What size air compressor do I need for blowing out sprinklers?

When it comes to maintaining your lawn sprinkler system, blowing out the lines before winter is an essential task. Doing so removes any remaining water from the pipes and prevents damage from freezing and bursting. To properly blow out sprinkler lines, most homeowners need an air compressor that can produce enough airflow and pressure. But choosing the right size air compressor for the job is key.

Blowing Out Sprinkler Systems

Blowing out a sprinkler system involves using compressed air to force all remaining water out of the pipes before freezing weather sets in. This prevents any trapped water from expanding as it freezes and rupturing the pipes. The process involves attaching an air compressor to the sprinkler system through a special blowout fitting or by using quick connect couplers. The air compressor is turned on and air is blown through the pipes, forcing the water out through sprinkler heads and valves.

For the blowout to be effective, the air compressor needs to produce enough constant pressure and volume of air to fully evacuate all water from the system. Too small of an air compressor may not have enough power to fully clear pipes of excess water. But too large of a unit is inefficient and wasteful.

Factors That Determine Air Compressor Size

There are several key factors that impact what size air compressor is needed to blow out a sprinkler system:

• Length of piping – Systems with more feet of pipes need higher airflow.
• Pipe size – Larger diameter pipes require more air volume.
• Number of zones – More zones means more airflow needed.
• Sprinkler head count – More sprinkler heads require a larger air compressor.
• Elevation changes – Systems with large elevation rises need higher pressure.
• Available CFM and PSI – The compressor must match system requirements.

Taking these factors into account will determine the optimal air compressor size for each sprinkler system.

Length of Piping

The overall length of the piping in the sprinkler system is a major factor. Longer pipe runs require greater airflow (CFM) to clear all the water. As a general guideline:

• Less than 10,000 ft of piping – Minimum of 30-50 CFM compressor
• 10,000 to 15,000 ft of piping – 50-80 CFM compressor
• Over 15,000 ft of piping – 80+ CFM compressor

Pipe Diameter

The diameter of the pipes used in the sprinkler system also impacts air needs. Larger pipes hold more water volume that needs to be displaced. Typical pipe diameters include:

• 1/2 inch piping – Requires 35-50 CFM
• 3/4 inch piping – Requires 50-90 CFM
• 1 inch piping – Requires 90-125 CFM
• 1 1/4 inch piping – Requires 125-170 CFM
• 1 1/2 inch piping – Requires 170-220 CFM

Number of Zones

Most irrigation systems are divided into zones based on areas of the landscape. More zones allow you to customize watering but require more airflow capacity to clear each additional zone line. General minimum CFM guidelines based on zones:

• 2-4 zones – 30-60 CFM compressor
• 5-7 zones – 60-80 CFM compressor
• 8-12 zones – 80-120 CFM compressor
• 12+ zones – 120+ CFM compressor

Sprinkler Head Count

The number of sprinkler heads in the system also increases air volume needs. Each head contains residual water that needs to be forced out by the air compressor. More heads means more airflow demand. Recommendations based on head count include:

• Less than 30 heads – 30-50 CFM compressor
• 30-60 heads – 50-80 CFM compressor
• 60-90 heads – 80-125 CFM compressor
• 90+ heads – 125+ CFM compressor

Elevation Changes

Significant elevation rises in the sprinkler system can also impact the size of air compressor required. More elevation change makes it harder to push water out, requiring higher air pressure (PSI). Some guidelines based on elevation include:

• Mostly flat terrain – 30-50 PSI compressor
• 10-30 ft elevation changes – 50-70 PSI compressor
• 30-50 ft elevation changes – 70-90 PSI compressor
• 50+ ft elevation changes – 90-125 PSI compressor

CFM and PSI Requirements

When selecting an air compressor, match its Cubic Feet per Minute (CFM) and Pound per Square Inch (PSI) ratings to your system requirements. A compressor with adequate CFM will provide enough airflow volume. And one with sufficient PSI will generate enough pressure for elevation changes and efficient blowouts.

Compressor Types for Blowing Out Sprinkler Systems

There are two main types of air compressors suitable for sprinkler blowouts:

• Gas-powered air compressors – These use a gasoline engine to operate and provide strong PSI and CFM. They are portable and do not require an external power source. Better for larger systems.
• Electric air compressors – These plug into an outlet and range from small pancake compressors to large stationary units. Electric compressors work well for smaller systems but may lack power for larger ones.

