How to Drain Rainbird Sprinkler System? Auto Drain Valves

Introduction

Winter is on its way, and if you own a Rain Bird sprinkler system, you are probably already thinking about how to protect it from costly freeze damage. Rain Bird is one of the most popular residential irrigation brands on the market, known for its durable, reliable systems, but even the best sprinkler systems can be destroyed by freezing temperatures if water is left trapped in the pipes. Auto drain valves are a game-changing feature that makes draining your system far easier than traditional manual methods, but many homeowners don’t know how to use them properly, or skip key steps that leave water trapped in the system. This comprehensive guide will walk you through exactly how to drain Rainbird sprinkler system, including how auto drain valves work, a full step-by-step draining process, winterization tips, common mistakes to avoid, and answers to frequently asked questions. Whether you are a new homeowner installing your first Rain Bird system or a long-time user looking to refresh your maintenance routine, this guide has everything you need to protect your investment and avoid expensive repairs in the spring.

• Why Draining Your Rain Bird Sprinkler System Is Critical
• How Rain Bird Auto Drain Valves Work
• Tools and Materials You’ll Need
• Step-by-Step Guide to Draining a Rain Bird Sprinkler System with Auto Drain Valves
• Manual Draining Alternative for Systems Without Auto Drain Valves
• Fall Winterization Tips to Extend Your System’s Lifespan
• Common Draining Mistakes to Avoid
• Post-Drain Maintenance for Spring Start-Up
• Frequently Asked Questions
• Conclusion

Why Draining Your Rain Bird Sprinkler System Is Critical

Water expands by 9% when it freezes, so even a small amount of water left in a pipe can generate enough pressure to crack PVC or copper pipes, break sprinkler heads, or rupture valve diaphragms. A single cracked pipe can lead to thousands of dollars in repairs, not to mention the cost of re-sodding lawn areas damaged by leaks. Rain Bird systems are built to last 15-20 years with proper maintenance, but skipping the annual draining process can cut that lifespan in half. Even in mild climates, a sudden cold snap with temperatures dropping below freezing for several hours can cause damage if water is left in the lines. Auto drain valves are designed to mitigate this risk, but they only work if installed correctly and paired with proper draining techniques to ensure all water is removed from the system.

How Rain Bird Auto Drain Valves Work

Rain Bird auto drain valves are passive, electricity-free devices that require no manual adjustment to operate. They are installed at the lowest point of each lateral line (the pipes that run between sprinkler heads) and any low spots in the main supply line. Inside the valve is a spring-loaded diaphragm that keeps the valve closed when water pressure in the line is above 10-15 PSI, the normal operating pressure for most residential sprinkler systems. When you turn off the main water supply and run stations to relieve pressure, line pressure drops below the activation threshold, causing the diaphragm to open and allow water to drain out through the valve’s outlet. Once water has drained and pressure hits zero, the spring closes the valve to keep debris out of the line. When you turn water back on in spring, pressure builds and pushes the diaphragm closed, sealing the valve for normal operation.

Rain Bird sells 1/2″ models for lateral lines and 3/4″ models for main lines, compatible with all standard Rain Bird systems and easy to install on existing setups. To help you choose the right drainage method for your needs, refer to the comparison table below:

Tools and Materials You’ll Need

Gathering the right tools before you start will make the draining process faster and more efficient. You will need the following supplies:

• Adjustable wrench: For turning the main water shut-off valve and removing auto drain valve caps if needed.
• Flathead and Phillips screwdrivers: For removing valve cover screws and adjusting sprinkler heads during spring checks.
• Garden hose: For flushing debris from valves and testing the system in spring.
• Air compressor (10-15 CFM, max 50 PSI): For blowing out remaining water from lines, recommended for cold climates.
• Bucket and rag: For catching draining water and cleaning up spills.
• Work gloves: To protect hands from sharp pipe edges and debris.
• Insulation foam (optional): For covering exposed backflow preventers and pipes to prevent freezing.

Step-by-Step Guide to Draining a Rain Bird Sprinkler System with Auto Drain Valves

If your Rain Bird system is equipped with auto drain valves, follow this process to fully drain the system and protect it from freeze damage.

