SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

The problem with drain valves in a northern-climate sprinkler system is that they are not necessarily going to get installed in the correct locations, when the pipes are installed without digging trenches. Pipe that's pulled into the ground with a vibratory plow does not lay at one level of burial depth. The plow blade might have to rise over rocks or tree roots, and the pipe level moves with it, and in doing so, create multiple low points in need of drains.

Better to stick with blowing out the system, especially since any backflow preventer might need some winterizing done for it, as they are not designed to require zero attention in every instance.