Paul A wrote:
I have to move a 1 1/2 vent pipe about two feet to allow room for a new
window. The pipe vents three sinks.
Is there anything wrong with using four 90 degree ells to run it to the
right, up, to the left and finally
rejoin the existing pipe to the roof?


That will be fine.
Note that the pipe will slope *upwards*, toward
the roof. That's built into the fitting, so you
shouldn't have a problem.

Jim