Lingering sewage smell is never a good sign within the house, let alone the restroom. The bad news is that any number of things can cause the sewage odor in your bathroom, and it can be difficult to pinpoint the source. The methane in sewer gas can be flammable in large quantities, and breathing it can be hazardous to your health. The good news is that once you identify the source, it’s often simple and inexpensive to correct.

The first possible cause of the sewage odor in your bathroom can be the fixtures. If they haven’t been used recently, the water in the P-trap has evaporated, removing the barrier between the bathroom and gases in the sewer system. The solution is to run water to fill up the P-trap again. If you smell the odor in a bathroom that’s being remodeled, cap any open drain pipes until your new fixtures are installed. If there’s still a sewage odor after running water down all the drains, or if you notice a sewage smell in a regularly used bathroom, check for leaks in or around the P-trap. Even a small amount of water leaking out of the bottom of the “U” can allow sewage gases to sneak in. Another possible cause is a clog in the drain.

Many assume that the toilet would be the culprit, but the water in the bowl acts as a smell barrier. If the bowl doesn’t fill up as it should, the problem could be a broken seal. It may be time to call United Water Restoration Group, Inc. The smell can be coming from an outside source: either a roof vent blocked by a bird’s nest, leaves, or some other type of blockage. A vent pipe that’s been incorrectly installed or cut can send odors into your home. A cracked vent pipe can be even harder to see, since the break may be hidden within the walls. A plumber can locate a vent pipe leak with a smoke machine, which fills the drain system with a harmless visible smoke.