Spotting and reporting a hidden leak
A hidden leak behind a wall or under the floor is still generally the landlord's responsibility to find and fix. Warning signs include water stains, warped or soft walls and floors, a musty smell, bubbling paint, and an unexplained jump in the water bill.
Hidden leaks can cause serious damage before anyone sees water, quietly soaking framing and insulation and feeding mold inside the structure. Because locating and repairing a leak inside a wall or under a floor means opening things up, it is the landlord's job, not something a tenant should try to handle.
If you notice the warning signs, report them to your landlord in writing and take photos, even if you cannot see the leak itself. Describing the signs and the smell creates a record of when the landlord was notified. If your landlord dismisses clear signs of a hidden leak, a free review can help you understand your options.
This is general information about California tenant rights, not legal advice. Every situation is different.