Pre-Drain Preparation

First, locate the main water supply shut-off valve for your sprinkler system, usually located near the backflow preventer installed between your home’s water supply and the irrigation lines. Turn the shut-off valve clockwise to stop all water flow to the sprinklers. Next, turn on your sprinkler controller and run each station for 1-2 minutes, one at a time, starting with the zone farthest from the main water supply. This will relieve pressure from the lines and push as much water as possible out through the sprinkler heads before the auto drain valves activate. Once you have run all stations, turn off the controller and unplug it from the power source to prevent accidental activation during the draining process. Finally, locate all auto drain valves in your system, installed at the lowest point of each lateral line near the last sprinkler head and at low spots in the main supply line. Most Rain Bird auto drain valves have a small removable cap for cleaning and an outlet pipe that drains water away from the valve.

Activate the Auto Drain Valves

After running all sprinkler stations, wait 10-15 minutes for line pressure to drop below the 10-15 PSI threshold required to open auto drain valves. You will know the valves are activating when you hear a hissing sound from the outlets, followed by water draining onto the ground. If temperatures are below freezing, direct drainage into a bucket or away from walkways to avoid ice buildup. Check each valve individually to confirm it is draining. If a valve is not draining after 15 minutes, it may be clogged with debris. Turn off the main water supply, remove the valve cap, and use a small screwdriver or wire to clear dirt, grass clippings, or small stones from the internal screen. Flush the valve with a garden hose, reattach the cap, and wait 5 more minutes to see if it begins draining. Allow all valves to drain completely, which takes 20-30 minutes for most residential systems, up to an hour for larger properties.

Blow Out Remaining Water (Optional but Recommended for Cold Climates)

Auto drain valves only remove water from low points, so water can still be trapped in high spots in the pipes, the main supply line, or inside sprinkler heads. For areas where temperatures regularly drop below 20°F, we strongly recommend blowing out the lines with an air compressor to remove all remaining water. Connect your air compressor to the sprinkler system’s blow-out port, usually located near the backflow preventer with a threaded cap. Attach the compressor hose using a quick-connect adapter, and set the compressor to no more than 50 PSI to avoid damaging pipes, heads, or valves. Never use more than 50 PSI, as this can cause pipes to burst, sprinkler heads to crack, and valve diaphragms to rupture. If you do not have an air compressor, many hardware stores rent them for $30–$50 per day, or you can hire a professional irrigation technician to perform the blow-out for $100–$200, which is a worthwhile investment for large systems or cold climates.

Start with the zone farthest from the compressor, turn on the zone, and run the compressor for 2-3 minutes until you see a steady stream of air (no water) coming out of the farthest sprinkler head in that zone. Repeat for all remaining zones, then turn off the compressor and reattach the cap to the blow-out port. Wait 10 minutes after blowing out to see if any auto drain valves open to release additional dislodged water.

Post-Drain Verification

Once all draining and blowing out is complete, perform a final check to ensure no water remains in the system. Visually inspect each auto drain valve to confirm no water is dripping or flowing out. Check all sprinkler heads to ensure no water is leaking or pooling around the base of the heads, which can indicate a broken diaphragm or clogged valve. If you have manual drain valves installed in addition to auto drains, close them securely to prevent dirt, debris, and insects from entering the system over the winter. Finally, cover any exposed backflow preventers, above-ground pipes, and valves with insulation foam, which you can purchase at any hardware store for less than $10, to protect them from freezing temperatures. Secure the foam with duct tape or zip ties to keep it in place all winter, even if there is snow or heavy wind.

Manual Draining Alternative for Systems Without Auto Drain Valves

If your Rain Bird system does not have auto drain valves installed, you will need to drain it manually each fall. Manual drain valves are a lower-cost alternative to auto drain valves, but they require you to remember to open them each fall before the first freeze. If you forget to open them, water left in the lines can freeze and cause damage, just like a system with no drain valves at all. First, turn off the main water supply to the system. Locate all manual drain valves, usually installed at the lowest point of each lateral line and main line, and open them fully. Run each sprinkler station for 1-2 minutes to relieve pressure and let water drain out of the lines. Open the main line low point drain if your system has one to drain the supply pipe. Blow out the lines with an air compressor as outlined above to remove remaining water, then close all manual drain valves securely and insulate exposed components.

