California Code, Civil Code - CIV § 1954.210

(a) If a tenant notifies the landlord of, or the landlord otherwise becomes aware of, a leak, a drip, a water fixture that does not shut off property,  1 including, but not limited to, a toilet, a problem with a water-saving device, or other problem with the water system that causes constant or abnormally high water usage, or a submeter reading indicates constant or abnormal high water usage, the landlord shall have the condition investigated, and, if warranted, rectify the condition.

(b) A tenant shall not remove any water fixtures or water-saving devices that have been installed by the landlord.

(c) If the condition is rectified more than 21 days after the tenant provides notice to the landlord or the landlord otherwise becomes aware of a leak, a drip, a water fixture that does not shut off properly, including, but not limited to, a toilet, a problem with a water-saving device, or other problem with the water system that causes constant or abnormally high water usage, or a submeter reading indicates constant or abnormally high water usage, pursuant to subdivision (a), the tenant's volumetric usage for any month or months that include the period between 21 days after the initial investigation and the repair shall be deemed to be fifteen dollars ($15) or actual usage, whichever is less.  At the landlord's option, if submeter readings are available to determine the usage at a point prior to investigation and a point following repair, usage shall be deemed to be fifty cents ($0.50) per day for those days between the two submeter readings or actual usage, whichever is less.

(d) If the condition remains unrectified for 180 days after investigation, no further volumetric usage charges may be imposed until the condition is repaired.

(e) If, in order to comply with subdivision (a), the landlord has provided notice pursuant to Section 1954, and the tenant has failed to provide access to the dwelling unit, then the charges shall not be determined pursuant to subdivisions (c) and (d).

(f) If the local water purveyor notifies the landlord of constant or abnormally high water usage at the property, the landlord shall investigate and, if possible, rectify the cause of the high water usage.