Why would it be dangerous?
As I said, the DIY l-shape waste pipe is just extending the inner part thru which the exhaust flume is already exiting.
The exhaust is already outside the house.
The outer casing hence the air intake part of the flue is not being touched, so should continue to...
The exhaust plume from the central pipe section of my condensing boiler flue is continuously setting off the sensor of my outside security light.
The flue consists of 2 parts : first, a central pipe for expelling the boiler exhaust which extends beyond the 2nd part, an outer casing pipe...