California Code, Public Resources Code - PRC § 16051

(a) A grease waste hauler shall not remove grease from a grease trap or grease interceptor unless the hauler removes all grease, greasy liquid, water, and solids from the grease trap or grease interceptor each time of removal.

(b) Subdivision (a) does not require a grease interceptor or grease trap to be cleaned of de minimus residue that cannot be removed by normal procedures, including, but not limited to, pumping or other cleaning, or residue resulting from systems that have continuous flow.