N.J. Stat. § 58:12A-12
The owner or operator of each public community water system shall undertake the periodic testing of the water provided to customers by the system in order to determine the presence of hazardous contaminants, as identified pursuant to section 2 of this amendatory and supplementary act. A schedule for the periodic testing shall be established by the commissioner within six months of the effective date of this amendatory and supplementary act and pursuant to the "Administrative Procedure Act," P.L. 1968, c. 410 (C. 52:14B-1 et seq.). The tests shall be conducted during periods of representative demand by a laboratory certified by the department. The initial tests for the substances identified in subsection a. of section 2 of this amendatory and supplementary act shall be administered within 12 months of the effective date of this amendatory and supplementary act and semiannually thereafter, pursuant to the schedule established by the commissioner, unless the commissioner shall determine, on a case-by-case basis, that greater or lesser frequency of testing is necessary or sufficient to ensure the public health and safety. The tests for the substances for which maximum contaminant levels will be established pursuant to subsection b. of section 2 of this amendatory and supplementary act shall be conducted within one year of the effective date of this act and annually thereafter, unless the commissioner shall determine, on a case-by-case basis, that greater or lesser frequency of testing is necessary to ensure the public health and safety.
N.J.S. § 58:12A-12