S.L. 10.11 Art. 16Underground drains

All underground drains shall be laid in straight lines, at an even gradient from point to point of not less than one to forty and, if constructed otherwise than of iron pipes, shall be completely embedded in and covered with good and solid concrete, at least fifteen point two centimetres thick, all round. Adequate means of access shall be provided in connection with such drains at suitable points in the open air.