Internal drainage - this is in my option the only way to set up you rockers that pass through the wall to the inspection chamber. In the 15 years of doing drainage I’ve only ever come across two other gangs that do it the way I was taught. Often you’ll see people run the pipes out of the rat holes, concrete them in and then connect the inspection chamber up when it comes to do the external drainage. The issue with this is unnecessary bends are used and the pipes are laid to the incorrect falls d