Okla. Stat. tit. 59 § 1015
Each city and/or incorporated town with a population of two thousand (2,000) or more in the state, having a system of water supply or sewerage shall, and any incorporated town, or any sewer district Commission may, by ordinance or regulation, prescribe rules and regulations for the material, construction, installation and inspection of all plumbing and sewerage placed in, or in connection with any building, structure, or conveyance in such city, town or sewer district, and the board of health or other proper authority of such city, town or sewer district shall further provide that no plumbing work shall be done, except in the case of repairing leaks, without permit being issued therefor upon such terms and conditions as such city, town or sewer commission shall prescribe.
Okla. Stat. tit. 59, § 1015