Generally, there is no problem with installing your washing machine in the garage. In fact, the concrete floor is perfectly suited to an appliance that may leak a little water here and there. However, before you decide to install the machine in your garage, ensure that the area has a drain, hot and cold water supply, and will not fall victim to frozen pipes during long periods of cold weather. Once these requirements are satisfied, the garage works as good as any other room.
Your washing machine requires a supply of both hot and cold water to carry out all cycles. To ensure a good flow of water pressure, the trip the water travels from tap to the washing machine should be short. Most hoses designed to do this job are only about 3 feet long, so consider this a goal for which to shoot. The best arrangement would be to locate it directly in front of water spigots.
Clothes can't be washed without water, and you can't run a washing machine without somewhere to send the water when the cycle is finished. This generally means that a drain running into the main plumbing system should be nearby. In the case of a garage, it's okay if the drain is across the room, as long as the pipe carrying away the excess water doesn't create a hazard to foot traffic or cars entering the garage. Avoid simply running a line outside through a door or window, as it may violate local ordinances for waste disposal.
To make the installation, clear a spot for the machine near the water taps. Check to make sure that you have an appropriate electrical outlet nearby, since most washers require 220 volts. Run a hose from the hot water spigot to the hot water inlet on the washer. Repeat the process with the cold water. Hook the drain line into place, turn on the water and you're ready to begin cleaning clothes in the garage. Don't forget to level the machine using the adjustable legs. Otherwise, a heavy, unbalanced load could send it creeping across the floor, breaking hoses and pipes in the process.
You can't wash clothes if your water pipes are frozen. A garage is usually less insulated than the rest of the house, and you'll need to consider this factor if you live in an area that experiences long, cold winters. Take proper precautions to ensure your pipes don't freeze in cold weather. In addition, don't leave any excess water in the washing machine for long in the dead of winter.