How to Drain a Residential Sprinkler System

Locate the main water line valve, which may be located in the basement or in a crawl space. If you're unable to find the main line valve, look outside of the home for water pipes near a wall. The main water line is usually just on the other side of the wall within the home and may or may not be labeled. If it's not labeled, locate the water meter; the main water line valve Ts off of the water meter.

Twist the main line water valve's control device until the valve is closed. If the main line valve is a gate valve, twist the knob to the right, until it's shut off. If the main line valve is a ball valve, grasp the lever and twist it from its parallel "on" position until the lever stands at a right angle to the main line in the "off" position.

Locate the main line drain valve, which is usually an open-ended ball valve just above the main line water valve. The main line drain valve might be a simple drain with a screw, which will require a screwdriver to open.

Place a bucket below the drain and twist the main line drain valve to the left to open it. Allow the water to drain into the bucket gradually. The draining process may require you to turn off the main line drain valve, empty the bucket and refill the same bucket. Allow water to drain until it's empty. Leave the bucket underneath the open drain, until the next time you restart your system.

Locate the backflow prevention device outside of the home, which is usually just on the other side of the main line valve. Identify the backflow prevention device by its blue handles and copper body.

Screw open the test cocks, which usually jut out of the side of the backflow prevention device and look like miniature ball valves, with a flat-head screwdriver. Insert the flat-head screwdriver into the screw of the test cock and twist the screw so that the screw divot is parallel with the test cock in the open position. Open both test cocks and allow them to drain.

Unscrew the bleed cap from the bleed at the bottom elbow of the backflow prevention device and allow the water to drain. Turn the blue handles of the larger ball valves until they are parallel with the backflow preventer, and allow them to drain through the bleed.

Close both the test cocks and ball valves of the preventer halfway and leave them like that, until you're ready to activate the system again.