Section 19. Nothing in this chapter shall limit the authority of the department of telecommunications and energy to rule on the propriety of any rates charged by any public water system subject to its jurisdiction; provided, however, that in making such a ruling the department of telecommunications and energy may consider any fees required by registration adopted pursuant to section eighteen; and, provided further, that such ruling shall not impose any condition inconsistent with the provisions of any order issued by the department or the terms and conditions of a permit issued under this chapter or the regulations adopted hereunder. Compliance with any requirement imposed by the department of telecommunications and energy shall not exempt any public water supply systems from requirements of this chapter or the regulations adopted hereunder.