Baxi 47 075 35 Installation & Servicing Instructions Manual page 27

NOTE: Horizontal flue pipes should always be installed with a fall of at least 1.5°
from the terminal to allow condensate to run back to the boiler.
page 21
8.2 Twin & Vertical Flue Systems
1. Maximum permissible equivalent flue lengths are:­
Vertical Concentric 10 metres 20 metres
Vertical Twin Pipe 15 metres
2. Any additional "in line" bends in the flue system must be taken into consideration.
Their equivalent lengths are:­
Concentric Pipes:
135° bend
93° bend
Twin Flue Pipe
135° bend 0.25 metres
(60/100) (80/125)
0.5 metres
1.0 metres