Within these types are air compressor designs optimized for sprinkler blowouts:

• Two-stage air compressors – Have two cylinders that allow more airflow volume at lower pressures for more efficient blowouts.
• Sprinkler blowout compressors – Specialized units designed specifically for winterizing sprinkler systems.
• High-volume compressors – Maximize airflow capacity measured in CFM for forceful blowouts.
• High-pressure compressors – Optimize PSI output to overcome elevation changes and pipe friction.

Air Compressor Size Recommendations

Here are some more specific air compressor size recommendations based on sprinkler system specs:

System Size	Compressor Type	Minimum CFM	Minimum PSI
Small (less than 10,000 ft piping)	Electric or gas powered	30-50 CFM	30-50 PSI
Medium (10,000 – 20,000 ft piping)	Electric or gas powered	50-80 CFM	50-70 PSI
Large (more than 20,000 ft piping)	Gas powered	80+ CFM	70+ PSI

These are just general guidelines. To determine your specific needs, evaluate all the factors of your sprinkler system carefully when selecting an appropriately sized air compressor for winter blowouts.

Portable Gas Air Compressors

For larger residential and commercial sprinkler systems, a portable gas-powered air compressor is often the best choice. Here are some top gas air compressor models capable of handling large blowout jobs:

NorthStar High-Pressure Portable Gas Air Compressor

• 158 PSI max pressure
• 73 CFM airflow capacity
• 6.5 HP Honda engine
• 150 ft hose capacity
• 2-stage pump design

Powerhorse Portable Gas Air Compressor

• 150 PSI max pressure
• 40.8 CFM airflow capacity
• 6.5 HP engine
• Low oil shutoff sensor
• Lightweight and easily portable

Generac SpeedAire Gas-Powered Air Compressor

• 125 PSI max pressure
• 70 CFM airflow capacity
• 7.5 HP engine
• Air tank capacity of 30 gallons
• Solid wheel kit for portability

These powerful gas air compressors provide the punch needed for completely blowing out high capacity sprinkler systems.

Electric Air Compressors for Small Systems

For residential sprinkler systems under 10,000 square feet, an electric air compressor often gets the job done. Here are some top electric models suitable for small blowouts:

DEWALT Pancake Air Compressor

• 165 PSI max pressure
• 6 gallon tank capacity
• 78 dBA noise level
• 16 foot power cord
• Weighs only 30 pounds

PORTER-CABLE Pancake Air Compressor

• 150 PSI max pressure
• 6 gallon tank capacity
• 82 dBA noise level
• 12 foot power cord
• Weighs 34 pounds

California Air Tools Ultra Quiet Air Compressor

• 120 PSI max pressure
• 10 gallon steel tank
• Only 60 dBA noise output
• Energy efficient 1 HP motor
• Weighs 49 pounds

For small residential systems, one of these electric units can provide sufficient airflow for a quick and quiet blowout.

Stationary Electric Air Compressors

Larger stationary electric air compressors are an option for big systems when portability isn’t needed. Here are some high-powered stationary models:

Industrial Air Two-Stage Electric Air Compressor

• 155 PSI maximum pressure
• 240 volt power
• 80 gallon air tank capacity
• 17 CFM airflow capacity
• Two-stage pump for continuous use

Ingersoll-Rand Single-Stage Electric Air Compressor

• 135 PSI max pressure
• 120 volt power
• 60 gallon air tank
• 21 CFM airflow capacity
• Splash lubricated pump

Quincy Two-Stage Electric Air Compressor

• 175 PSI max pressure
• 230 volt power
• 120 gallon air tank
• 25 CFM airflow capacity
• Low maintenance design

While less portable, these types of high-powered stationary electric air compressors are capable of winterizing even very large and complex sprinkler systems.

Rental Air Compressors

Another option is renting an air compressor specifically made for blowing out sprinkler systems. Many home improvement rental outlets offer specialty blowout compressor rentals on a daily or weekly basis. These units are powerful and optimized for winterizing all piping system sizes. Renting can make sense if you only need an air compressor once a year and don’t have space to store your own.

Conclusion

Choosing the right size air compressor is important for properly blowing out your sprinkler system before winter. Take into account the length and diameter of piping, number of zones and sprinkler heads, elevation changes, and required CFM and PSI. Smaller electric compressors usually work for systems under 10,000 square feet. For larger systems, a high-powered gas air compressor is typically best. And renting a specialty blowout compressor is also an option. With the right size compressor, you can effectively remove all water from your system to prevent freeze damage.