Why Does My Water Smell Like Sewage?

If your tap water starts to smell like sewage, it can be both off-putting and alarming. While you might wonder if you’re experiencing some kind of plumbing failure, a sewage smell in your drinking water is far more likely to be the result of bacteria or other organic contaminants lurking in your system.

To treat the issue, you need to identify the source and nature of the contamination, and apply the appropriate solution.

What causes sewage smell in water?

The most common reasons for tap water to smell like sewage are bacteria growing in your drain, bacteria growing in your water heater, or hydrogen sulfide in your water source.

To check the source of the smell, fill a glass with tap water, and step away from the faucet. After you’ve moved elsewhere, swirl the water in the glass, and sniff. If the water smells normal, the odor originates from the plumbing, not the water source.

Other telltale signs that the issue is in your plumbing versus your water source:
1. The smell is in the hot water tap but not the cold.
2. The smell goes away after you let the water run for a while.

Bacteria in your drain

If the water glass sniff test tells you the water itself smells normal, you probably need to clean your drain.

The most common reason for a sewage smell in tap water is sulfur-reducing bacteria feeding off of soaps and decaying food or other organic matter trapped in the drain. The odor produced by the bacteria is pushed out of the faucet when you turn it on, making you think it’s the water that smells rather than the drain.

Bacteria in your water heater

If you only notice the smell from your hot water tap, you should check your water heater.

The reason your plumbing smells like sewage could be bacteria growing in the water heater. If the water heater has been turned off for a long period of time (such as while you’re on vacation), or the thermostat on the heater is set too low, it provides a perfect environment for bacteria to grow.

Hydrogen sulfide in your water

If you’ve verified it’s the water itself which smells rotten, you’re most likely dealing with hydrogen sulfide in your water source. This would be most common in homes with a private well, rather than city water.

While hydrogen sulfide in your water supply is most often described as giving off a “rotten egg” odor, the egg smell is usually noted at 2 parts per million (ppm).

However, hydrogen sulfide can be smelled at levels as low as 0.5 ppm, and anything less than 1 ppm will smell musty, or like sewage.

How do you get rid of sewage smell in your water?

The solution to eliminating the sewage smell may be as simple as flushing out your drains or water heater, but some issues may require the installation of a water treatment system.

• Cleaning bacteria from drains

If you’ve verified the sewage smell is coming from your drain, cleaning it should resolve the issue. You can buy special organic waste drain cleaners, or try a home-made solution of baking soda, vinegar, and boiling water.

Drain cleaning directions: To disinfect your pipes and remove the odor, pour ½ cup of baking soda down the drain, followed by ½ cup of white vinegar, and wait 15 minutes. While the mixture is bubbling, bring a pot of water to boiling. After 15 minutes, pour the boiling water down the drain to flush it out.

• Cleaning out your water heater

If cleaning out your sink drain doesn’t eliminate the odor, you can try turning up the temperature on your water heater for 24 hours, and running hot water from your taps to kill and flush out the bacteria. Use caution to prevent accidental scalding from the hot water. Be sure to lower the thermostat and make certain the water temperature is reduced following treatment.

A note of caution: Always follow your appliance manufacturer recommendations. If you’re unfamiliar with your water heater operation or maintenance, you may want to contact a plumber for assistance and to assess if any parts need replacement or repair.

• Treating hydrogen sulfide in water

If the origin of the sewage smell is your groundwater, you may have hydrogen sulfide in your water supply. You will want to test your water supply to confirm the sulfate level, as well as assess if you have other issues such as iron, manganese, or bacteria that should be treated.

Your solution may include investment in a whole home sulfur reduction filtration solution to treat the water source.

Is water that smells of sewage safe to drink?

While water that smells of sewage is unappealing, it’s not necessarily a risk to your health. The foul odor and taste from sulfate-reducing bacteria or hydrogen sulfide usually inhibit consumption at levels well below those that would cause health issues.

However, sulfate may have a laxative effect that can lead to dehydration and is especially dangerous for infants. The Environmental Protection Agency (EPA) standard for drinking water sets the maximum contaminant level for sulfate to 250 ppm. Infants should not be given water with a sulfate concentration above 400 ppm.

If there is bacterial contamination in your water supply, it will probably need to be treated at the source.

A water test can determine the level of sulfate contamination as well as identify other issues.

There is not an EPA drinking water standard for hydrogen sulfide, because a concentration of hydrogen sulfide high enough for it to be a drinking water hazard would also make the smell and taste too unpleasant to drink. The level found in most household water is usually not a health risk, unless in very high concentrations, which is very rare. As hydrogen sulfide is a gas, it must be tested on-site.

Get rid of sewage smell in your tap water with proper treatment

When your drinking water suddenly smells like sewer water, identifying the cause of the issue is the key to figuring out the proper treatment solution. It’s always a good idea to test your water to make sure you identify and treat all the issues preventing your water from being clean and healthy.