What’s that Smell? The Stench of Sewer Gas

October 17, 2021

Ever been in your kitchen, near the sink, and you catch a whiff of something horrid? You’re not sure where it’s coming from until you get closer to your sink drain. Is that rotten egg smell coming from your drain? That’s sewer gas.

Why Does it Smell Like a Skunk in the House?

It’s easy to get sewer gas confused with the smell of natural gas. Because natural gas is odorless, the skunk odor comes from a chemical called mercaptan that is added to the gas to help warn people of danger if they smell it.  So, if you smell something like a skunk in your home, you must call the local natural gas company immediately and evacuate the building if the odor is strong—a natural gas leak can lead to an explosion.

What is Sewer Gas?

Sewer gas is an odor that can come from your household’s septic or sanitary sewer system. It is mostly methane, which is odorless, but the odor comes from the methane mixing with other gasses such as hydrogen sulfide. Where does the hydrogen sulfide come from? It comes from decomposing organic matter (animal or vegetable).

The obnoxious odor mostly comes from what is called a “dry tap”—a sink, floor drain, or toilet that has not been used for some time. When the drain lays dormant, the water trap in the drain line dries out and the sewer gas then backs up into the room.

Another cause is when a broken drain line allows sewer gas into a crawl space, basement, or mechanical area, the it seeps into the house or apartment. Plugged or backed-up drains can also push the odor into the air.

Is it Dangerous?

While sewer gas is offensive, it can also be hazardous to your health if it’s present over any extended period. In a confined space, methane gas can displace oxygen and be deadly. The hydrogen sulfide is also toxic.

What can you do about sewer gas?

If you smell the rotten egg odor, first check for any dry traps and add some water to fill them.

If that doesn’t work, it might mean a broken sewer line, a vent that is plugged or not vented to the outdoors, a dead animal, or some other source of hydrogen sulfide. That’s when it’s imperative to call the professionals. Lindstrom’s plumbers can come out and pinpoint the source of the sewer gas and help clear the air.