Why does my bathroom smell like sewage or rotten eggs?

A strong sewage smell in a bathroom usually means sewer gas is getting into the room. Common causes include a dried-out P-trap on a sink, tub, or floor drain, a loose or failing wax ring under the toilet, or a venting issue in the drain system.

Start by running water for 20–30 seconds in all drains to refill the P-traps. If the smell is strongest around the toilet, the wax ring may be leaking and the toilet might need to be reset. If the odor is strong, constant, or you notice gurgling drains along with the smell, that usually means it is time to have a plumber inspect the sewer and vent lines. If the smell is more like natural gas, leave the area immediately and call 911.

Because sewer gas can be unhealthy and points to a drainage problem, it’s generally best to have a professional check it as soon as you can.