In operating under a permit under this section, the following standards and restrictions shall be met and complied with. No sanitary sewer shall be opened except by a licensed plumber and care shall be taken that no cement pipe or similar material shall be used in making connections. The connections shall be of such a length that they do not extend over four inches into a sewer "Y" or chimney. The trench from a main sewer to the property line shall be properly settled when back-filled. Upon discontinuance of oil operations or cancellation of the permit, the drain pipe shall be cut off at the property line and the connection cemented off.
(`78 Code, § 14.24.110.)