Technical Booklet N Drainage·Page 19·3.2
Layout of drainage system
The drainage system should minimize changes of direction and gradient with access points at changes. Drains must be laid to even gradient in straight lines between access points, with large-radius bends in inspection chambers. Special precautions are required where drains run under or near buildings, and connections to sewers must follow NIW adoptive standards.
The system should have as few changes of direction and gradient as practicable, and access points (see paragraph 3.12) should be provided at such changes. Drains should be laid to an even gradient and in straight lines between access points (slightly curved drains may be acceptable in certain circumstances). Other than at the foot of the discharge stack (see paragraph 2.14) bends should have as large a radius as practicable and be in or adjoining inspection chambers or manholes. Where a drain runs under or near a building special precautions to accommodate the effects of settlement should be taken (see paragraph 3.9 and 3.10). Northern Ireland Water (NIW) controls the connection of a drain to a sewer, therefore any connection should be installed according to the adoptive standards in the NIW publication Sewers for adoption Northern Ireland - A design and construction guide for developers in Northern Ireland.
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