California Code, Health and Safety Code - HSC § 114240

(a) Wastewater tanks shall be of a capacity commensurate with the level of food handling activity.

(b) Wastewater tanks shall have a minimum capacity that is 50 percent greater than the potable water tanks. In no case shall the wastewater capacity be less than 7.5 gallons. Where potable water for the preparation of a food or beverage is supplied, an additional wastewater tank capacity equal to at least 15 percent of the water supply shall be provided.

(c) Additional wastewater tank capacity may be required where wastewater production is likely to exceed tank capacity.

(d) Where ice is utilized in the storage, display, or service of food or beverages, an additional minimum wastewater holding tank shall be provided with a capacity equal to one-third of the volume of the ice cabinet to accommodate the drainage of ice melt.

(e) Wastewater tanks on nonpermanent food facilities shall be equipped with a shut-off valve.