Fall Winterization Tips to Extend Your System’s Lifespan

Beyond draining your system, these tips will help you avoid common winter damage and extend the lifespan of your Rain Bird irrigation system:

• Drain your system before the first expected freeze, usually late October to early November in most cold climates. If a sudden cold snap is forecast earlier in the fall, drain the system early to avoid damage.
• Mark all auto drain valves with small flags or spray paint so you can easily locate them for spring maintenance, saving you time when checking for clogs or damage.
• Disconnect and store your Rain Bird rain sensor indoors for the winter, as freezing temperatures can damage the sensor’s internal components and lead to inaccurate readings in the spring.
• If you have a connected drip irrigation system, drain it separately before the main sprinkler system, as drip lines hold more water than spray heads and are more prone to freeze damage.
• Avoid using rock salt or other harsh de-icing products near sprinkler heads and exposed pipes, as these can corrode metal components and damage PVC over time. Use sand or pet-safe de-icer instead if you need to melt ice near your irrigation system.
• If you will be away from home for an extended period during the winter, ask a neighbor or friend to check on your system periodically to ensure no pipes have burst or leaked due to freezing.

Common Draining Mistakes to Avoid

Even small errors during the draining process can leave water trapped in your system, leading to costly freeze damage. Avoid these common pitfalls:

1. Forgetting to turn off the main water supply first: This is the most common mistake homeowners make. If you leave the main supply on, water will continue to flow into the lines, refilling them as fast as auto drains can empty them, leaving water trapped in the system that can freeze. Always turn off the main supply before running any stations.
2. Using excessive PSI when blowing out lines: Many people think higher air pressure will remove more water, but this is a dangerous misconception. Sprinkler systems are designed to operate at 40-50 PSI, so using air pressure above 50 PSI can cause pipes to burst, sprinkler heads to crack, and valve diaphragms to rupture. Always use a pressure regulator on your compressor to stay under the 50 PSI limit.
3. Not waiting long enough for auto drain valves to activate: After turning off the water and running the stations, you need to wait at least 10-15 minutes for pressure to drop low enough for auto drain valves to open. If you turn off the water and immediately leave, you may miss water trapped in high spots that can freeze and cause damage.
4. Leaving manual drain valves open all winter: If you have manual drain valves, always close them after draining is complete. Leaving them open allows dirt, debris, leaves, and insects to enter the system, which can cause clogs in the spring and damage to valve components.
5. Skipping the blow-out step in cold climates: Auto drain valves only remove water from low points in the system. Water can still be trapped in high spots in the pipes, the main supply line, and inside sprinkler heads, which can freeze and cause damage even if auto drains are working properly. For areas with sustained temperatures below 20°F, blowing out the lines is a necessary step to ensure all water is removed.

Post-Drain Maintenance for Spring Start-Up

When the weather starts to warm up in the spring, you will need to perform a few simple steps to get your Rain Bird system back up and running. First, inspect all auto drain valves for debris or damage: remove the cap, clean the internal screen with a small brush, and flush the valve with a garden hose. If a valve is damaged or not sealing properly, replace it with a new Rain Bird auto drain valve, which costs between $10 and $25 and is easy to install with basic tools. Next, close any manual drain valves you opened for winter, and remove any insulation foam you placed on exposed pipes and backflow preventers.

Turn on the main water supply slowly to avoid a pressure surge that can damage the system’s valves. Once the water is on, run each sprinkler station for 2-3 minutes to check for leaks, broken heads, or clogged nozzles. Replace any damaged components, and adjust the spray pattern of each head to ensure even coverage of your lawn and garden. If you notice any leaks when you first turn the water back on, turn off the main supply immediately and fix the issue before running the system again, as leaks can lead to water waste and further damage to pipes and valves. Finally, update your sprinkler controller’s schedule for the growing season, adjusting run times and days based on your local climate and plant needs. Test the rain sensor to make sure it is working properly, as it will override the controller’s schedule during rainfall to save water.

Frequently Asked Questions

How often do I need to drain my Rain Bird sprinkler system?

