Section 46(5)(ii) in Punjab Urban Planning and Development Building Rules, 2018
(ii)Where the diameter of a drain is increased the crown of the pipes shall be fixed at the same level and the necessary slopes given in the invert of the manhole chamber, and in exceptional cases, where the required fall is not available, connection may be made upto half the difference in the diameter that is the connecting branch sewer shall be connected with the main sewer in such a manner that full supply level of both the sewers is maintained running half the diameter of both the sewers of drain and the minimum internal size of chamber (between brick faces) shall be as follows,-