Smelling sewer gas can be unpleasant and even harmful—but fortunately, the problem is preventable and fixable
Sewer gas—largely composed of hydrogen sulfide—can smell like rotten eggs.
The presence of sewer gas in your home indicates there’s some sort of plumbing problem or failure, even if the smell comes and goes.
Low-level exposure to sewer gas can cause eye and respiratory irritation, but these symptoms should go away when you get away from the gas.
A local plumbing professional can help you assess the problem and find a solution.
Plumbing is one of those things where no news is good news: if your indoor plumbing is working well, it’s a flush-it-and-forget-it situation.
But sometimes, sewer smells can come back to haunt us—and even cause physical irritation. The good news? These odors are typically caused by leaks and clogs that are easy to prevent and are fixable with the help of a professional plumber. Here’s what you need to know.
If you catch a whiff of rotten egg smell in your house—and not because you haven’t taken out the compost in a while—you likely have a plumbing problem that needs attention.
The unpleasant smell is hydrogen sulfide, a gas that comes from decaying organic matter (the more polite term for raw sewage). Temporary, low-level exposure to some sewer gas can lead to eye irritation and respiratory issues that should go away when you get away from the gas. Here’s what you should do next.
Hydrogen sulfide is a colorless gas. Exposure to sewer gas can be dangerous, and can lead to eye irritation and respiratory issues like a sore throat and cough for all residents—including your pets. You don’t have to evacuate the premises, but maybe slide open a window or step away from the smell while you plan out your next steps.
Temporary exposure is typically not harmful, and the symptoms should go away soon after you step away. Long-term exposure to the gas, even at low levels, can have more dramatic symptoms, such as loss of appetite, fatigue, dizziness, and headaches. High levels of exposure would not be typical in a home.
But don’t delay fixing the problem. In addition to being unpleasant, sewer gasses, including hydrogen sulfide, are explosive. The best course of action is to get away from the smell and call a local plumber immediately and get the problem taken care of.
If you’re smelling hydrogen sulfide, it could be a minor problem like a dried-out water seal in a floor drain. Or you could have a blocked, broken, cracked, or deteriorated pipe allowing the gas to enter your home. Either way, it’s not going to go away until it's repaired.
In homes, hydrogen sulfide is directed out through vents. If you smell something foul, it’s a sign you have a plumbing problem that needs attention.
The smell is likely strongest at floor level or at the drain. While it might come and go (or you may become so used to it that you no longer notice it), it’s not fixed even if the smell dissipates for a while.
A professional plumber can diagnose the problem and recommend a fix, so everyone in the house can breathe easily again.
The most common cause of sewer gas smells in your house is a leak in your plumbing. You’ll want to prevent even small leaks to avoid major plumbing repair costs. Sewer gas smells could also be coming from your pipes if they weren’t installed properly or are damaged. A local plumbing professional can assess the problem and provide solutions, but here are some more common causes of septic odors in your home:
Ice buildup on plumbing pipes
Blocked vents due to landscaping
A broken septic pump
A full septic tank
A dried-out or leaky toilet wax seal
Clogged drains
All plumbing fixtures should have a sewer gas trap installed (just one of the few plumbing terms it’s helpful to know). This part allows wastewater to leave the house but blocks sewer gasses from getting in. Replacing one costs about $100 for materials and $45 to $200 per hour for a professional plumber’s time.
You can help prevent sewage smells by frequently running water in drains or faucets you hardly use, only flushing toilet paper and human waste, and ensuring you get your septic tank pumped every three to five years.
You can’t stop the ground from settling or the air from freezing, but you can take care of your plumbing. Keeping things flowing will prevent expensive backups and icky smells.
Watch what goes down the kitchen sink drain or gets flushed. Use the compost pail for food scraps, paper towels and cooking oils that can clog a drain. Use the trash can rather than the toilet for things like feminine hygiene products and dental floss. For about $10, you can get a hair trap for your shower drain, which will catch strands before they get caught in the pipes.
The average cost to have a professional clear a clog is $215.
If you have a rarely used bathroom or sink, the pipes can get dry. It helps to use your plumbing fixtures occasionally in between house guests. When you don’t use a fixture, the trap that keeps sewer gasses out can get dry. If the smell is coming from one drain or sink, run some water down it to see if that fixes the problem.
Even though you use your trash, compost pail, and hair catch, drains inevitably get backed up from soaps, lotions, detergent, beard trimmings, and whatever the kids put in there. If it starts to smell or the water drains slowly, you need to clean the drain. Most of the time, this can be accomplished by sliding a thin, flexible wire with a small hook at the end down the drain to grab the clog. You can buy a drain cleaning tool for about $5 at your local hardware store.
Candace Nelson contributed to this piece.
While a professional can always help, there are some common plumbing culprits you can check yourself to see if you can find the sewer gas smell. For example, you should check your water traps, sometimes called P-traps and S-traps, which are located under sink, shower, and laundry drains. The wax ring beneath the base of your toilet, which creates a watertight seal with the plumbing, could also have gone bad.
Sewer gas in any location can cause eye and respiratory irritation if you’re exposed at low levels, or more severe symptoms if you’re exposed at high levels—but fortunately, the fresh air outside means it’s less likely to affect your physical health. However, sewer smells outside can still indicate significant plumbing problems that will need to be dealt with, such as a potentially damaged sewer line or roof vent pipe.
It’s generally safe to stay in a house that smells like sewage, but you should get the problem fixed as soon as possible. In most cases, the level of sewer gas you’re exposed to in a home will be low enough to only cause minor symptoms, though high levels of gas exposure can be more dangerous. If you’re smelling sewer gas in your home, it’s important to locate, assess, and fix the problem, because it won’t go away on its own.
Symptoms of sewer gas poisoning include nausea, dizziness, extreme drowsiness, and headaches, according to the Wisconsin Department of Health Services. Exposure to higher concentrations for long periods of time could also lead to unconsciousness due to a lack of oxygen, aka suffocation. If you think you’ve been exposed to sewer gas for a dangerous amount of time, seek medical care immediately. Do not return to the site of exposure, after you’ve received medical care, call a pro for help.
