How to Blow down Sprinkler System? Remove Water & Air

Introduction

If you live in a region with freezing winters, you know that your sprinkler system needs special attention before the first frost hits. One of the most effective methods for protecting underground irrigation pipes, sprinkler heads, and valves from freezing damage is to completely drain the water from the system. This process, commonly referred to as “blowing down” the sprinkler system, uses compressed air to push out residual water that gravity drainage alone cannot remove.

Learning how to blow down a sprinkler system properly is essential for homeowners who want to avoid costly repairs caused by frozen pipes bursting or sprinkler components failing due to ice expansion. When water freezes inside a pipe or sprinkler head, it expands. That expansion creates pressure that can crack PVC pipes, break sprinkler heads, destroy valve diaphragms, and damage backflow preventers. These repairs can cost hundreds or even thousands of dollars, making the relatively simple process of blowing down your system a smart investment every fall.

This guide will walk you through everything you need to know about blowing down your sprinkler system safely and effectively. You will learn when to perform the procedure, what tools and equipment you need, how to prepare your system, step-by-step instructions for the blow down process, and important safety considerations to keep in mind. Whether you are a first-time homeowner tackling winterization for the first time or an experienced DIYer looking to refine your technique, this article will provide the knowledge you need to protect your irrigation system from winter damage.

Table of Contents

• Understanding Sprinkler System Winterization
• Why a Blow Down Is Critical for Freeze Protection
• Tools and Equipment You Will Need
• When to Blow Down Your Sprinkler System
• Preparation Steps Before You Begin
• Step-by-Step Guide to Blowing Down Your System
• Different Blow Down Techniques Explained
• Troubleshooting Common Issues During Blow Down
• Blow Down vs. Other Winterization Methods
• Tips and Best Practices
• Common Mistakes to Avoid
• Safety Considerations
• Maintenance After Blow Down
• Frequently Asked Questions
• Conclusion

Understanding Sprinkler System Winterization

Sprinkler system winterization is the process of removing water from your irrigation system before freezing temperatures arrive. This is necessary because water expands when it freezes, and that expansion can cause significant damage to every component of your sprinkler system. The winterization process typically involves three main steps: shutting off the water supply, draining the system, and blowing out any remaining water using compressed air.

There are two primary methods for draining a sprinkler system. The first is gravity drainage, which relies on opening drain valves and the highest sprinkler heads to allow water to flow out naturally. While this method removes a substantial amount of water, it does not remove all of it. Water trapped in low spots, behind valves, or in sprinkler riser pipes often remains. The second method is the blow down, which uses compressed air to force out that residual water that gravity drainage missed.

The blow down method is particularly important for systems that have automatic drain valves or for homeowners who live in areas with extremely cold winters where even small amounts of trapped water can cause damage. By combining gravity drainage with a thorough blow down, you maximize your chances of preventing freeze-related damage to your entire irrigation system.

Why a Blow Down Is Critical for Freeze Protection

Even after you have shut off the main water supply and opened all the drain valves, water will still remain in your sprinkler system. This residual water collects in several areas: the bottom of vertical riser pipes that feed sprinkler heads, the chambers inside control valves, the low points of main lines, and the internal passages of backflow preventers. These pockets of water are exactly where ice forms first and where damage occurs most frequently.

A blow down addresses these problem areas by introducing compressed air into the system at a controlled pressure. The air travels through the pipes and pushes the remaining water out through the sprinkler heads, drain valves, and any open ports. This process is especially critical for pop-up sprinkler heads, which have internal riser mechanisms that hold water even after the system has been drained. Without a blow down, these components are vulnerable to cracking when temperatures drop below freezing.

In regions where winter temperatures regularly fall well below 32 degrees Fahrenheit, a proper blow down can mean the difference between a system that survives the winter intact and one that requires extensive and expensive repairs in the spring. The investment in time and equipment for a blow down is minimal compared to the cost of replacing damaged pipes, valves, and sprinkler heads.

