How Do You Blow Out a Sprinkler System for Winter?
Blowing out a sprinkler system clears water from the pipes and sprinkler heads before winter. If that water freezes, it can crack pipes and damage valves, fittings, and other parts of your irrigation system.
Because using compressed air can be dangerous and damage equipment if done incorrectly, it’s best to have a qualified irrigation professional handle the blowout.
How to Blow Out a Sprinkler System: 7 Steps for Winterization
To blow out a sprinkler system safely, prepare the equipment, shut off the water supply, connect an appropriately sized air compressor, and clear each irrigation zone individually.
Follow these steps to understand the process, identify the equipment involved, and know when to call a professional.
1: Gather the Equipment for Blowing Out a Sprinkler System
Before blowing out a lawn sprinkler system, gather the right equipment and check your system’s air pressure and airflow requirements. Using the wrong compressor or fittings can damage your system or cause injuries.
- Air Compressor: Choose a compressor that can supply the required cubic feet per minute (CFM) at a pressure appropriate for your irrigation system. Do not rely on the compressor’s maximum PSI alone, because sufficient airflow is essential for clearing water from the lines.
- Compressor Hose and Fittings: Use a compatible air hose and secure fittings that connect the compressor to the irrigation system’s designated blowout port. Never force a connection or use an improvised fitting that could detach under pressure.
- Personal Protective Equipment: Wear approved safety glasses and hearing protection when working around compressed air. Keep your face and body away from sprinkler heads, valves, and other components that could eject debris or fail under pressure.
2: Shut Off the Water Supply and Prepare the Controller
Shut off the water supply before connecting the air compressor. You’ll also need to prepare the controller and backflow preventer to protect them during winterization.
- Close the Main Irrigation Shutoff: Locate the dedicated valve supplying water to your sprinkler system and close it completely. If the system shares a water supply with other fixtures, confirm that you have identified the correct shutoff before proceeding.
- Disable the Irrigation Controller: Turn off scheduled watering or place the irrigation controller in rain mode, if available. This prevents the system from activating unexpectedly during winterization and can preserve your existing watering schedule.
- Prepare the Backflow Preventer: Follow the manufacturer’s winterization instructions for your specific backflow assembly before applying compressed air. Backflow devices may require separate draining and valve adjustments, and some assemblies can be damaged if exposed to improper air pressure.
3: Connect the Air Compressor to the Blowout Port
Find the fitting where you’ll connect the air compressor to your sprinkler system. It’s often located after the backflow preventer, but the exact location depends on your system’s setup and local requirements.
- Identify the Connection: Find the system’s designated blowout fitting or approved air-injection connection. If no suitable connection exists, have an irrigation professional determine where one can be installed without damaging the plumbing.
- Secure the Hose: Attach the compressor hose using the correct fitting and verify that the connection is secure before introducing air. Keep people clear of the connection and nearby irrigation components throughout the process.
- Regulate the Air Pressure: Use a regulator and follow the lowest applicable pressure limit specified by the sprinkler, valve, pipe, and fitting manufacturers. Never assume that a system can tolerate the compressor’s full output, and do not exceed any component’s rated limit.
4: Set the Compressor Pressure and Airflow
Use the right air pressure and airflow when you’re blowing out a sprinkler system for winter. Too much pressure can damage pipes, sprinkler heads, and valves, while too little airflow can leave water in the lines.
Note: There is no single safe pressure or compressor size for every irrigation system. Have a qualified professional determine the appropriate settings based on the installed components, pipe material, and system design.
System Component | Winterization Consideration |
PVC Piping | Use the manufacturer’s permitted pressure and airflow limits; excessive pressure can damage rigid pipe and fittings. |
Polyethylene Piping | Follow the pipe manufacturer’s limits and account for the system’s fittings and connected components. |
Sprinkler Heads and Valves | Use controlled airflow within every component’s rated limits to reduce the risk of damage. |
Air Compressor | Check both CFM and regulated pressure to ensure the equipment suits the system. |
5: Blow Out Each Sprinkler Zone Individually
Once the compressor is connected and set to the correct pressure, blow out each sprinkler zone one at a time. Be careful, because compressed air can shoot water and debris out of sprinkler heads at high speeds.
