In my house, a sewage smell from a seldom-used bathroom sink used to put bleach at the top of my list. The thinking was simple: if something down the drain smells bad, pour something down there to kill it. As of mid-September 2026, with fall coming on, I know to check the trap before treating the smell as something bleach can solve.
That distinction matters here in California. In Riverside, City of Riverside Public Works says wastewater contains naturally occurring gases that can build up and create odors. At the bathroom sink, the question is whether the water meant to keep sewer gas out of the room is still in place. A bottle of bleach does not answer that question.
Next stepIf your bathroom sink still smells after running water, ask a plumber to check why the odor persists.Describe my sink odor→Free · Your number stays private
What USC Environmental Health & Safety says
USC Environmental Health & Safety puts it plainly: “A dried P-trap is the most common odor source in campus buildings.” That observation is about its campus buildings, not every bathroom in every house. But it identifies a straightforward possibility when a fixture sits unused and the odor seems to come from its drain: the trap may be dry…