How Blow out Sprinkler System? Blowout Method Explained

Introduction

For homeowners in cold climates, freezing winter temperatures pose a serious threat to underground sprinkler systems. When water trapped in pipes, sprinkler heads, and valves freezes, it expands, which can crack pipes, burst fittings, and cause thousands of dollars in costly repairs. If you’re asking yourself “How Blow out Sprinkler System?” to protect your investment before winter, this comprehensive guide will walk you through every step of the blowout method, explain why it’s the most effective winterization option, and help you avoid common mistakes that lead to system damage. The blowout method is the industry standard for cold climates, as it removes nearly 100% of residual water from your entire sprinkler system, eliminating the risk of freeze-related damage entirely when done correctly.

• What Is a Sprinkler System Blowout?
• Why Is Blowing Out Your Sprinkler System Critical?
• When Should You Perform a Sprinkler System Blowout?
• Understanding the Blowout Method
• Tools and Equipment You’ll Need
• Step-by-Step Guide to Blowing Out Your Sprinkler System
• Blowout Method vs. Alternative Winterization Methods
• Tips and Best Practices for a Successful Blowout
• Common Mistakes to Avoid
• Frequently Asked Questions
• Conclusion

What Is a Sprinkler System Blowout?

A sprinkler system blowout, also called air blowout winterization, is a process that uses compressed air to force all remaining water out of your sprinkler system’s pipes, risers, sprinkler heads, and control valves. Unlike manual draining, which only removes water from the lowest points of your system, the blowout method clears water from every part of the system, including high spots and individual heads where water is most likely to get trapped and freeze. This process is performed once per year, in late fall, before temperatures drop consistently below freezing. When done correctly, a blowout eliminates all risk of freeze damage to your sprinkler system over the winter months, saving you from expensive repairs and lawn damage in the spring.

Why Is Blowing Out Your Sprinkler System Critical?

Skipping the blowout process for your sprinkler system can lead to severe, costly damage, even if you only experience a few days of sub-freezing temperatures each winter. Water is one of the few substances that expands when it freezes, increasing in volume by approximately 9% as it turns to ice. This expansion creates immense pressure inside pipes and fittings, which can crack PVC pipes, burst polyethylene lines, break sprinkler heads, and damage zone valves. Even a small amount of trapped water is enough to cause damage: a single frozen section of pipe can leak hundreds of gallons of water when the system is turned on in the spring, leading to water damage to your lawn, landscaping, and even your home’s foundation if the pipe is located near the structure. Repair costs for freeze-damaged sprinkler systems range from $200 for a single broken head to $2,000 or more for full pipe replacement, making an annual blowout a small, worthwhile investment for most homeowners in cold climates.

When Should You Perform a Sprinkler System Blowout?

The ideal time to blow out your sprinkler system is 1 to 2 weeks before the first expected hard freeze in your area. A hard freeze is defined as temperatures dropping below 28°F (-2°C) for more than 3 consecutive hours, which is cold enough to freeze water in most sprinkler systems. Scheduling the blowout this early gives you time to continue watering your lawn if needed during warm fall days, without risking damage to the system if an unexpected cold snap hits. Avoid blowing out your system too early in the fall, as you may need to restart it to water new grass seed or drought-stressed lawns. Once you complete the blowout, you will need to shut off the main water supply to the sprinkler system for the rest of the winter, so plan accordingly if you still need to use the system for fall landscaping. If you live in a mild climate where temperatures rarely drop below freezing for extended periods, you may not need to blow out your system at all, but it is still a good precaution for unexpected cold snaps.

Understanding the Blowout Method

The blowout method works by using a portable air compressor to push high-pressure air through your sprinkler system, forcing all residual water out through the sprinkler heads. The process is performed one zone at a time, starting with the zone farthest from the backflow preventer (the point where you connect the air compressor) to ensure water is pushed out of the farthest lines first, rather than back into already cleared zones. The key to a successful blowout is using the correct air pressure: too low, and water will remain trapped in the system; too high, and you risk bursting pipes or damaging sprinkler heads and valves. For most residential systems, 50 to 60 PSI is ideal for PVC pipes, while 40 to 50 PSI is recommended for more flexible polyethylene pipes. Never exceed 80 PSI for any sprinkler system, as this can cause permanent damage. The blowout method is the most reliable winterization option for cold climates, as it removes water from every part of the system, unlike manual or automatic drain methods that only clear water from low points or rely on functioning valves that can fail over time. For homeowners asking “How Blow out Sprinkler System?” the blowout method is the most effective, low-risk option when performed correctly.

