Cal. HSC § 116390

(a) No laboratory, other than a laboratory operated by the department, shall perform tests required pursuant to this chapter for any public water system without first obtaining a certificate issued by the department pursuant to Article 3 (commencing with Section 100825) of Chapter 4 of Part 1 of Division 101. (b) No person or public entity of the state shall contract with a laboratory for environmental analyses for which the state department requires certification pursuant to this section, unless the laboratory holds a valid certificate.