Single Wall 1mm think stainless steel flue pipe is used to connect an appliance to either a chimney liner, stack or twin wall flue system. It can also be used to reline existing masonry chimneys. It is recommended that a verticle rise of 600mm should be allowed, immediately above the appliance before any change in direction. If bends are needed, then no part of a flue pipe should form an angle greater than 45° from the verticle, except where it may be necessary to use a very short horizontal section, not exceeding 150mm of flue to connect the flue pipe to a back outlet appliance. A maximum of 4 bends ( 2 offsets ) is permitted. Distances from combustible materials must be three times the diameter of the flue pipe. E.g. 150mm dm = 450mm clearance.