How quickly hot water must be restored
A landlord must restore hot water within a reasonable time after being notified, and because hot water is essential, that usually means quickly — often within a day or a few days, not weeks. A long outage can be a habitability violation.
There is no exact deadline in the law, but "reasonable" shrinks for something as basic as hot water. A short delay to make a repair may be understandable, while days or weeks without hot water — especially after you reported it — generally is not. The seriousness grows in cold weather or for households with children, older adults, or medical needs.
Report the problem in writing and keep track of how long you have gone without hot water, since that record matters if the landlord drags things out. If your landlord is stretching a hot-water repair well past a reasonable time, a free review can help you understand your options.
This is general information about California tenant rights, not legal advice. Every situation is different.