If you smell something nasty in or around your home, it might be sewer gas, and you may confuse it with some other smell. In this guide, you’ll learn what is sewer gas smell, how to know if it’s actually that, and what you can do about it.
What Is Sewer Gas?
Sewer gas is basically the nasty mix that comes out when bacteria chow down on sewage in places with no oxygen. That party of bacteria spits out gases like hydrogen sulfide, ammonia, methane, carbon dioxide, nitrogen, and hydrogen.
The real stinker here is hydrogen sulfide. That’s the one your nose catches right away. Ammonia can stink, too, but it barely shows up. The rest of those gases? There’s no smell.
Here’s how sensitive it gets. Hydrogen sulfide can be smelled at crazy tiny amounts. Think .001 parts per million. To give you a picture, one part per million is like one single inch stretched over nearly 16 miles. That’s how sharp your nose is with this stuff.
How Do I Know If It’s Sewer Gas?
If you smell something weird in your house, especially something that hits you like sewage, you gotta pay attention. That kind of odor usually means something’s wrong with your plumbing, and it’s not something to ignore.
Now here’s where it gets tricky. Sewer gas and natural gas both give off that rotten egg vibe, so your nose can get confused. But there’s a difference: natural gas has a sharper, skunk-like edge to it, while sewer gas leans more toward that raw sewage stink.
If you are unsure about it, use a reliable sewer gas detector.
A lot of people think that a carbon monoxide detector can do this job. However, a sewer gas leak won’t set it off. That’s because a CO detector is only made to sense one thing, which is carbon monoxide gas. It doesn’t react to hydrogen sulfide, methane, or any of the other gases in sewer gas.
So, if you smell a sewer odor in your house but your CO alarm isn’t going off, that doesn’t mean you’re safe. It just means the gas floating around isn’t carbon monoxide. Therefore, you need a detector that can detect all the gases in sewer smell.
What are the Main Causes of Sewer Gas Smell In a Home (With Fixes)
Here are seven sources of sewer gas smells around your house and the DIY fixes:
1. Septic Tank Vent
If you have a septic tank, it’s vented through the plumbing in your house. When that smell is vented into the air, the wind can carry it over your house and push it back down to the front or the back. That’s why you sometimes catch that sewer smell. It’s gross, but the fix is easy.
You don’t have to dig up the whole septic tank. There are usually two openings on it. Dig up the top opening that’s closest to the house or closest to the drain coming from the house. When you open it, you’ll see the drain pipe. It’s usually a four-inch line. Put a four-inch elbow on it, either a medium sweep or long sweep, and point it down so it breaks the water level about an inch. That stops the sewer gas immediately.
2. Floor Drain
Another common source of sewer odor is the floor drain. You might have one in a basement, a laundry room, or under a washing machine. If that drain has a trap, the water in it can evaporate, and when it’s dry, sewer gas sneaks into the house.
Every fixture has a trap, too, like the bathtub, shower, bathroom sinks, kitchen sink, and the washing machine. If you have a bathroom or fixture that doesn’t get used often, the trap dries out faster. For example, in a big house with several bathrooms, unused ones start to smell.
The simple fix is to run water for 5–10 seconds to fill the trap. If you never plan to use the drain, pour in non-toxic RV antifreeze. It won’t evaporate, so the trap stays sealed and stops the smell from coming back.
3. Toilet Flange
A really popular source of sewer gas smell is the base of the toilet. If the closet flange is below the floor level, it can cause problems. For example, after you remodeled your bathroom, the flange may have been set on the wood floor, then tile was added, which makes the floor thicker.
If the flange wasn’t raised, people often try stacking wax rings to fix it. That doesn’t create a good seal. You should never use more than two wax rings. One is usually enough.
The flange has to be level with the finished floor or a quarter inch above it. Since the flange itself is about a quarter inch thick, that gives it a good seal. If it’s not set right, sewer gas escapes. Many times, fixing the toilet seal solves the problem, even when you think it’s a cracked vent pipe or something bigger.
4. Cracked Drain Pipe
Older drain pipes, like cast iron, eventually wear out. Cast iron usually lasts about 30 years before it starts to decay. A crack in a pipe may not pour water everywhere. You might just see a wet spot on a basement floor or dampness near the base of a wall.
Even with a small crack, sewer gas leaks out. You can also get moldy smells if moisture lingers. To fix it, you need to cut out the bad section and replace it. In a basement, that’s fairly easy. Inside a wall, you’ll need to open it up to get to the pipe. Plastic lasts much longer and is usually the better option.
5. Neighbor’s House
Don’t always assume the sewer smell is from your house. Sometimes, the odor drifts over from a neighbor’s property. If their septic tank, sewer, or drain field has problems, you could smell it in your yard. So, always check nearby sources before tearing into your own plumbing.
6. Septic Tank Leak
If your septic tank or drain field has failed, you’ll often see water pooling around it. It’s also a major problem that releases a strong sewer gas smell. It’s also costly to repair, but it’s something that can’t be ignored.
7. City Sewer
In some older homes, plumbing vents are run on the outside of the house. When those vents rot or aren’t capped properly, they let out sewer gas. Remodeling sometimes leaves old vents dead-ended, which also causes leaks.
Plumbing code doesn’t allow dead-end pipes. If you find an old pipe like that, it should be removed or capped off properly. Otherwise, it can put sewer odors into your backyard or even into your basement.
Is It Safe to Stay In a House with Sewer gas?
Sewer gas is a cocktail of different gases. Some are harmless in small doses, but others turn toxic if they build up too much.
The main gas is hydrogen sulfide. It’s the one with the rotten egg smell. At high levels, it messes with your body’s oxygen system, which can result in serious symptoms, like organ damage or even death.
Then you’ve got ammonia. You already know it from cleaning products like Windex. In small whiffs, it stings your eyes, nose, and throat. In large amounts, it’s poisonous and can damage organs or be fatal.
Methane and carbon dioxide don’t hit your body as hard in small doses, but they’re still trouble. Methane, especially is highly flammable. Put that together with ammonia’s flammability, and now sewer gas isn’t just toxic; it can also be a fire hazard when levels get too high.
Conclusion
Now you know what sewer gas is, why you smell it, and how it affects your health. If the DIY fixes don’t work, it is time to bring in a professional from California Coast Plumbers to identify something bigger that is causing all these smells.