(a) The requirements of this article shall apply to the construction, installation, arrangement, alteration, use, maintenance, and repair of all plumbing equipment and installations to supply water to, and dispose of sewage from, units, accessory buildings or structures and permanent buildings in all parts of the state.

(b) Existing plumbing construction, connections, and installations made before the effective date of the requirements of this chapter may continue in use so long as they were in compliance with requirements in effect at the date of their installation and are not found to be substandard.