You only need to drain your Rain Bird sprinkler system once per year, before the first expected freeze in the fall. If you live in a climate with mild winters where temperatures rarely drop below 32°F, you may not need to drain the system at all, but it is still recommended as a precaution if a sudden cold snap with below-freezing temperatures is forecast. For areas with harsh winters where temperatures regularly drop below 20°F, draining the system annually is a non-negotiable step to prevent costly freeze damage. If you experience an unexpected cold snap in late fall or early spring, it is a good idea to drain the system temporarily to protect it from damage, even if you already drained it for the season.

Are auto drain valves enough to prevent freeze damage?

In most cases, yes, if they are installed correctly at all low points in your system and you live in an area where temperatures stay above 20°F for most of the winter. Rain Bird auto drain valves are designed to automatically release water from low spots in the lines when pressure drops, which eliminates the need to manually open drain valves each fall. However, for areas with sustained temperatures below 20°F, we recommend combining auto drain valves with a blow-out winterization step to remove all water from high spots in the pipes and the main supply line, as auto drains only remove water from low elevations. Trapped water in high spots can still freeze and cause damage even if auto drains are installed. Auto drain valves are also low-maintenance, requiring only an annual cleaning of the internal screen to keep them working properly.

What PSI should I use when blowing out my Rain Bird sprinkler system?

Never exceed 50 PSI when using an air compressor to blow out your Rain Bird sprinkler system. Most residential Rain Bird systems are designed to operate at 40-50 PSI, so using higher air pressure can cause serious damage, including burst pipes, cracked sprinkler heads, and ruptured valve diaphragms. A compressor with 10-15 CFM (cubic feet per minute) is sufficient for most residential systems, which will blow out water from all zones without exceeding the safe pressure limit. Using a pressure regulator on your compressor is the best way to ensure you do not exceed the 50 PSI limit, even if the compressor’s default setting is higher. If you are unsure about using an air compressor, hire a professional irrigation technician to perform the blow-out for you, as they have the proper equipment and experience to do it safely.

What do I do if my auto drain valve is clogged?

If your auto drain valve is not draining water after the system has been depressurized, it is likely clogged with debris such as dirt, grass clippings, small stones, or leaves. First, turn off the main water supply to the system to prevent water from spraying out when you remove the cap. Use a small screwdriver or piece of wire to clear any debris from the valve’s internal screen, which is located just under the top cap. Flush the valve with a garden hose to remove any remaining debris, then reattach the cap. Turn the water supply back on and run a sprinkler station to build pressure, then turn it off and wait 10 minutes to see if the valve drains properly. If the valve is still clogged or not sealing correctly, replace it with a new Rain Bird auto drain valve, which costs between $10 and $25 and is easy to install with basic tools. If you frequently have clogged auto drain valves, consider installing a small mesh screen over the valve outlet to keep debris out.

Do I need to drain my system in the spring?

No, you do not need to drain your Rain Bird sprinkler system in the spring. Auto drain valves will automatically close when you turn the main water supply back on and build pressure in the lines, so they will not interfere with normal system operation. If you opened manual drain valves for winter, simply close them securely before turning the water supply back on. Once the system is pressurized, run each zone for a few minutes to check for leaks and ensure all sprinkler heads are working properly before setting your controller schedule for the growing season. If you notice water pooling around auto drain valves in the spring, it may be a sign that the valve is not sealing properly, and should be replaced to prevent leaks during the operating season.

Conclusion

Draining your Rain Bird sprinkler system is one of the most important maintenance tasks you can perform to protect your investment and avoid costly repairs. Auto drain valves make this process much simpler than traditional manual draining, as they automatically release water from low points in the lines when pressure drops, eliminating the need to remember to open drain valves each fall. By following the step-by-step guide outlined in this article, using the right tools, avoiding common mistakes, and performing basic post-drain maintenance, you can ensure your system is fully protected from freeze damage all winter long. If you are ever unsure about any part of the draining process, or if you notice persistent leaks or clogs in your auto drain valves, don’t hesitate to contact a professional irrigation technician for assistance. Taking the time to properly drain your system now will save you hundreds or even thousands of dollars in repair costs, and will ensure your lawn and garden get the consistent, reliable water they need when the growing season arrives. Remember, the key to a long-lasting Rain Bird sprinkler system is consistent, seasonal maintenance, and learning how to drain Rainbird sprinkler system properly is the most critical step of all.