How to Blow Out Sprinklers for Winter

Project Overview

• Working Time: 30 mins - 3 hrs, 30 mins
• Total Time: 1 - 4 hrs
• Skill Level: Intermediate
• Estimated Cost: $80

In-ground sprinkler systems are incredibly helpful for keeping your lawn and garden healthy during the warmer months, but when temperatures drop, the water inside the pipes can freeze and cause them to expand and crack. Rigid PVC pipes may burst entirely, while flexible polyethylene pipes are more likely to develop slow leaks.

Tip

This project describes one setup, but other types exist. Some irrigation systems have boxes in the ground with a reduced pressure zone to protect the local water supply. Note which type of setup you have before proceeding.

To help prevent damage to your sprinkler system, you need to shut off the water flow to the system and drain water from the pipes to keep them empty during the colder months. Learn how to blow out your sprinkler system to protect the lines from cracks and leaks.

Warning

Only attempt to blow out your sprinkler system if you have experience using an air compressor. An air compressor can cause extensive damage to the sprinkler system and pose a risk to an inexperienced user if the air pressure bursts the water line.

Blow Out Method

1. Shut Down and Drain the Water Line

   Start by turning off the isolation valve to the sprinkler system to prevent water from flowing into the pipes. Locate the hose bib (a small faucet) after the isolation valve, which may be inside or outside, before the backflow preventer. Place a bucket under the faucet and open the hose bib to drain the water from the main sprinkler line.

   

2. Turn off the Timer

   If your system runs on a timer, it’s advised to shut it down to reduce the risk of electrical or mechanical faults during winter. Some timers can be set to rain mode, allowing you to retain the programming and simply turn off rain mode in the spring to resume regular watering.

   

3. Connect the Air Compressor

   To blow out the sprinkler system, you need an air compressor that can produce 30 to 50 cubic feet per minute (cfm) and pressures of 40 to 80 pounds per square inch (PSI). Close the airflow valves on the compressor and attach it to the irrigation system with a blow out adapter, which is also used for winterizing RVs.

   

4. Open Sprinklers

   Open each zone of sprinklers one at a time, starting with the farthest zone. This creates a path for the air to travel and allows the water to escape. Starting with the farthest zone ensures the system is adequately emptied with a zone-by-zone blow out. In yards with uneven terrain, start with the highest zone first.

   

5. Blow Out the Sprinkler Line

   Close the backflow valves to direct the air flow in the opposite direction. With the farthest or highest zone open, turn on the compressor and begin adding air. Open the compressor valve slowly, gradually increasing air pressure. The air pressure should not exceed 80 PSI for PVC piping or 50 PSI for polyethylene piping.

   Continue blowing water out of the first zone until only air comes out, then move on to the next zone and repeat. Repeat the entire process at least once more to ensure all water is blown out, then turn off and disconnect the compressor.

   

6. Release Remaining Air Pressure

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

   

Manual Drain Method

Some irrigation systems come equipped with manual drainage, allowing you to empty excess water by opening the drain valves.

1. Shut down and drain the water line: Start by turning off the isolation valve to the sprinkler system. Locate the hose bib or small faucet after the isolation valve, place a bucket under it, and open the hose bib to start draining the water from the main sprinkler line.
2. Locate the manual drain valves: If you’ve drained the system before, you should know the layout. If not, look for manual drain valves at the ends and low points of the piping. Raise the sprinkler heads if your system has check valves that only allow water flow one way; this gives the water an additional outlet.
3. Drain the system: Open all manual drain valves and raise sprinkler heads if necessary. Use channel lock pliers to gently loosen any tough valves. Don’t forget to drain the backflow device to prevent internal damage from freezing water.
4. Close all the valves: Allow several hours for all the water to drain. Once no more water is draining, close all valves and lower any sprinkler heads to complete the winterization.

Automatic Drain Method

Some sprinkler systems come with automatic drainage, making the winterizing process more convenient.

1. Shut down and drain the water line: Turn off the isolation valve to the sprinkler system. Locate the hose bib or small faucet after the isolation valve, place a bucket under it, and open the hose bib to drain the main sprinkler line. Hose bibs are usually found outside before the backflow preventer, though they may be inside.
2. Run one sprinkler head to relieve pressure: Open one sprinkler head to relieve the system's internal pressure. Since the isolation valve is closed, no additional water will enter the system, allowing the open sprinkler head to reduce the pressure.
3. Wait for automatic draining to finish: Once the pressure drops below the specified amount, automatic draining will start. The valves will open, clearing the pipes of excess water. If the sprinkler heads have check valves, raise the heads above ground to drain them individually.
4. Close all the valves: Give the system a few hours to empty the remaining water. After confirmation that the system is drained, close any valves to keep water out during the winter.

FAQ

• What PSI do I use to blow out sprinklers?

  It’s a good idea to keep the PSI below 50 to avoid damaging the irrigation lines. However, you may use up to 80 PSI for thick PVC piping, while 50 PSI should be the maximum for polyethylene piping.

• How long should you blow out a sprinkler system?

  Generally, you should only spend about two minutes blowing out each zone. Ensure the lines are clear before moving on. You can move to a different zone once the spray of water turns to air.

• When should you blow out the sprinklers for winter?

  The goal is to blow out the sprinklers before the water in the lines can freeze. Winterize your sprinkler system before temperatures drop below 32 degrees Fahrenheit. Aim to get this done in early fall to ensure it’s ready before the cold weather hits.