Tools and Equipment You Will Need

Blowing down your sprinkler system requires specific tools and equipment. Having everything ready before you start will make the process smoother and safer. Here is a comprehensive list of what you will need:

• Compressed air source: A portable air compressor with at least 20 CFM (cubic feet per minute) at 90 PSI is recommended for most residential systems. Larger systems may require higher capacity.
• Air compressor fittings: Various couplers, adapters, and fittings to connect the air compressor hose to your system’s backflow preventer or blow down valve.
• Pressure gauge: To monitor the air pressure entering the system and prevent over-pressurization.
• Shut-off valve: To control the flow of compressed air into the system.
• Safety glasses and hearing protection: Compressed air can propel debris and is extremely loud.
• Work gloves: For handling fittings and protecting your hands.
• Towels and rags: For cleaning up any water or condensation.
• Drain wrench or appropriate tools: To open and close drain valves and fittings.

If you do not own an air compressor, many hardware stores and tool rental centers rent them out seasonally. Some irrigation professionals also offer blow down services, which may be worth considering if your system is large or complex.

When to Blow Down Your Sprinkler System

Timing is crucial when it comes to blowing down your sprinkler system. You should perform the blow down after the growing season has ended but before the first hard freeze of the year. In most regions, this window falls between late September and early November, depending on your local climate zone.

A general rule of thumb is to wait until daytime temperatures consistently stay below 50 degrees Fahrenheit but before nighttime temperatures drop below 28 degrees Fahrenheit. This timing ensures that you are not prematurely shutting down a system that still needs to water your lawn, while also giving you enough time to complete the process before freezing conditions arrive unexpectedly.

If you live in an area with unpredictable weather patterns, it is better to err on the side of caution and blow down your system earlier rather than risk being caught off guard by an early freeze. An early blow down will not harm your system, but a late one could result in expensive damage that could have been easily prevented.

Preparation Steps Before You Begin

Before you connect the air compressor and begin the blow down process, there are several important preparation steps that must be completed. These steps ensure that the process is efficient, safe, and effective.

Step 1: Shut Off the Water Supply

Locate your main irrigation shut-off valve, which is typically near the water meter or where the irrigation line branches off from your home’s main water supply. Turn this valve clockwise to shut off the water completely. If your system has a dedicated irrigation shut-off valve, use that. If not, you may need to shut off the main water supply to your house.

Step 2: Perform Gravity Drainage

Open all drain valves on your system. These are usually located at the lowest points of the main lines and at the backflow preventer assembly. Also, open the highest sprinkler heads on each zone. This allows most of the water to drain out naturally through gravity before you apply compressed air.

Step 3: Activate the Controller

Set your irrigation controller to the “off” position or remove the power source. This prevents the system from accidentally activating during the blow down process, which could be dangerous if water or air is suddenly released.

Step 4: Check and Open All Valves

Manually open each zone valve using the manual bleed screw or the solenoid. This ensures that air can flow through every zone and reach all the sprinkler heads. If any zone valve remains closed, the air pressure will build up without effectively clearing water from that section.

Step-by-Step Guide to Blowing Down Your System

Now that your system is prepared, you can begin the actual blow down process. Follow these steps carefully to ensure thorough and safe removal of all water from your sprinkler system.

Step 1: Connect the Air Compressor

Attach the air compressor hose to the blow down fitting on your backflow preventer or the dedicated blow down port on your system. Most residential systems have a threaded connection or quick-connect fitting specifically for this purpose. If your system does not have a dedicated blow down port, you can often connect to the test port on the backflow preventer using an appropriate adapter. (See Also:Where Is Sprinkler Valve Located)

Ensure all connections are secure and airtight. A loose connection will reduce the effectiveness of the blow down and could create a safety hazard from the high-pressure air.

Step 2: Set the Air Pressure

Set your air compressor to deliver between 40 and 80 PSI. The exact pressure depends on your system type and size. PVC pipes and plastic fittings can be damaged by excessive pressure, so it is important not to exceed the recommended limits. If you are unsure of your system’s pressure tolerance, start at a lower pressure and gradually increase it.

Use the pressure gauge to monitor the incoming air pressure. Never exceed 100 PSI regardless of your system type, as this can cause fittings to fail or pipes to burst.

