(1) Nothing contained in this chapter shall be construed as prohibiting the employment of an apprentice to assist a journeyman plumber in his duties.
(2) This chapter shall not apply to anyone who is employed or acts as a maintenance man.
(3) This chapter shall not apply to persons employed by any water company, water district or sanitation district, in the laying, maintenance, and operation of its mains and other appurtenances in the conduct of its business.
(4) The provisions of this chapter relating to the licensure of plumbers shall apply to all persons engaged in the practice of plumbing.