How to Drain an Irrigation System: A Complete Guide for…

Winter is coming, and with it, the threat of frozen pipes and damaged irrigation components. If you’re a homeowner or a groundskeeper, you know the importance of protecting your investment. The good news is that with a little preparation and know-how, you can effectively drain your irrigation system, safeguarding it against the harsh winter elements.

This isn’t just about avoiding costly repairs; it’s about ensuring your system is ready to go when spring arrives. Ignoring this crucial step can lead to cracked pipes, blown-out backflow preventers, and a host of other headaches. But don’t worry, we’re here to walk you through the entire process, step by step. Let’s get your system winter-ready!

Why Draining Your Irrigation System Is Crucial

As the temperatures drop, water left standing in your irrigation system can freeze. When water freezes, it expands. This expansion exerts immense pressure on pipes, fittings, valves, and sprinkler heads. This pressure can cause:

• Cracked Pipes: The most common and often most expensive damage.
• Damaged Sprinkler Heads: The internal mechanisms can be compromised, leading to leaks or malfunctions.
• Compromised Valves: Solenoid valves and backflow preventers are particularly vulnerable.
• Leaking Fittings: Joints and connections can split or loosen.

Draining the system removes the water, eliminating the risk of freeze damage. It’s a preventative maintenance task that pays for itself many times over by avoiding costly repairs and ensuring a smooth startup in the spring.

When to Drain Your Irrigation System

The timing for draining your irrigation system is critical. You want to do it before the first hard freeze. This typically means:

• Late Autumn: As soon as your region experiences consistent sub-freezing temperatures or when you’ve finished your last watering cycle for the season.
• Before Extended Cold Snaps: Even if it’s not consistently freezing yet, a severe cold snap can do significant damage.

Don’t wait until the last minute. Allow yourself ample time to complete the process without rushing. It’s also a good idea to check your local weather forecasts regularly.

Methods for Draining an Irrigation System

There are several effective methods for draining an irrigation system. The best method for you will depend on the complexity of your system, your available tools, and your comfort level. We’ll cover the most common and effective techniques:

Method 1: Manual Draining (gravity and Blow-Out)

This is the most common and often the most thorough method, especially for residential systems. It involves a combination of allowing gravity to do its work and using compressed air to expel any remaining water.

Step 1: Shut Off the Water Supply

This is the absolute first step. Locate your main water shut-off valve for the irrigation system. This is usually near your main water meter or where the irrigation system connects to your home’s water supply. Ensure it is completely closed. (See Also: how to size a pump for irrigation)

Step 2: Depressurize the System

With the main valve closed, open a faucet or hose bib connected to the irrigation system (if you have one) to release any residual pressure. Let it run until the water stops flowing.

Step 3: Locate and Open Drain Valves

Most irrigation systems have automatic drain valves or manual drain spigots. These are strategically placed at the lowest points in the system.

• Automatic Drain Valves: These are typically located at the end of main lines and in valve boxes. They are designed to open automatically when the water pressure drops to zero, allowing water to drain out. Ensure they are not clogged with debris.
• Manual Drain Spigots: You might have manually operated valves at low points. Open these to allow water to drain.

If you don’t have dedicated drain valves, you might need to manually drain sections by loosening fittings at low points, but this is less ideal and can be messy.

Step 4: Open All Sprinkler Heads (optional but Recommended)

To ensure all water is expelled from the pipes leading to the sprinklers, you can manually open a few sprinkler heads. This allows air to enter the system as water drains, preventing a vacuum. You can do this by:

• Unscrewing the sprinkler head cap (if applicable) and lifting the riser.
• Using a thin tool to manually lift the riser if it’s not easily accessible.

Be sure to close them again after the draining process is complete or before you introduce air.

Step 5: The Blow-Out Procedure (using Compressed Air)

This is the most critical step for thorough draining and preventing freeze damage. You’ll need an air compressor and an appropriate “blow-out” adapter.

Important Safety Note: Never use more than 50-60 PSI when blowing out your system. Excessive pressure can damage your pipes and components. Always use a regulator on your compressor.

1. Connect the Air Compressor: Attach the blow-out adapter to the connection point where the water supply enters your irrigation system. This is usually at the backflow preventer or the main shut-off valve.
2. Start the Compressor: Begin with a low pressure setting (around 30 PSI) and gradually increase it to your desired level (no more than 50-60 PSI).
3. Open Zones Sequentially: Do NOT blow out the entire system at once. You need to do it zone by zone. Locate your irrigation controller and manually activate each zone one at a time.
4. Monitor Air Flow: As each zone is activated, air will flow through the pipes. You’ll hear the air rushing out of the sprinkler heads. Listen for the sound to change from a sputtering, watery sound to a consistent, dry hiss. This indicates most of the water has been expelled from that zone.
5. Move to the Next Zone: Once a zone is clear, shut off the air and move to the next zone on your controller. Repeat the process for every zone in your system.
6. Final Check: After all zones have been blown out, you can do a final pass with the air compressor at a low pressure to ensure no pockets of water remain.

Tip: Some people prefer to have a helper at the controller to turn zones on and off while another person monitors the air pressure and connection point. (See Also: how much is an irrigation system)

Step 6: Close Drain Valves and Shut Off Air

Once you are confident that all zones have been thoroughly purged of water, close any manual drain spigots you opened. Disconnect the air compressor. Ensure the main water supply valve remains closed.