Step 3: Blow Down the First Zone

Start with the zone that is closest to the air compressor connection. Open the manual bleed screw on the zone valve fully. Turn on the air compressor and allow air to flow into the system. You will see water and mist coming out of the sprinkler heads as the air pushes the remaining water out.

Continue blowing air through the zone until only air comes out of all the sprinkler heads. This typically takes 30 seconds to two minutes per zone, depending on the size of the zone and the amount of residual water. When you see a steady stream of dry air with no water mist, that zone is complete.

Step 4: Proceed to Remaining Zones

After completing the first zone, turn off the air compressor and close that zone’s manual bleed screw. Move to the next zone, open its manual bleed screw, and repeat the process. Work through each zone systematically until all zones have been blown down.

If you have a system with many zones, you may need to allow the air compressor to rest between zones to prevent it from overheating. Most small portable compressors are not designed for continuous operation at high duty cycles.

Step 5: Perform a Final Check

Once all zones have been blown down, turn off the air compressor and disconnect the hose. Open all drain valves one more time to allow any remaining condensation to escape. Close all drain valves and sprinkler heads once you are confident that no water remains in the system.

For added protection, you can perform a second blow down pass on any zones that showed signs of water during the first pass.

Different Blow Down Techniques Explained

There are several approaches to blowing down a sprinkler system, and the best technique depends on your system configuration, available equipment, and local conditions. Understanding these different methods will help you choose the most effective approach for your situation.

Sequential Zone Blow Down

This is the most common and recommended technique. You work through each zone one at a time, fully clearing water from each section before moving on to the next. This method ensures that no zone is missed and allows you to verify that each zone is completely dry.

Simultaneous Zone Blow Down

In this method, you open multiple zone valves at the same time and blow air through all zones simultaneously. This can be faster for systems with many zones, but it requires a high-capacity air compressor and can be less thorough since you cannot easily verify that each zone is completely dry.

Pressure Pulse Method

This technique involves short bursts of compressed air rather than a continuous stream. The pulses can be effective at dislodging water that has settled in low spots, but it requires careful monitoring to avoid over-pressurizing the system.

Reverse Flow Blow Down

In this method, you introduce compressed air at the end of the line farthest from the water source and push water toward the supply side. This can be useful for systems with unusual layouts but is more complex to set up and not commonly used by homeowners.

Troubleshooting Common Issues During Blow Down

Even with careful preparation, you may encounter issues during the blow down process. Here are some common problems and how to resolve them:

No Water Coming Out of Sprinkler Heads

If you see no water or mist coming out of the sprinkler heads when you start the blow down, the zone valve may not be fully open. Double-check that the manual bleed screw is completely loosened. Also, verify that the zone valve is actually opening and not stuck closed.

Low Air Pressure

If the air pressure seems weak or insufficient, check for air leaks in your connections. Tighten any loose fittings and ensure all couplers are properly seated. Your air compressor may also be undersized for your system. In that case, consider renting a higher-capacity unit or contacting a professional.

Water Still Present After Blow Down

If water continues to come out of sprinkler heads after several minutes of blowing, there may be a low spot in the piping that is holding water. Try increasing the pressure slightly or moving the air connection to a different point in the system. Sometimes, physically raising the sprinkler head or drain valve can help release trapped water.

Sprinkler Head Damage from Air Pressure

If you notice that sprinkler heads are being damaged or ejected from the ground during the blow down, the air pressure is likely too high. Reduce the pressure immediately and check that all sprinkler heads are properly seated in the ground. Some older or damaged sprinkler heads may need to be replaced before the blow down can be completed safely.

