Swan-Neck Offsets: 60mm, 60-210mm & >210mm
Two 72 degree bends make a ‘swan neck’ to offset the downpipe from the roofline to the wall of the building.
● In the 80mm diameter downpipe 2 bends make a maximum of 210mm offset
● In the 100mm diameter downpipe 2 bends make a maximum of 255mm offset
● There is a 60mm fixed offset available in both sizes of downpipe
● For any other offset between 60mm and the maximums you should pivot the ‘swan neck’ inside the downpipe to whatever distance from the wall is required to meet the outlet at the roofline. So that the running outlet or prefabricated outlet is not directly above the downpipe but set off to the side as necessary.
● For even larger offsets, as in the case study in Aberystwyth, a cut section of downpipe can be inserted between the two bends, cut to what ever additional length is required
(N.B. remember to allow for the overlap of the swaged necks of the downpipe piece and of the the bends in your calculations).