Why no running water is an emergency
No running water is a serious habitability emergency in California. Report it to your landlord immediately, because a home without running water is not fit to live in, and the landlord must restore it quickly.
Whether the cause is a broken main, a plumbing failure, or an unpaid bill the landlord was responsible for, a total loss of water makes basic living — drinking, cooking, cleaning, and using the toilet — impossible. This is not a repair that can wait for days.
Report it in writing, note the time, and treat it as an emergency, using any emergency-maintenance line your landlord provides. If a landlord deliberately shut off your water, that raises separate and serious legal problems. If you have lost running water and your landlord will not restore it, a free, confidential review can help you understand your options.
This is general information about California tenant rights, not legal advice. Every situation is different.