Cal. HSC § 114133

(a) Except as specified in subdivision (b), copper and copper alloys such as brass may not be used in contact with a food that has a pH below six, such as vinegar, fruit juice, or wine, or for a fitting or tubing installed between a backflow prevention device and a carbonator. (b) Copper and copper alloys may be used in contact with beer brewing ingredients that have a pH below six in the prefermentation and fermentation steps of a beer brewing operation, such as a brewpub or microbrewery.