Sewer Smell Coming From Under the Toilet

Rotten sewage-like smells coming from beneath your toilet might be caused by several problems. The smell can be tough to pinpoint because although it seems to be originating from under the toilet, the cause may not be located there at all. Getting rid of the sewage odor requires a careful inspection of your toilet and the floor beneath.

Damaged Wax Seal Ring

Broken wax rings are a common cause of sewer smells under your toilet.

One of the most common causes of a sewage smell coming from beneath your toilet is a damaged wax ring. If the toilet moves, rocking back and forth, or if it feels as though it sinks slightly when you sit on it, the wax seal ring at the base of your toilet may be damaged or missing. The wax ring provides a tight seal between the base of your toilet and the waste pipes, which prevents sewage gases from seeping up under your toilet.

Infrequent Use

Water in a toilet bowl will evaporate if the toilet is either not used or used only occasionally, which can result in a sewage smell because the sewer gas can come up through the empty trap, which keeps the gas underground where it belongs. Flush unused or infrequently used toilets at least once each week to keep traps full and sewer gases out of your toilet.

Dirty Rim

Organisms that usually live down inside the sewer can enter your toilet through the trap. Once inside, they hang around under the rim of the bowl, resulting in an odor that may seem to come from beneath the toilet. If the smell is stronger when you flush the toilet or during hot and humid weather, this may be the problem. To eliminate these organisms, open the tank on the back of your toilet and pour bleach into the overflow pipe of the flush valve, which will release the bleach around the rim and kill the organisms causing the smell.


If your toilet has a crack in the bowl, water can leak into the drain, lowering the water level in the toilet. These cracks are often caused by snaking a toilet too aggressively and may not always be visible, occurring on the inside of the toilet. When the water level is low, the trap is not filled, which enables sewer gas to escape, causing an odor to come up from your toilet. The only way to eliminate the odor in this case is to replace the toilet bowl.

About the Author

Renee Miller began writing professionally in 2008, contributing to websites and the "Community Press" newspaper. She is co-founder of On Fiction Writing, a website for writers. Miller holds a diploma in social services from Clarke College in Belleville, Ontario.