect it to prevent the sulfur smell from returning.
• If there is sulfur bacteria accumulation in your water heater, you need to disinfect it and thoroughly flush the water. To disinfect the heater, turn off the water, power, and gas supply. After that, pour a gallon of bleach into it through its hot water outlet and reconnect the hot water line. Then, run all of the hot water faucets in your house until you smell bleach. As soon as you smell it, turn off the faucets and let the bleach stay inside the system for at least a day. As a last step, run all the hot water faucets again and leave them on until you can no longer smell bleach.
• If there is a sulfur bacteria accumulation in your water well, you need to thoroughly disinfect the well using shock chlorination. This involves adding a high concentration of chlorine to the water to disinfect the well and eliminate bacteria and other contaminants. Also, consider purchasing a sulfur water filter for well water to filter the water after the shock chlorination process.
• If the water well is contaminated with hydrogen sulfide, you should contact a professional well contractor to assess and repair any damage in your well casing. If they find no damage there, the hydrogen sulfide is probably coming from the groundwater. In this case, a whole-house filtration system with a reverse osmosis membrane and an ultraviolet filter can help.

Earlier on, we mentioned that city water isn’t likely to be contaminated by hydrogen sulfide since it’s regularly treated with chlorine and chloramines. This doesn’t mean that the water can’t get contaminated though. So, it’s still a good idea to contact your water supplier if you test your water and discover the presence of hydrogen sulfide gas (H₂S).

Chemical, Medicinal, or Bleach-Like Smell in Water

Over-chlorination (excess amount of chlorine in water) can give water a chemical, medicinal, or bleach-like odor reminiscent of swimming pools. When chlorine molecules interact with organic properties like bacteria, fungi, or algae, they can produce a distinct chemical or medicinal smell.

Tap water suppliers add chlorine to the water to eliminate bacteria, viruses, and other harmful particles. 2 parts per million (ppm) is the recommended amount of chlorine for water treatment, but sometimes, the chlorine concentration can reach 5 ppm in cases where the water is excessively contaminated and needs to be treated more severely than usual. Whenever there’s an excessive amount of chlorine in the water, it’ll inevitably emit a strong bleach-like odor in your home.

In addition, private wells can be treated with shock chlorination every once in a while to remove or prevent contamination. This water treatment method could also be the reason for the bleach smell.

How to Remove the Bleach-Like Smell From Your Water

If your water has a bleach-like smell, here are several methods you can use to eliminate it:

• Run your water for a while: After shock chlorination has been used to disinfect a well or an entire water system, any lingering bleach smell can be removed by letting water flow from the faucets for a couple of minutes since chlorine evaporates when subjected to air.
• Flush your well: Flushing a well is a complex process that requires the services of a professional contractor.
• Use an activated carbon filter. This filter effectively removes chlorine and other chemicals from your water. You can install one on your faucet or use a filtered water pitcher.
• Install a water softener: If you have hard water, a water softener can help reduce the amount of chlorine needed, decreasing the bleach-like smell.
• Use a reverse osmosis system: This system filters out chlorine and other contaminants, providing clean, odor-free water. It’s a highly effective method for removing bleach-like smells from your water.

Reach out to your supplier: If the smell persists, contact your water supplier. They can test the water to ensure chlorine levels are safe and advise you on further steps.

Water Smells Like Gasoline

If your water smells like gasoline or fuel, it’s a serious issue that shouldn’t be ignored. This smell often indicates the presence of volatile organic compounds (VOCs) in your water supply.

Gasoline smell can also appear because of the following reasons:

• A fuel leak near your water source, especially if you rely on a well, can contaminate your water with VOCs.
• Contaminants from landfills or industrial facilities can seep into the water supply, causing it to smell like gasoline.
• Pesticides and other chemicals used in agriculture can enter the water supply and produce a fuel-like odor.

That said, the gasoline smell in your water can’t be resolved independently. If you notice a gasoline smell, you should immediately stop drinking or using the water. Contaminated water can be hazardous to your health.

If you have a private well, get in touch with a professional water well service contractor. They can assess the situation and suggest the best course of action.

Finally, if your water comes from a municipal source, inform your water supplier right away so they can investigate and address the issue.

Fishy or Musty/Moldy Smell in Water

Water smelling like fish or mold often indicates the presence of chlorine, barium, or radium in the water. Decaying organic matter in the drains is also another possible source of fish odor.

Similar to chlorine, chloramines are also utilized by water suppliers and municipalities to decontaminate city water from pathogens like bacteria and microbes. Barium and radium, on the other hand, are naturally found elements and can seep into underground water sources through surface water runoffs after heavy rains.

One way to verify the source of the fishy smell is to fill a glass of water, take it to another room, and swirl it for a couple of minutes. If the smell disappears, the issue is likely in your drains. If the smell remains, it’s in the water.

To address the issue, chlorinate and flush your drains to remove any organic material that might be causing the odor. If chemicals like chloramines, barium, or radium are causing the smell, consider installing a water filtration system. This can help remove these contaminants and improve the taste and smell of your water.

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