When no hot water becomes an emergency
No hot water is usually treated as an urgent repair, and in some situations — like winter, or a household with medical needs — it can rise to an emergency the landlord should address right away.
While a total loss of water is a clear emergency, no hot water is at least an urgent problem that should not sit for days. How urgent depends on the circumstances: cold weather, infants, elderly or ill household members, or a complete loss of hot water all raise the stakes.
Many landlords keep an emergency-maintenance line, and a serious hot-water failure can be a fair reason to use it. Report the problem promptly, note the date and time, and describe anything that makes it especially pressing for your household. If your landlord ignores an urgent hot-water problem, a free review can help you understand your options.
This is general information about California tenant rights, not legal advice. Every situation is different.