Tools and Equipment You’ll Need

Before you begin the blowout process, gather the following tools and equipment to ensure the job goes smoothly and safely:

• Portable air compressor: A compressor with a 10-gallon or larger tank is recommended, as small compressors cannot maintain consistent pressure for the duration of the blowout. Look for a model with an adjustable pressure regulator, so you can set the correct PSI for your system. You can rent a suitable compressor from most hardware stores or equipment rental shops for $30 to $70 per day.
• Blowout adapter: This threaded adapter connects your air hose to the blowout port on your sprinkler system’s backflow preventer. Most residential systems use a 3/4-inch or 1-inch hose thread adapter, so check your system’s port size before purchasing or renting one.
• Air hose: A 25 to 50-foot hose will give you enough reach to move around your yard while blowing out each zone. Make sure the hose is in good condition, with no leaks or cracks.
• Pressure gauge (optional but recommended): An inline pressure gauge lets you monitor the PSI going into your system, so you can avoid exceeding the recommended pressure limits.
• Sprinkler head key or screwdriver: If you have stubborn sprinkler heads that won’t sputter air during the blowout, you can use a key to remove the head briefly to let trapped water escape.
• Work gloves and safety glasses: Compressed air can blow debris out of sprinkler heads, so wearing protective gear will prevent injury.
• Bucket and towels: Use these to clean up any residual water that drains from the system during the process.

Never use a leaf blower, shop vac, or low-power compressor for this task, as they do not produce enough consistent pressure to remove all water from the system. Gas-powered compressors are acceptable as long as they have an adjustable pressure regulator and you do not exceed the recommended PSI limits.

Step-by-Step Guide to Blowing Out Your Sprinkler System

Follow these steps carefully to blow out your sprinkler system safely and effectively, minimizing the risk of damage to your pipes and equipment.

Pre-Blowout Preparation

1. Shut off the main water supply to your sprinkler system. Locate the main shutoff valve, which is usually near your home’s water meter or attached to the backflow preventer assembly, and turn it clockwise to stop water flow to the system.
2. Relieve excess pressure and drain initial water from the system by turning on one zone manually via your sprinkler controller. Let the zone run until water stops flowing from the sprinkler heads, then turn the zone off.
3. Turn off power to your sprinkler controller by unplugging it or flipping the dedicated circuit breaker. This prevents the controller from turning on zones unexpectedly while you are working on the system.
4. Inspect your entire sprinkler system for leaks, broken sprinkler heads, or damaged pipes. Repair any issues before proceeding, as blowing out a damaged system can worsen existing problems and leave water trapped in broken sections.
5. Locate the blowout port on your backflow preventer assembly. It is a threaded port, usually covered by a plastic cap, located on the side or top of the backflow preventer. Remove the cap and set it aside.

Connect the Air Compressor

1. Attach the blowout adapter to the blowout port on your backflow preventer, hand-tightening it to avoid damaging the threads.
2. Connect the air hose from your compressor to the blowout adapter, ensuring all connections are tight to prevent air leaks that will reduce pressure during the blowout.
3. Set the compressor’s pressure regulator to 50-60 PSI if your system uses PVC pipes, or 40-50 PSI if it uses polyethylene pipes. Never set the pressure above 80 PSI, regardless of pipe type.
4. Turn on the compressor and let it build to full pressure before starting the blowout process. This ensures consistent air flow as you work through each zone.

Blow Out Each Zone

1. Start with the sprinkler zone that is farthest from the backflow preventer and compressor. Working from farthest to closest prevents you from pushing water back into zones you have already cleared.
2. Open the selected zone valve via your sprinkler controller. This allows air to flow into that zone’s pipes.
3. Hold the compressor trigger open to let air flow into the zone. Watch the sprinkler heads in the zone: they will sputter and shoot water initially, then sputter air, and eventually only release air. Keep the air flowing for at least 30 seconds after the last head stops sputtering to ensure all residual water is removed from the lines.
4. Close the zone valve once the blowout for that zone is complete. Do not leave the zone valve open while the compressor is running, as this can damage the valve’s internal seals.
5. Move to the next farthest zone, repeat the process, and continue until all zones have been blown out. Keep a checklist of your zones to ensure you do not skip any.

Final Shutoff and Cleanup

1. Once all zones are blown out, turn off the compressor and release all pressure from the air hose by pressing the trigger.
2. Close the blowout port cap tightly, then remove the blowout adapter and air hose from the backflow preventer.
3. If your system has a drain valve at the lowest point of the pipe runs, open it to drain any residual water that settled in the pipes during the blowout process. Leave the drain open until no more water flows out.
4. Double-check that the main water supply shutoff valve is fully closed for the winter, to prevent water from flowing back into the system if there is a leak in your home’s plumbing.
5. Store your compressor, adapter, and other tools in a dry, protected area for next year’s use.

Blowout Method vs. Alternative Winterization Methods

While the blowout method is the most effective option for cold climates, there are other winterization methods you may consider depending on your local climate and system setup. The table below compares the most common options to help you choose the right method for your home:

For most homeowners in cold climates, the blowout method is the only reliable way to prevent freeze damage, even if you have automatic drain valves installed. A blowout adds an extra layer of protection, ensuring no water is left trapped in your system to cause damage during unexpected cold snaps.

