What CFM and PSI should I look for in an air compressor for sprinkler blowouts?

For effective sprinkler winterization, aim for an air compressor that delivers 20-50 CFM (cubic feet per minute) at under 50 PSI (pounds per square inch). This combination provides sufficient air volume to clear the lines without causing damage. Never exceed 80 PSI on PVC piping or 50 PSI on polyethylene pipe.

What type of air compressor is best for blowing out a sprinkler system?

While various types can be used, gas-powered compressors are often recommended for their portability and lack of electrical reliance. Rotary screw compressors or reciprocating types with large air receiver tanks are also ideal. For small to medium-sized residential systems, portable electric air compressors can suffice.

What are the key safety precautions when using an air compressor to blow out my sprinkler system?

Always wear ANSI-approved safety eye protection to prevent injury from flying debris. Never stand over any irrigation components during the blowout process, and ensure air pressure (PSI) and volume (CFM) are controlled. Never blow air into a closed line or valve.

What is the basic procedure for blowing out a sprinkler system with an air compressor?

First, shut off the main water supply and disconnect any pressure sensors. Connect the air compressor to the blowout port, starting with the zone furthest from the compressor. Open the valves on the zone you are blowing out, turn on the compressor, and begin the blowout process until only a fine mist appears; repeat for each zone, and then drain the backflow preventer.

What kind of damage can occur if I use the wrong air compressor or improper techniques?

Using too much pressure can crack pipes, damage sprinkler heads, or even melt gears in the heads. Insufficient air volume can leave water in the system, leading to freeze damage. Incorrectly blowing out the backflow preventer can also damage its internal components, contaminating the water supply.

Sprinkler Blowout: Compressor Guide

By Home Sidekick Team June 16, 2025 9 min read 1782 words

air compressorsprinkler systemwinterizationirrigationDIYhome maintenance

Winterizing your sprinkler system is crucial for preventing costly damage from freezing temperatures. One of the most effective methods for winterization is the "sprinkler blowout," which involves using compressed air to clear water from the pipes. This guide provides a comprehensive overview of selecting and using an air compressor for this essential task.

Understanding the Sprinkler Blowout Process

Before diving into compressor selection, it's important to understand the sprinkler blowout process. Water left in your sprinkler lines can freeze, expand, and potentially burst pipes, sprinkler heads, and backflow preventers. A sprinkler blowout forces compressed air through the system, effectively pushing out any remaining water. While professional winterization services are available, performing a sprinkler blowout yourself can save money and provide peace of mind.

Why Use an Air Compressor?

An air compressor provides the necessary pressure and volume of air to effectively evacuate water from your sprinkler system. The key is choosing a compressor that meets the specific requirements of your system. Undersized compressors may struggle to clear the lines completely, while oversized compressors might deliver too much pressure, potentially damaging components. It is essential to understand what size air compressor you need to accomplish this task successfully.

Selecting the Right Air Compressor

Choosing the correct air compressor is essential for a successful sprinkler blowout. Several factors need consideration, including CFM, PSI, tank size, and portability.

CFM (Cubic Feet per Minute)

CFM measures the volume of air a compressor can deliver per minute. This is arguably the most critical factor for sprinkler blowouts. A higher CFM rating means the compressor can push more air through the system, ensuring thorough water removal. Generally, for residential sprinkler systems, a compressor delivering 4-5 CFM at 90 PSI is sufficient. However, larger systems with more zones or longer pipe runs may require a compressor with a higher CFM rating (6 CFM or more). Always check the manufacturer's recommendations for your sprinkler system.

Example: If you have a small yard with 4 sprinkler zones, a compressor with 4 CFM at 90 PSI should be adequate. For a larger property with 8 zones and extensive piping, consider a compressor with 6 CFM or higher.

Tip: It’s better to err on the side of a slightly higher CFM rating than necessary to ensure complete water removal, especially if you plan on using the compressor for other tasks.

PSI (Pounds per Square Inch)

PSI refers to the air pressure the compressor can generate. While volume (CFM) is more crucial for sprinkler blowouts, sufficient pressure is still necessary. Most sprinkler systems operate at a pressure between 30 and 60 PSI. Therefore, a compressor capable of delivering at least 90 PSI is recommended. This provides a safety margin and ensures the compressor can effectively push water through the lines, even if there are minor obstructions.

Caution: Exceeding the recommended PSI for your sprinkler system can damage pipes and sprinkler heads. Always use a pressure regulator to control the output pressure and prevent over-pressurization. Many sprinkler heads will be damaged or completely blown off at PSI levels exceeding 80 PSI.

Tank Size

The tank size of an air compressor affects how consistently it can deliver air. A larger tank provides a buffer, allowing the compressor to maintain a more consistent pressure and CFM. For sprinkler blowouts, a tank size of at least 6 gallons is recommended. This will give you enough stored air to handle multiple zones without the compressor constantly cycling on and off.

Practical Advice: Consider the size of your property and the number of zones when selecting a tank size. Larger properties benefit from larger tanks, while smaller properties can often get away with smaller tanks. If you have a very small system you can consider using portable compressors, but they should still have at least a 3 gallon tank.

Compressor Types and Portability

Air compressors come in various types, including pancake, hotdog, twin-stack, and stationary models. For sprinkler blowouts, pancake, hotdog, and twin-stack compressors are the most practical choices due to their portability. Stationary compressors are generally too large and cumbersome for this task.

Pancake Compressors: These are compact and lightweight, making them easy to transport. They are a good option for smaller properties with fewer zones.
Hotdog Compressors: Similar to pancake compressors but with a slightly elongated tank. They offer a good balance of portability and air capacity.
Twin-Stack Compressors: These feature two stacked tanks, providing increased air capacity compared to pancake and hotdog models. They are a good choice for larger properties with more zones.

