Soil Stack Design

L = 450mm, up to three storeys high
L = 740mm, up to five storeys high
L = one storeyheight, over five storeys 

Bends at the base of stacks should be of long radius. Two 45° bends may be used as an alternative. The same principle should be used for offsets.

The distance between the centre line of the lowest branch connection and the invert of the drain should be at least 450mm. 

Stub stacks

A group of ground floor appliances may be connected to drain using an unventilated stub stack. The vertical drop to the invert level of the drain must not exceed 1.5m from a WC and 2.5m from a waste appliance.