How quickly the landlord must respond
A California landlord must fix a water leak within a reasonable time after being notified, and an active, serious leak should be handled quickly — sometimes within a day or two — because water damage spreads fast and can lead to mold.
There is no single deadline in the law, but "reasonable" depends on how bad the leak is. A steady leak soaking the unit, a burst pipe, or an active roof leak during rain is urgent and should prompt a fast response, even after hours. A minor drip may fairly allow a little more time, though it should still be repaired.
Reporting the leak in writing and keeping copies helps establish exactly when the landlord's clock started. Note each report and any follow-ups. If your landlord lets a serious leak drag on well past a reasonable time, you may have several options, and a free review can help you decide what to do next.
This is general information about California tenant rights, not legal advice. Every situation is different.