Technical Booklet N Drainage·Page 17·2.16
Unvented stub stacks - connection and height limits
Stub stacks may be unvented if they connect to a ventilated discharge stack or drain within 6 m. Branch pipes must not discharge into a stub stack above specified heights: 1.5 m from WCs or 2 m from other appliances.
A stub stack may be unvented if it connects to a ventilated discharge stack or drain and is not more than 6 m from the discharge stack or drain. No branch pipe should discharge into a stub stack at a height above the invert at the foot of the stack more than –
(a) 1.5 m where it is from a WC; or
(b) 2 m where it is from another appliance (see Diagram 2.6).
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