Things You'll Need
Tape or rope
Winter freezes can be highly damaging to a sprinkler system that isn't "winterized." Winterization of a system includes draining all water from the exterior pipes of your home. If water is left to freeze, it expands inside the system components, which causes cracks in the valves and pipelines. Pipe damage can lead to leaks outside and inside the home, not to mention a hefty repair bill. The backflow preventer unit is an important piece, which stops water from flowing back into the main water supply from outside. Before winter approaches, you'll want to protect your backflow preventer from harsh freezes by draining it.
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Locate the main water supply shutoff valve and turn it off. The valve is usually a gate or ball valve located along the main water supply line near the water meter inside in the basement or utility room of your home. Twist the gate valve completely clockwise or turn the ball valve from parallel to perpendicular to the main line to shut the main water supply off.
Place a bucket under the main drain valve of the main line, which is located near the main shutoff valve, and open the drain. Water flows from the drain into the bucket. Turn the valve off, empty the bucket, turn the valve back on and repeat until the pipe is fully drained. Leave the drain open over an empty bucket until the spring.
Locate the backflow preventer or pressure vacuum breaker, located on the outside of your home. Insert a flat-head screwdriver into the screws of the miniature ball valves, located on the side of the preventer. Twist each screw until the screw groove is parallel with the miniature ball valve in the fully open position.
Grasp the levers of the two larger backflow preventer ball valves and turn them parallel to the pipe or to the open position, if they aren't already in that position.
On the bottom elbow of the preventer, twist off the small drain cap and allow the water to drain completely from the preventer.
Twist the miniature ball valve screws and the two large valves of the backflow prevention device to a 45-degree angle after the preventer is fully drained.
Wrap the outside aboveground main lines and the backflow preventer thickly with towels and secure the towels with rope or tape. This will add a layer of insulation to further protect the preventer throughout the winter season.