Branch pipes - sizing, bends and junctions

A branch pipe should be at least the same diameter as the appliance trap and where it serves more than one appliance and is unvented, it should be of at least the diameter and gradient given in Table 2.4. A bend in a branch pipe should have as large a radius as possible and never be less than 75 mm centre line radius. A junction on a branch pipe should be made either at 45º or with a minimum sweep of 25 mm radius. The connection of a branch pipe of 75 mm or more in diameter to a stack should be made either at 45º or with a minimum sweep of 50 mm radius. A branch pipe should discharge into a stack – (a) in a way which prevents cross-flow into another branch pipe (see Diagram 2.1); and (b) not less than the relevant height, above the invert level at the foot of the stack, given in Diagram 2.1.