Technical Booklet N Drainage·Page 17·2.14
Discharge stacks - diameter and installation
Discharge stacks must connect to a drain with minimum internal diameter per Table 2.5, must not reduce in diameter or have offsets carrying foul water, and must have a foot bend with a centre line radius of at least 200 mm. Stacks in buildings over 3 storeys must be located internally.
A stack should discharge into a drain and be of at least the internal diameter given in Table 2.5. The diameter of a stack should not reduce in the direction of flow, nor have an offset in any part carrying foul water. The bend at its foot should have a centre line radius as large as possible but not less than 200 mm. A discharge stack in a building over 3 storeys should be located internally.
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