Between three and five feet off the ground is the optimal height for mounting a hose reel on an outside wall. The reel should be mounted above the hose spigot, near enough to provide the leader hose plenty of leeways to reach from the spigot to the water connector on the reel drum. For most users/homeowners, three to five feet off the ground is roughly waist to chest height, making it easy to handle and giving you enough power to reel the hose back up once you're done watering or gardening.