Any distribution or transmission system constructed prior to the effective date of this chapter shall be given a test for leak in the manner prescribed in the ASA Code B31.1-1955 and state rules and regulations of the Washington Public Service Commission applicable to gas transmission and/or distribution utilities relating to the up-rating and increasing of pressure in existing mains. Wherever such ASA Code and rules and regulations relate to up-rating and increasing pressure in existing mains, they shall also apply equally where natural gas is introduced into existing mains which have previously carried artificial gas. [Ord. 4515 § 2, 2021; Ord. 1503 § 31, 1971; Code 1970 § 16.12.310.]