Step-by-Step Sprinkler Blowout Guide

Once you've selected the appropriate air compressor, follow these steps to safely and effectively winterize your sprinkler system:

Gather Your Supplies: You'll need your air compressor, a hose adapter that connects your compressor hose to the sprinkler system's water supply line (usually a quick connect fitting), safety glasses, and potentially a wrench for tightening connections.
Turn Off the Water Supply: Locate the main water shut-off valve for your sprinkler system and turn it off completely. This is usually located in your basement, garage, or near the water meter.
Connect the Compressor: Attach the air compressor hose to the hose adapter and then connect the adapter to the sprinkler system's water supply line. Ensure the connection is secure and airtight.
Set the Pressure Regulator: Adjust the pressure regulator on your air compressor to the recommended PSI for your sprinkler system (typically between 30 and 60 PSI). Start with a lower pressure and gradually increase it as needed.
Open Sprinkler Zones One at a Time: Begin with the zone farthest from the compressor. Open the manual valve for that zone or use the sprinkler system controller to activate it.
Blow Out the Zone: Allow the compressed air to flow through the zone until water is completely evacuated from the sprinkler heads. This may take several minutes. You'll know the zone is clear when only air is coming out of the sprinkler heads.
Repeat for Each Zone: Repeat steps 5 and 6 for each zone in your sprinkler system, working your way from the farthest to the nearest zone.
Turn Off the Compressor and Disconnect: Once all zones have been blown out, turn off the air compressor and disconnect it from the sprinkler system.
Open Drain Valves (If Applicable): Some sprinkler systems have drain valves located at low points in the piping. Open these valves to allow any remaining water to drain out.
Inspect for Leaks: After the blowout, inspect the sprinkler system for any leaks or damage. Address any issues promptly to prevent further problems.

Safety Precautions

Safety is paramount when performing a sprinkler blowout. Always follow these precautions:

Wear Safety Glasses: Protect your eyes from debris that may be ejected from the sprinkler heads during the blowout process.
Do Not Exceed Recommended Pressure: Over-pressurizing the system can damage pipes and sprinkler heads. Always use a pressure regulator and stay within the recommended PSI range.
Stand Clear of Sprinkler Heads: Avoid standing directly in front of sprinkler heads while the system is being blown out, as they may eject water and debris at high speed.
Supervise Children and Pets: Keep children and pets away from the area during the blowout process.
Consult a Professional If Needed: If you are unsure about any aspect of the sprinkler blowout process, consult a qualified irrigation professional.

Troubleshooting Common Issues

Even with careful planning, you may encounter some issues during the sprinkler blowout process. Here are some common problems and how to address them:

Insufficient Airflow: If the compressor is struggling to clear the lines, ensure the CFM rating is adequate for your system. Check for any leaks in the connections and make sure the pressure regulator is properly adjusted.
Sprinkler Heads Not Clearing: If a particular sprinkler head is not clearing, try increasing the pressure slightly (within safe limits). You can also try manually opening and closing the valve to dislodge any debris that may be blocking the head.
Leaks in the System: If you notice any leaks during the blowout process, immediately turn off the compressor and address the leak. Small leaks can often be repaired with Teflon tape or pipe sealant.
Compressor Overheating: If the compressor overheats, turn it off and allow it to cool down before continuing. Overheating can be caused by prolonged use or insufficient ventilation.

Maintaining Your Air Compressor

Proper maintenance will extend the life of your air compressor and ensure it performs optimally for sprinkler blowouts and other tasks. Here are some essential maintenance tips:

Drain the Tank Regularly: Condensation can accumulate in the tank, leading to rust and corrosion. Drain the tank after each use to remove any moisture.
Clean the Air Filter: A dirty air filter can restrict airflow and reduce the compressor's efficiency. Clean or replace the air filter regularly, as recommended by the manufacturer.
Check for Leaks: Inspect the compressor for any leaks in the hoses, fittings, and tank. Repair any leaks promptly to prevent air loss and maintain optimal performance.
Lubricate Moving Parts: Lubricate the compressor's moving parts, such as the pump and motor, according to the manufacturer's instructions.
Store Properly: Store the compressor in a clean, dry place to protect it from the elements.

Alternative Winterization Methods

While using an air compressor is the most effective way to winterize a sprinkler system, alternative methods exist. These methods are generally less reliable and may not provide the same level of protection against freezing damage.

Manual Drain Valves: If your system has manual drain valves, you can open them to drain water from the pipes. However, this method may not remove all the water, leaving some vulnerable to freezing.
"Vacuum Breaker" Method: This involves using a shop vacuum to suck water out of the lines. However, this method is not as effective as using compressed air and may not be suitable for larger systems.

Note: These alternative methods are not recommended as the primary means of winterizing your sprinkler system. They should only be used as a supplement to a proper sprinkler blowout with an air compressor.

Conclusion

Winterizing your sprinkler system with an air compressor is a vital step in preventing costly damage from freezing temperatures. By selecting the right compressor and following the steps outlined in this guide, you can effectively remove water from your sprinkler lines and protect your investment. Remember to prioritize safety and consult a professional if you have any doubts or concerns.

Next Steps:

Evaluate your sprinkler system's specific requirements (number of zones, pipe length, etc.).
Research air compressor models that meet your needs in terms of CFM, PSI, and tank size.
Gather the necessary supplies, including a hose adapter and safety glasses.
Schedule a time to perform the sprinkler blowout before the first freeze of the season.