I have a question about sprinkler wiring. The sprinkler timer is located on the front wall of my house (this was done by the previous owner) and I should run a wire from there to a sprinkler valve located in the backyard. I was thinking of running the wire along the exterior wall, stapling it right below the roof. Then, when I read the articles of sprinkler wiring, most suggest to bury them under the ground. I am curious if it is ok to have over-ground wiring. The total distance is about 70 ft.