How to Blow Out Sprinklers for Winter

Blow Out Method

1. Shut Down and Drain the Water Line

   Begin the process of winterizing your sprinkler system by turning off the isolation valve to the sprinkler system to prevent water from the main line from flowing into the pipes. There will be a hose bib (small faucet) located after the isolation valve, either inside the home or outside before the backflow preventer. Place a bucket underneath this faucet, then open the hose bib to drain the water from the main sprinkler line.

2. Turn off the Timer

   Not all sprinkler systems run on a timer, but if your system does have a timer, then it's advised to shut it down. The reason for this is to help protect the timer and the sprinkler system by reducing the risk of electrical or mechanical faults throughout the winter.

   Some timers can also be set to rain mode, which tells the timer that it's raining and it doesn't need to come on. This allows the programming to remain unchanged, and when the spring rolls around again, you can simply turn off rain mode to resume your regular watering schedule.
   

3. Connect the Air Compressor

   In order to blow out the sprinkler system, you will need an air compressor that can produce air at a volume of at least 30 to 50 cubic feet per minute (cfm) and at pressures of 40 to 80 pounds per square inch (PSI).

   Close the airflow valves on the compressor and attach the air compressor to the irrigation system with an air compressor blow out adapter. These adapters are regularly used for winterizing RVs, so they should be relatively easy to find.

4. Open Sprinklers

   Even a powerful air compressor isn't capable of blowing out the entire system without risking damage to the pipes and sprinklers, so you will need to open each zone of sprinklers, one at a time, starting with the furthest zone. Opening the sprinklers provides a path for the air to travel and it will allow the water to escape instead of building up pressure inside a closed system.

   By starting with the farthest zone from the main line you can ensure that the entire irrigation system is adequately empty with a zone-by-zone blow out. The only exception to this is if the yard includes uneven terrain, like small sloping hills. In this case, start with the sprinkler zone that is on the highest level first.
   

5. Blow Out Sprinkler Line

   Begin the process of blowing out the lines by closing the backflow valves to help direct the flow of air in the opposite direction. With the farthest or highest sprinkler zone open, turn on the compressor and begin to add air to the sprinkler system. Slowly open the compressor valve, gradually adding additional air pressure as needed.

   When the pressure is sufficient, you should start to see water coming through the sprinkler head. The air pressure should not exceed 80 PSI for PVC piping or 50 PSI for polyethylene piping.

   Continue to blow water out of the sprinkler heads in the first zone until the spray of water ends, then open the next furthest or highest sprinkler zone and close the first zone. Move through each zone until all sprinkler zones have been blown out.

   Repeat this process at least one more time to ensure that all water has been blown out of the system, then turn off and disconnect the compressor.
   

6. Release Remaining Air Pressure

   Open and close the valves on the backflow preventer and on the manual drain valves to release any air pressure that is still remaining in the system, then close the valves to keep the sprinkler system isolated for the winter. The irrigation pipes and sprinkler heads should now be clear of any water, preventing them from freezing in the winter weather.

Manual Drain Method

There are some irrigations systems that come equipped with manual drainage, allowing you to empty excess water from the system by opening the drain valves.

1. Shut down and drain the water line: Start by turning off the isolation valve to the sprinkler system. Once this valve is closed, look for the hose bib or small faucet located down the line from the isolation valve. It can be either inside the home or outside before the backflow preventer. Put a bucket under the faucet and open the hose bib to start draining the water from the main sprinkler line.
2. Locate the manual drain valves: If you have drained the irrigation system before, then you should be familiar with the layout. For those that have never worked with the sprinkler system, look for manual drain valves at the ends of the piping, as well as any low points of the piping. You may need to raise the sprinkler heads to improve draining if the system is equipped with check valves. These valves only allow water to flow one way, so raising the sprinkler heads gives the water an additional outlet for draining.
3. Drain the system: Open all manual drain valves and raise the sprinkler heads, if necessary. Water should begin draining out of the sprinkler system. Use a set of channel lock pliers to gently loosen any valves that seem tough to turn. Also, make sure to drain the backflow device to prevent water from freezing and damaging the internal components of the backflow preventer.
4. Close all the valves: It may take several hours for all the water to drain out of the system after opening the valves. When no more water is draining from the valves, close all valves and lower any sprinkler heads to complete the winterization process.
   

Automatic Drain Method

Some sprinkler system manufacturers have started incorporating device to make the winterizing process more convenient. Auto drain systems have valves that automatically drain water from the pipes when the pressure falls below a specific number of pounds per square inch.

1. Shut down and drain the water line: Begin this task by turning off the isolation valve to the sprinkler system. Look for the hose bib or small faucet located after the isolation valve, then place a bucket under the faucet and open the hose bib to drain water from the main sprinkler line. Hose bibs are typically found outside before the backflow preventer, though they can sometimes be installed inside after the isolation valve.
2. Run one sprinkler head to relieve pressure: In order for the automatic sprinkler system to begin draining, you need to reduce the internal pressure. Do this by running one sprinkler head. Since the isolation valve for the system is closed, no additional water will be added to the sprinkler system, allowing the open sprinkler head to relieve the pressure throughout the water lines.
3. Wait for automatic draining to finish: Once the pressure drops below the specific number of pounds per square inch as indicated by the manufacturer, automatic draining should begin. The automatic drain valves will open, clearing the pipes of excess water. However, if the sprinkler heads are equipped with check valves, then you may need to raise the sprinkler heads above ground to drain them individually.
4. Close all the valves: Give the system a few hours to empty the remaining water. After confirming that the entire system is drained, close any valves to prevent water from entering the sprinkler system during the winter months.