- Open One Zone: Activate a single irrigation zone using the controller or the appropriate manual controls, following the equipment manufacturer’s instructions. Never introduce compressed air into a closed system or open multiple zones indiscriminately.
- Introduce Air Gradually: Apply regulated airflow while monitoring the zone and its sprinkler heads from a safe distance. Never stand over a sprinkler head or valve, and stop immediately if you hear unusual noises or notice signs of component failure.
- Watch the Water Discharge: Observe the discharge from a safe location as water begins leaving the sprinkler heads. Stop according to the professional’s established procedure and equipment guidance rather than running the compressor indefinitely or waiting for prolonged bursts of air.
- Repeat for Every Zone: Close the completed zone and move to the next one using the system’s approved operating procedure. Continue until every zone has been addressed, without exceeding the equipment’s pressure or duty-cycle limits.
6: Drain the Backflow Preventer and Remaining Components
Blowing out the sprinkler lines may not remove all the water from the backflow preventer, exposed pipes, and other components. Drain and protect these parts separately to help prevent freeze damage.
- Drain the Backflow Assembly: Follow the manufacturer’s instructions for shutting off the relevant valves, opening test cocks, and draining trapped water. Do not assume compressed air has cleared every chamber, since some backflow assemblies require specific handling.
- Check Low Points and Exposed Pipes: Inspect accessible low points, drain valves, and exposed plumbing for locations where water may remain. Use the installed manual or automatic drain valves as directed by the system manufacturer.
- Protect Vulnerable Components: Apply suitable insulation or an approved protective cover where appropriate, without blocking required vents or drain openings. Insulation can reduce exposure to cold but does not replace proper draining and winterization.
7: Shut Down and Secure the System for Winter
Once you’ve blown out all the zones and prepared the other components, disconnect the compressor and set the system up for winter according to the manufacturer’s instructions. Check for any damage or remaining issues before temperatures drop below freezing.
- Disconnect the Compressor: Shut off the air supply and release pressure safely before removing the hose and fittings. Never loosen a pressurized connection or leave the compressor running unattended.
- Make Sure the System Is Shut Down: Keep the irrigation controller disabled or in its recommended winter mode and leave shutoff valves in the positions specified by the manufacturer. Follow the appropriate instructions for any backflow valves or drain ports that must remain open during winter.
- Inspect for Damage: Look for leaking fittings, cracked housings, loose connections, or other signs of damage caused during the process. Arrange repairs before spring startup so damaged components do not create leaks or operating problems.
Should You Blow Out a Sprinkler System Yourself?
Before winter sets in, make sure every irrigation zone, drain, and exposed component is ready for freezing temperatures.
If you’re unsure whether your system has been fully drained or your backflow preventer needs additional protection, have an irrigation professional inspect it before the first freeze. Taking care of these details now helps ensure your sprinkler system is ready for spring startup.
FAQs for Blowing Out Sprinkler Systems
When should you blow out your sprinkler system?
Blow out your sprinkler system before temperatures regularly drop below freezing, ideally while you still have time to schedule a professional if needed. Don’t wait until the first freeze is in the forecast, since frozen water can crack pipes, damage sprinkler heads, and cause costly repairs. If you live in an area with unpredictable fall weather, schedule winterization early to avoid getting caught by a sudden cold snap.
Can I blow out my sprinkler system by myself?
You can blow out your sprinkler system yourself, but hiring an irrigation professional is the safer option if you’re unfamiliar with the process. Compressed air can damage pipes, valves, and sprinkler heads or cause serious injuries if you use the wrong equipment or pressure settings. A professional can determine the correct airflow requirements, clear each zone, and make sure the backflow preventer and other components receive the proper winter protection.
What size air compressor do I need to blow out a sprinkler system?
The right air compressor depends on your sprinkler system’s pipe size, layout, and airflow requirements. Pay attention to the compressor’s cubic feet per minute (CFM), which measures airflow, rather than choosing one based on maximum pounds per square inch (PSI) alone. You also need a regulator to keep pressure within the limits of your system’s pipes, valves, and sprinkler heads. Check the manufacturer’s specifications or consult an irrigation professional to determine the appropriate equipment and settings for your system.
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