California Code, Health and Safety Code - HSC § 114309

(a) Mobile food facilities and mobile support units shall be exempt from the requirements of Sections 114250, 114256.1, and 114279.A local enforcement agency may exempt a push cart operating outdoors, other than a special purpose commercial modular and coach, as defined by Section 18012.5, or a commercial modular coach, as defined by Section 18001.8, that conducts only limited food preparation from Section 114149.1.

(b) This chapter does not require any person to replace or modify an existing mobile food facility approved for operation prior to adoption of this part, so long as the facility is operated in accordance with the conditions of approval. Plans and specifications may be required by the enforcement agency if it determines that they are necessary to assure compliance with this part.

(c) Mobile food facilities equipped with a one-compartment sink or two-compartment sink that was approved for operation prior to adoption of this part need not provide a three-compartment sink.