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

Scott Winfield
Written by Scott Winfield
Last Updated on

What if when you twist the knob of your faucet, the water emits a peculiar or awful smell like bleach, rotten eggs, or sewage? The sewage or bleach-like smell in water is usually a sign of sulfur bacteria formation in the drains or a contaminated water source.

In this article, we’ll discuss:

Why Does My Water Smell Like Rotten Eggs or Sewage?

Water smells like rotten eggs, sewage or sulfur due to the presence of hydrogen sulfide gas (H₂S). This gas is caused by sulfur bacteria formation in the drains, inside the water heater, or at the main water source.

1. Hydrogen Sulfide Gas in the Drains Causes Sewage Smell

Sewage smell from the sink/faucet is a clear sign of hydrogen sulfide gas (a.k.a sulfur bacteria formation) in the drain, but not in the water source. Bacteria formation in the drain can be caused by the accumulation of hair, dirt, food particles and soap in the drain, which sticks/clogs the pipes, and produces hydrogen sulfide gas (sewage-like smell) as they decay.

Clogged or poorly maintained drain can cause hydrogen sulfide gas
Clogged or Poorly Maintained Drain

The easy way to accurately determine the presence of sulfur bacteria (hydrogen sulfide gas) in the drain and not the water source is by filling a glass cup with water from the sink/faucet, then take it to another room, swirl it a couple times, and smell it again. If the smell is gone, then it confirms the presence of hydrogen sulfide gas in the drain.

Bacteria and H₂S in the drains can’t contaminate the water, so they aren’t a health threat. However, having sinks that produce bad smells can be quite cumbersome.

2. Sulfur Bacteria Formation Inside the Water Heater

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

Sometimes when you don’t use hot water for a period or leave the thermostat of the water heater at low degrees, it creates an environment for bacteria to thrive. In the end, they release a potent stench that can be mistaken for sewage.

Additionally, water heaters mostly feature a sacrificial anode made of magnesium or aluminum installed inside their water tanks. They protect the tank by attracting mineral buildup and corrosion, hence why they’re “sacrificial”.

However, when magnesium and aluminum react with sulfur in the water, the end result is the production of hydrogen sulfide gas that can contaminate water if the anode rode in the water heater corrodes.

Corroded Magnesium Anode Rod in Water Heater Can Cause Rotten Eggs Smell
Corroded Magnesium Anode Rod in Water Heater

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

If only the hot water is smelly, then the problem lies within your water heater. If both glasses smell, on the other hand, the problem is likely to be at the water source.

You can determine if the sacrificial anode or bacterial activity is the source of the smell by opening up the water tank and checking if the anode is corroded. If it is, that’s the root of the smell; if it isn’t, then bacterial activity is the likely culprit.

3. Sulfur Bacteria Has Contaminated the Water Source

There are two water sources: municipal water supply (also referred to as tap/city water) and private wells. The chances that a municipal water supply can be contaminated by hydrogen sulfide bacteria is quite low since city water is regularly treated with chlorine and chloramines by the respective water authorities. However, the same can’t be said for private wells.

Quite the opposite, wells can sometimes be the breeding ground for hydrogen sulfide bacteria. This is especially the case in areas where the groundwater is rich in sulfur.

Additionally, without the bacteria, the hydrogen sulfide itself can also end up in the water source through surface water runoff or as a result of decay in soil and rocks where the groundwater is.

Spring Water Source That Smells Like Rotten Eggs
Spring Water Source That Smells Like Rotten Eggs

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. Although H₂S in drinking water is deemed safe by authorities, you shouldn’t overlook other potential water contaminants.

How to Remove Rotten Eggs Smell in Water

  • If sulfur bacteria accumulation in the drain is the source of rotten eggs smell, 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. After 10-15 minutes, flush it down with hot water. Also, make sure you don’t get any bleach in your eyes or on your skin.
  • If the smell is the result of corroded anode rode in water heater, you must remove or replace it. Note that removing the anode may reduce the lifespan of your water heater tank since the anode protects the tank from corrosion. If you replace it, make sure to regularly check it to prevent further recurrences of smelly hot water.
  • If there is sulfur bacteria accumulation in the water heater, you need to disinfect and thoroughly flush the heater. To disinfect the heater, turn off its water, power, and gas supply, pour a gallon of bleach into it through its hot water outlet, and reconnect the hot water line. Then, run all the hot water faucets at your house until you smell bleach. When you can smell it, turn off the faucets and let the bleach stay inside the system for at least a day. In the last step, turn on 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 the water well, you need to thoroughly disinfect the well by shock chlorination. Also consider purchasing a sulfur water filter for well water to to filter the water after the shock chlorination process.
  • If the water well is contaminated by hydrogen sulfide, you should contact professional well contractors. They’ll assess if there’s any damage in your well casing and offer you solutions. If there’s no damage, the root is probably the groundwater source, and you need a whole house filtration system with a reverse osmosis membrane and an ultraviolet filter.

