What a persistent sewage smell signals
A persistent sewage or rotten-egg smell often means sewer gas is escaping into your home, usually from a plumbing problem — a dried-out or broken drain trap, a venting issue, or a hidden leak in a sewer line. It should be reported and fixed.
Sewer gas is not only unpleasant; it can be unhealthy and, in some cases, a safety concern. The smell may come and go, or be worse in certain rooms or at certain times. Common causes are a drain that has dried out from disuse, a cracked pipe, or a blockage — plumbing issues that are generally the landlord's responsibility to diagnose and repair.
Report the smell in writing and note when and where it is strongest, since that helps a plumber find the source. Do not just cover it with air fresheners. If your landlord ignores a persistent sewage smell, a free review can help you understand your options.
This is general information about California tenant rights, not legal advice. Every situation is different.