A backflow prevention device, also known as a check valve, is an essential element of a lawn sprinkler system. Each valve is situated on a pipe that leads to the valve and usually has a butterfly handle. To get the valves ready for winter, the handles should be turned perpendicular to the pipe, just like test faucets. When it's time to shut off the sprinkler system for the winter, it's important to do so gradually. The main water supply for your home is likely a large pipe that enters well below ground level, usually through a foundation wall.
This is not the sprinkler system valve. If the sprinkler system isn't closed inside the house, look inside the sprinkler system valve boxes around the yard. When it's time to turn on the sprinkler system again, make sure to do so slowly. This will guarantee that your lawn and garden get the water they need to become vibrant and lush.