Technical Booklet N Drainage·Page 13·2.7
Overflow pipes
Overflow pipes discharging to branch pipes or stacks must pass through a trap. In all other cases, they must discharge visibly and not cause dampness or damage to the building.
Where an overflow pipe discharges to a branch pipe or a stack it should do so through a trap. In all other cases an overflow pipe should discharge in a visible location and should not cause dampness in, or damage to, any part of a building.
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