I have a bathroom with a drop ceiling which I want to raise back up to
8'. Before I can do this I need to move a drain waste pipe above the top sill plate of the wall. Currently, the pipe leaves the wall on a
45 degree angle about a foot below the roof. If I raise the vent pipe I'm not sure if I have enough room to keep the 45 degree angle. I would have to put a 90 degree elbow on the pipe. Can you have a 90 degree elbow on a drain waste vent pipe?