Blow Down vs. Other Winterization Methods

The following table compares the blow down method with other common approaches to sprinkler system winterization, helping you understand the advantages and disadvantages of each: (See Also:How To Troubleshoot A Sprinkler Valve)

Tips and Best Practices

Here are some valuable tips and best practices to help you achieve the most effective blow down of your sprinkler system:

• Start early: Do not wait until the last minute. If you encounter problems, you will have time to address them before freezing temperatures arrive.
• Know your system: Before you begin, walk through your yard and identify all sprinkler heads, zone valves, and drain valves. Take photos if needed for reference.
• Use the right pressure: Never exceed 80 PSI for residential systems with PVC components. Higher pressure can cause fittings to fail.
• Monitor the air flow: Watch the sprinkler heads and listen for changes in sound. When water stops coming out and you hear only air hissing, the zone is likely clear.
• Keep the compressor running: Do not turn off the air compressor between zones if you can avoid it. Keeping it running maintains consistent pressure and reduces the risk of water settling back into pipes.
• Document your work: Keep a record of which zones you have blown down and when. This information is useful for future reference and for tracking any recurring issues.
• Check the weather forecast: Plan your blow down on a dry day when temperatures are above freezing. Working in wet or freezing conditions makes the process more difficult and less effective.
• Have a helper: Ask someone to help you monitor the sprinkler heads while you manage the air compressor. It is difficult to watch all zones simultaneously on your own.

Common Mistakes to Avoid

Even experienced homeowners can make mistakes when blowing down their sprinkler systems. Here are some of the most common errors and how to avoid them:

Mistake 1: Using Excessive Air Pressure

One of the most dangerous mistakes is applying too much compressed air pressure. Pressures above 100 PSI can rupture PVC pipes, blow off fittings, and launch sprinkler heads out of the ground at dangerous speeds. Always stay within the recommended pressure range of 40 to 80 PSI for residential systems and monitor your gauge constantly.

Mistake 2: Skipping Gravity Drainage

Some homeowners skip the gravity drainage step and go straight to the blow down. This is a mistake because gravity drainage removes the bulk of the water, making the blow down faster and more effective. Without this initial step, you will need to run the air compressor for much longer, increasing the risk of overheating and reducing overall efficiency.

Mistake 3: Not Checking All Zones

It is easy to forget about a zone, especially on larger properties. Every zone must be blown down individually. Create a checklist and mark off each zone as you complete it to ensure nothing is missed.

Mistake 4: Connecting to the Wrong Point

Connecting the air compressor to the wrong part of the system, such as the water supply side instead of the discharge side, will not effectively clear the system. Always connect to the blow down port or the discharge side of the backflow preventer.

Mistake 5: Rushing the Process

Rushing through the blow down or not spending enough time on each zone can leave water behind. Take your time and ensure that each zone produces only dry air before moving on to the next one.

Safety Considerations

Blowing down a sprinkler system involves high-pressure air, which presents several safety risks. Following proper safety protocols is essential to prevent injury:

• Always wear eye protection: Flying debris, water, and ice particles can be ejected from sprinkler heads at high velocity. Safety glasses or goggles are essential.
• Wear hearing protection: Compressed air released through sprinkler heads and valves is extremely loud and can cause hearing damage with prolonged exposure.
• Never aim air at people or animals: High-pressure air can cause serious injury. Keep all people and pets away from sprinkler heads during the blow down process.
• Check for underground utilities: Before digging or disturbing soil around sprinkler heads and valves, call 811 to have underground utilities marked.
• Secure the air compressor: Make sure the compressor is on stable, level ground and cannot tip over during operation.
• Monitor equipment: Never leave the air compressor unattended while it is running. Check for overheating, oil leaks, and unusual noises.
• Use proper lifting techniques: Air compressors can be heavy. Use proper lifting form or get help to avoid back injuries.

Maintenance After Blow Down

After completing the blow down, there are several maintenance tasks you should perform to ensure your system remains protected throughout the winter and is ready for spring startup:

Inspect Components for Damage

Walk through your yard and inspect all visible sprinkler heads, pipes, and fittings for any signs of damage. Look for cracked or broken sprinkler heads, loose fittings, or damaged risers. Replace any damaged components before the spring startup to avoid issues later.

Cover the Backflow Preventer

The backflow preventer assembly is particularly vulnerable to freezing. If it is not already insulated, install a foam or insulated cover over it. Some homeowners also wrap the assembly in heat tape, although this should be done according to manufacturer instructions and local electrical codes.

