Twin wall flue system design, calculating an offset

If the flue pipe has to move sideways to avoid an obstruction then this is called an offset. We will use bends and lengths to move the flue sideways and will need to know how far the flue has to move horizontally.



The offset distance is the horizontal distance from the centre line of the vertical flue before the offset, to the centre line of the vertical flue once the offset has been made. This is shown in the picture.