Earlier on, we mentioned that city water is not likely to be contaminated by hydrogen sulfide since it is regularly treated with chlorine and chloramines. This doesn’t mean that the water can’t get contaminated, and you should immediately contact your water supplier if the lab analyses show the presence of hydrogen sulfide gas (H₂S) in the water.

Chemical, Medicinal, or Bleach-Like Smell in Water

Over-chlorination (excess amount of chlorine in water) gives water a chemical, medicinal, or bleach-like odor reminiscent of swimming pools. When chlorine molecules interact with organic properties like bacteria, fungi, and algae, they produce a certain 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, however, the chlorine concentration can reach 5 ppm in cases where the water is excessively contaminated and needs to be treated more severely than usual. When there’s such an excessive amount of chlorine in the water, it’ll inevitably emit a strong bleach-like odor in the house.

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

Chlorine in Water Causes Bleach-like Smell

How to Remove Bleach-like Smell in Water

The solutions very depending on the severity of the situation and your water source.

In cases like the shock chlorination of a well or the whole water system, the bleach smell can be removed by letting water flow from the faucets for a couple of minutes since chlorine evaporates when subjected to air. If this solution doesn’t work, then the other option is to flush the well, which will require the services of a professional contractor.

In the case of municipal city water supply, get in touch with your water supplier for appropriate guidance or consider one of the numerous methods to remove chlorine from water such as installing a reverse osmosis or whole house filtration system.

Water Smells Like Gasoline

If your water smells like gasoline or fuel-like, it likely indicates the presence of volatile organic compounds (VOCs) in the water supply.

Gasoline smell is also likely due to the following reasons:

  • A fuel or underground fuel tank leak near water source, specifically if the water supply comes from a well.
  • Fuel or gasoline contaminates the water supply due to landfills or factories nearby.
  • Agriculture discharge contaminates the water supply.

That said, the gasoline smell in your water can’t be resolved independently. You should stop consuming the water and immediately contact your water supplier or seek advice from professional water well service contractors if you have a private well.

Fishy or Musty/Moldy Smell in Water

Water smelling fishy or moldy often indicates the presence of chloramines, barium, or radium in the water. Decaying organic matter in the drains is also another possible source of the fishy smell.

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 cup of water, take it to another room, and swirl it a couple of times. If you no longer perceive the smell, then it confirms that the smell likely originates from decaying organic matter in the drain.

Fishy Smelling Water
Fishy Smelling Water

How to Remove Fishy Smell in Water

Chlorinating and flushing your drains is the best way to remove fishy smell caused by decaying organisms.

However, if the fishy smell is caused by chloramines, radium, or barium in your water, then you should consider installing a water filtration system to filter these contaminants.

Frequently Asked Questions

Can I prevent the sulfur smell from occurring?

Yes, sulfur-like smell in your water can be prevented by constantly cleaning/maintaining your drain, and installing a whole house water filtration system to filter your water. You should also occasionally check and maintain your water heater to prevent the sacrificial anode rode from corroding.

How much does it cost to get rid of rotten eggs smell in water?

This depends on the source of the rotten eggs smell. Chlorinating the drains or the water costs around $50. Shock chlorinating a well, however, can cost up to $100, depending on the depth and width of the well. Anode rod replacement for water heater can cost in excess of $150, minus labor cost. Should you decide to install a water filtration system, expect to spend $300+ depending on the brand and bathroom size. Lastly, if your well is contaminated due to damage to the well casing, you may need to have it repaired. A PVC well casing costs $6 per ft, while a stainless steel one is $130 per ft.

How long does it take for the sulfur smell to go away?

If your water has been treated for hydrogen sulfide, it takes about three days for the smell to completely disperse, as that’s how long it takes for hydrogen sulfide gas to fully break down.

Is rotten eggs water safe to drink?

Typically, water that smells like rotten eggs is safe to drink in small quantities. However, extended exposure may lead to trouble breathing, especially for individuals with a pre-existing condition, like asthma.

Is it OK to bathe in sewage-smelling water?

It depends on the source of the sewage-smelling water. If the smell is from a clogged drain, then it won’t do you any harm to take a shower. However, if it’s due to a bacteria build-up in your water heater, bathing could give you some nasty skin conditions from the contaminated water, including a particularly unpleasant rash called “hot tub rash.”

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Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
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