Section 6(d) in The Chennai Metropolitan Water Supply and Sewerage Board's Sewerage Regulations, 1988
(d)Exclusion of rain water and salt: Every inlet to the sewer conveying waste water sullage or sewage shall be so located at such a level as to prevent storm water entering the sewer. No inlet or connection in any form to the sewer, for purpose of draining surface or subsoil water shall be permitted.