Tips and Best Practices for a Successful Blowout

Follow these tips to ensure your sprinkler system blowout goes smoothly and your system is fully protected from winter freeze damage:

• Use a compressor with a 10-gallon or larger tank to maintain consistent pressure. Small compressors often lose pressure mid-blowout, leaving water trapped in pipes.
• Always use a pressure gauge to monitor PSI, even if your compressor has a built-in regulator. Regulators can drift, leading to excessive pressure that damages pipes.
• Blow out the farthest zone from the backflow preventer first, then work your way closer to the house. This pushes water out of the longest pipe runs first, rather than forcing it back into cleared zones.
• Keep air flowing through each zone for at least 30 seconds after the last sprinkler head stops sputtering. This clears residual water from pipes and heads that may not be visible.
• If you have low or clogged sprinkler heads that do not sputter air during the blowout, remove the head briefly to let trapped water escape, then reattach it once the zone is clear.
• Keep a checklist of all zones to ensure you do not skip any during the process.
• If you are unsure about any step, hire a professional winterization service. The cost is far less than repairing freeze damage.

Common Mistakes to Avoid

Even experienced homeowners can make mistakes during a sprinkler system blowout that lead to system damage. Avoid these common errors to ensure a successful winterization:

1. Using excessive air pressure: This is the most common cause of blowout-related damage. PSI above 80 can burst PVC pipes, break sprinkler heads, and blow out valve seals. Always adhere to the recommended PSI limits for your pipe type, and use a pressure gauge to monitor output.
2. Skipping zones during the blowout: Forgetting to blow out even one zone leaves trapped water that can freeze and crack that section of pipe. Keep a checklist of all your zones and mark each one off as you complete it.
3. Leaving the main water supply on: If the main shutoff valve is open, water can flow back into the system while you are blowing it out, leaving excess water trapped in the pipes. Double-check that the main valve is fully closed before starting the compressor.
4. Using an underpowered compressor: Small compressors with small tanks cannot maintain consistent pressure for the duration of the blowout, especially for larger systems with long pipe runs. Rent a 10-gallon or larger compressor to ensure you have enough power to clear all zones.
5. Not draining low-point drain valves: Even after a thorough blowout, water can settle in the lowest point of your system’s pipes, where it can freeze and crack the pipe. Open any drain valves at low points after the blowout is complete to remove this residual water.
6. Forgetting to turn off the sprinkler controller: If the controller is powered on, it may turn on a zone unexpectedly while you are blowing out another zone, causing damage to valves or pipes. Always unplug the controller or turn off its power before starting the process.

Frequently Asked Questions

How much does it cost to blow out a sprinkler system?

If you perform the blowout yourself, the only cost is renting an air compressor, which typically costs $30 to $70 per day at most hardware stores or equipment rental shops. If you hire a professional, the cost ranges from $100 to $250, depending on system size and location. For most homeowners with standard 4-6 zone systems, DIY blowout is cost-effective if you follow safety steps.

Can I blow out my sprinkler system with a leaf blower?

No, leaf blowers are not suitable for blowing out sprinkler systems. Most leaf blowers produce less than 10 PSI of air pressure, while sprinkler systems require 40-60 PSI to effectively push water out of all pipes, risers, and sprinkler heads. Using a leaf blower will leave significant amounts of water trapped in your system, which can still freeze and cause damage over the winter.

How long does a sprinkler system blowout take?

For a typical residential 4-6 zone system, a DIY blowout takes 45 minutes to 1.5 hours, including setup, blowing out each zone, and cleanup. Professional services usually complete the job in 30 minutes to 1 hour, as they have larger, more efficient compressors and experience with the process. Exact time varies based on system size and number of zones.

What happens if I don’t blow out my sprinkler system?

If you skip the blowout process, any water left in your sprinkler system will freeze when temperatures drop below 32°F (0°C). As water freezes, it expands, which can crack pipes, burst sprinkler heads, and damage zone valves. When you turn the system back on in the spring, these damaged components will leak, leading to water waste, lawn damage, and repair costs ranging from $200 for a single broken head to $2,000 or more for full pipe replacement. In severe cases, a burst pipe can also cause water damage to your home’s foundation or basement if the pipe is located near the structure.

Can I blow out my sprinkler system myself?

Yes, most homeowners can safely blow out their own sprinkler system if they follow the steps outlined in this guide, use the correct equipment, and adhere to recommended PSI limits. However, if you have a large commercial system, are uncomfortable operating an air compressor, or notice existing damage to your pipes or heads, it is best to hire a professional. A professional blowout is a small cost compared to the expense of repairing freeze damage caused by improper DIY work.

Conclusion

Blowing out your sprinkler system is a critical annual maintenance task for homeowners in cold climates, and the blowout method is the most effective way to eliminate the risk of freeze-related damage. By following the step-by-step guide outlined above, using the right tools, and avoiding common mistakes, you can protect your sprinkler system from costly repairs and ensure it works perfectly when you restart it in the spring. You now have a clear, practical answer to “How Blow out Sprinkler System?” that will keep your lawn and landscaping healthy year after year. If you ever feel unsure about any part of the process, don’t hesitate to hire a professional winterization service – the small upfront cost is well worth the peace of mind and protection of your investment.