Method 2: Using a “blow-Out” Adapter and Main Line Drainage

This method is similar to the blow-out procedure but focuses on draining the main lines and then using air to clear the lateral lines.

1. Shut Off Water Supply: As in Method 1, close the main water shut-off valve.
2. Depressurize: Open a faucet to release pressure.
3. Connect Blow-Out Adapter: Connect your air compressor to the appropriate connection point (usually the backflow preventer).
4. Drain Main Lines: If your system has a dedicated drain valve at the lowest point of the main line, open it and allow as much water as possible to drain out by gravity.
5. Blow Out Main Lines: With the main drain valve open, slowly introduce air pressure (under 50-60 PSI). Air will push water out through the main drain. Continue until you hear mostly air. Close the main drain valve.
6. Blow Out Zones: Now, proceed with blowing out each zone individually using the irrigation controller, as described in Step 5 of Method 1.
7. Final Steps: Close all valves and disconnect the compressor.

Method 3: Systems with Built-in “winterization” Features

Some advanced irrigation systems or commercial installations may have specific “winterization” ports or features designed to facilitate draining. Consult your system’s manual if you suspect yours has such capabilities.

These might involve:

• Dedicated winterization valves that allow for easier air connection.
• Automated drain systems that are more robust than standard automatic drain valves.

Always refer to your manufacturer’s instructions for these specialized systems.

Tools and Equipment You’ll Need

Gathering the right tools before you start will make the process smoother and more efficient. Here’s a checklist:

Troubleshooting Common Issues

Even with careful planning, you might encounter a few snags. Here’s how to handle them:

• No Water Draining from Drain Valves: Check for clogs. Debris can accumulate in drain valves. You might need to remove and clean them. Ensure the valves are indeed at the lowest points.
• Air Compressor Not Building Pressure: Check for leaks at the adapter connection or any other fittings. Ensure the compressor is functioning correctly.
• Sprinkler Heads Not Working After Blow-Out: This could indicate a damaged sprinkler head from the process, or a clog in a lateral line that wasn’t fully cleared. Re-run the blow-out for that zone, or manually inspect the sprinkler head.
• System Still Freezing: If you suspect water is still present and your area experienced an unexpected freeze, you may need to excavate and repair damaged sections. This highlights the importance of a thorough blow-out.
• Unsure About Valve Locations: Refer to your irrigation system’s design plans or consult a professional. Incorrectly draining can be worse than not draining at all.

Protecting Other Irrigation Components

While draining the pipes is paramount, don’t forget about other vulnerable parts of your system: (See Also: how much does farm irrigation system cost)

• Backflow Preventer: These devices are expensive and very susceptible to freeze damage. Many have a drain port. Ensure it’s drained thoroughly. Some installers recommend removing them for the winter, but this requires re-testing in the spring.
• Valves: Ensure all water is expelled from valve boxes. If you have older, non-freeze-resistant valves, consider insulating the valve boxes or taking extra care to drain them.
• Pump (if applicable): If your system uses a pump, ensure it’s also drained and protected from freezing. Consult the pump manufacturer’s instructions.
• Filters: Remove and clean any filters. Store them indoors if possible.

When to Call a Professional

While draining an irrigation system is a manageable DIY task for many, there are situations where calling a professional is the wiser choice:

• Complex Systems: Large commercial landscapes or intricate residential designs can be challenging to drain correctly.
• Lack of Tools or Confidence: If you don’t have an air compressor or feel uncomfortable working with compressed air and plumbing, it’s best to hire an expert.
• Previous Damage: If you’ve had freeze damage in the past, a professional can assess the condition of your system and perform a more thorough winterization.
• Time Constraints: If you’re short on time and want the job done right, a professional service can save you stress.

Professionals have specialized equipment and the experience to ensure your system is winterized effectively, giving you peace of mind throughout the colder months.

Spring Start-Up After Winterization

Once spring arrives and the threat of frost has passed, you’ll need to get your system back online. Here’s a quick overview of the start-up process:

1. Inspect the System: Walk through your yard and look for any visible signs of damage to pipes, sprinkler heads, or valves that may have occurred over the winter.
2. Close Drain Valves: Ensure all manual drain valves are closed.
3. Turn on Water Supply Slowly: Open the main water shut-off valve very slowly. Listen for any unusual noises and check for immediate leaks.
4. Check for Leaks: Once the system is pressurized, inspect all accessible components for leaks.
5. Manually Run Zones: Turn on each zone manually at the controller. Observe the sprinkler heads to ensure they are functioning correctly and delivering adequate coverage.
6. Adjust and Repair: Make any necessary adjustments to sprinkler heads and repair any leaks or damaged components.
7. Run a Full Cycle: Once everything appears to be in order, run a full watering cycle to ensure the system is operating optimally.

If you encounter significant issues, don’t hesitate to contact an irrigation professional for assistance.

Conclusion

Effectively draining your irrigation system before winter sets in is a vital maintenance task that protects your investment from costly freeze damage. By understanding the process, gathering the right tools, and following a step-by-step approach, you can ensure your system remains in good working order. Whether you choose manual draining with a blow-out or opt for professional help, prioritizing this winterization step will save you time, money, and headaches when spring returns, allowing for a quick and seamless system restart.

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