Does your bathroom suddenly have a certain “rotten egg” smell? The most likely culprit is septic gas finding its way back into your home. There are many reasons gases from your septic system may be entering your home. No matter the cause, septic odors are a sign that something is wrong, and the issue should absolutely be addressed. Septic gas can be a complex mixture of both toxic and non-toxic gases, created during the breakdown of household waste held in the septic tank. Mostly composed of odorless methane, septic gases also contain ammonia, carbon dioxide, hydrogen, nitrogen, and sulfur dioxide. If concentrated in small areas, these gases can be dangerous. However, these gases are not harmful at the concentrations that usually exist when indoor septic odors are present.


Modern plumbing is designed to keep odors out of your home, so the presence of a septic odor inside your home is typically a sign that there is a problem somewhere along your plumbing line. An unpleasant odor could indicate any number of problems, but these are the most common.


Perhaps the most common cause for sewer gases inside your home is a dry plumbing trap. Traps are simple u-shaped bends in the plumbing, one end connected to the drainpipe and the other connected to the pipe leading out to the septic tank. Traps hold a small amount of greywater, which prevents odors from coming back up the pipes from the septic tank. When these traps dry out, septic gases are able to flow back up through the plumbing, and the result is a foul odor inside your home. If you notice this odor in the bathrooms after coming home from a vacation, the water in your traps may have evaporated, and the issue can be solved by flushing water down all your home’s drains. If the odor is present even with regular plumbing use, another issue may be to blame for the odor inside your home.

Break in the Sewer Line

As homeowners, we tend not to worry about what goes on deep in our plumbing because once it is out of sight, it is out of mind. For the most part, that is a safe assumption to make. Modern plumbing systems are simple, but brilliant, in design. They work tirelessly to carry wastewater away from our home, often relying only on gravity and the flow of water to keep our pipes clean. Breaks in the sewer line do happen, however, and the most common sign is an odor of sewer gas inside the home. Sometimes this odor will appear near drains, such as in the bathroom or the kitchen. Other times the odor will be most potent in the basement or crawlspace, where wastewater may be collecting due to a leak.

Vent Stack Clog

Some of the most easily forgotten components of a home’s plumbing system are the vents. Through a system of pipes that exit through a home’s roof, plumbing vents work to regulate air pressure within the system and remove gases and odors common to a household’s plumbing system. When these become clogged, whether from falling debris or from birds building a nest inside the pipe, the plumbing system acts up in strange ways. Common issues associated with a vent stack clog include slow draining sinks or toilets, “ghost flushing” toilets, or sewer gases collecting within the home, especially in bathrooms and kitchens. These symptoms are also commonly associated with an overfull septic tank. Because identifying and clearing a clog in a plumbing vent can be difficult, and sometimes dangerous, we recommend eliminating the other common causes for indoor septic odors before investigating whether a clogged vent stack may be to blame.

Overfull Septic Tank

Next to dry drain traps, an overfull septic tank is the most common reason for septic odors appearing inside the home. Often these odors, if left unaddressed, will precede a sewage backup because they are a warning that the system is becoming overwhelmed. Other telltale signs of an overfull septic tank include gurgling drains, slow or sluggish drains, and finally, sewage coming back into the home through shower and sink drains. Depending on the number of people living in your household and the type of use your system gets, the average septic system will need to be pumped every 2-3 years.

If you start to notice a septic odor in your home, our first recommendation is to flush the drains to ensure none of the traps are dry. If the odor persists or gets worse after that, it is time to give us a call to schedule a service visit. If the problem continues even after your septic system has been serviced, it may be time to call in a plumbing professional to address a more significant problem.

Do you think an overfull septic tank may be to blame for your indoor septic odors? Contact us today to schedule a service visit.

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