Walking into a clean bathroom and catching a foul sewer odor (hydrogen sulfide) is deeply unpleasant. Beyond the smell, sewer gas contains methane and bacteria that should never enter living spaces.
Cause 1: Dried-Out P-Trap in Seldom-Used Showers
The U-shaped curve under sinks and showers holds a water seal that prevents sewer gases from entering. If a guest bathroom or basement drain sits unused in dry Rialto weather for weeks, the water seal evaporates. Pouring 3 cups of water down the drain restores the seal instantly.
Cause 2: Failed Toilet Wax Ring
The wax gasket sealing the base of your toilet bowl to the closet flange can dry out or compress when the toilet rocks slightly. Sewer gas escapes around the porcelain base even if water does not leak onto the floor.
Cause 3: Blocked Rooftop Vent Stack
Plumbing vent pipes exit through your roof. If birds, leaves, or palm tree debris block the vent, wastewater rushing down drains pulls water out of nearby P-traps, releasing gas.