Protect the Main Shut-Off Valve

If your main irrigation shut-off valve is above ground, insulate it with foam pipe insulation or a small enclosure. Even buried valves can be at risk if they are in areas where frost penetrates deeply.

Plan for Spring Startup

Mark your calendar for the spring startup date. Typically, you can reactivate your system in early spring after the danger of frost has passed. Having a plan in place will help you remember important steps and avoid delays when the growing season begins.

Frequently Asked Questions

How long does it take to blow down a sprinkler system?

The time required to blow down a sprinkler system depends on the size of the system, the number of zones, and the capacity of your air compressor. A typical residential system with 4 to 8 zones can usually be completed in 30 to 60 minutes. Larger systems with more zones may take longer, especially if you need to allow the compressor to cool down between zones. (See Also:How To Splice Sprinkler Pipe)

What PSI should I use to blow down my sprinkler system?

For most residential sprinkler systems, the recommended air pressure range is between 40 and 80 PSI. Never exceed 100 PSI, as this can damage PVC pipes and fittings. Start at a lower pressure and gradually increase it if needed. The exact pressure may vary depending on your system’s specifications, so consult your system’s manual if available.

What size air compressor do I need?

You need an air compressor that can deliver at least 20 CFM (cubic feet per minute) at 90 PSI for most residential systems. Larger systems or those with many zones may require a compressor with higher capacity. If you do not own a suitable compressor, many hardware stores and tool rental centers offer them for rent, especially during the fall and spring seasons.

Can I blow down my sprinkler system more than once?

Yes, you can perform a second blow down pass on any zones that showed signs of water during the first pass. This is particularly useful for systems with low spots or unusual layouts where water tends to collect. However, a single thorough blow down should be sufficient for most residential systems if done correctly.

Is it worth hiring a professional to blow down my sprinkler system?

For simple residential systems, a DIY blow down is usually sufficient and cost-effective. However, if you have a large or complex system, or if you are uncomfortable working with compressed air equipment, hiring a professional may be worth the investment. Professional services typically cost between $100 and $300, depending on your location and system size.

What if water still comes out after blowing down?

If water continues to come out of sprinkler heads after several minutes of blowing, there may be a low spot in the piping holding water. Try increasing the pressure slightly or moving the air connection to a different point in the system. Sometimes, physically raising the sprinkler head or drain valve can help release trapped water. If the problem persists, you may need to investigate for blockages or damaged pipes.

Do I need to remove the backflow preventer for winterization?

In most cases, you do not need to remove the backflow preventer entirely. However, you should drain it thoroughly and insulate it for protection. Some homeowners choose to remove above-ground backflow assemblies for indoor storage during the winter, which provides the best protection. If your backflow preventer is buried or difficult to access, proper insulation and thorough draining are the best alternatives.

What temperature triggers the need for a blow down?

You should perform a blow down when daytime temperatures consistently stay below 50 degrees Fahrenheit and nighttime temperatures approach or drop below 32 degrees Fahrenheit. The exact timing varies by location, but the key is to complete the process before the first hard freeze. In marginal climates, it is better to blow down earlier rather than risk damage from an unexpected freeze.

Conclusion

Learning how to blow down a sprinkler system is an essential skill for any homeowner in a climate where freezing temperatures are a concern. By combining gravity drainage with a thorough compressed air blow down, you can effectively remove nearly all water from your irrigation system and protect it from freeze-related damage throughout the winter months.

The process requires the right equipment, proper timing, and attention to safety, but it is well within the capabilities of most homeowners. Taking the time to perform a complete blow down each fall will save you from the stress and expense of dealing with burst pipes, damaged valves, and broken sprinkler heads when spring arrives. Remember to start early, use appropriate air pressure, work through each zone systematically, and always prioritize safety when working with compressed air.

With the knowledge and guidance provided in this article, you now have everything you need to successfully blow down your sprinkler system and protect your investment in your home’s irrigation infrastructure. Whether you choose to do it yourself or hire a professional, the key is to ensure that your system is properly winterized before freezing temperatures arrive.