Steps to Winterize Your Colorado Irrigation System

Winter in Colorado can be brutally cold and unpredictable. Properly winterizing your irrigation system protects pipes, valves, backflow devices, and emitters from freeze damage and costly repairs in spring. This guide gives clear, step-by-step instructions tailored to Colorado conditions, practical equipment recommendations, common pitfalls, and verification tips so you can leave your system ready for months of sub-freezing temperatures.

Why winterization matters in Colorado

Colorado’s elevation and continental climate produce wide temperature swings and recurring hard freezes from late fall through early spring. Water left inside irrigation lines, valves, or backflow assemblies expands when it freezes and can crack PVC, ruin sprinkler heads, and damage underground fittings. Municipal requirements and local plumbing codes often require backflow devices to be winterized or removed. Taking methodical steps now prevents emergency repairs, lawn damage, and repeated irrigation failures when you restart the system.

Know your system before you start

Before you begin, identify the main components and how your system is controlled. This determines the best winterization method and avoids accidental damage.

• Controller (timer): battery backup? removable faceplate?
• Valve type: manual ball valves, solenoid valves, zone valves.
• Backflow preventer: atmospheric vacuum breaker, pressure vacuum breaker, double-check, RPZ.
• Water source: municipal domestic supply versus well or irrigation ditch.
• Sprinkler types: spray heads, rotary rotors, drip lines, micro-sprays.
• Mainline materials: PVC, polyethylene, copper.

Recording these details helps you choose pressures, sequence, and whether you can use the compressed-air blowout method safely.

Tools and supplies you will need

Have these items on hand before you start to avoid delays and reduce risk of damage.

• Air compressor with regulator: 20-50 psi usable range; 10-15 CFM is ideal for larger systems. Smaller compressors work for small residential systems.
• Blowout adapter kit: quick-coupler connection that matches your irrigation system service port.
• Pressure regulator or inline air regulator: essential to control psi going into the irrigation lines.
• Safety gear: eye protection and hearing protection.
• Wrench set, screwdriver, pliers for valves and electrical disconnect.
• Shop vac or wet/dry vacuum (optional) for siphoning low spots and valve boxes.
• Pipe plugs and drain caps for low points and drains.
• Marker, notebook, and camera to document irrigation zone IDs and valve positions.

Note: Do not use a compressor without a regulator. Excessive pressure is the most common cause of broken sprinklers and ruptured pipe during blowout.

Two accepted winterization methods and when to use them

There are two common ways to winterize: manual drain or compressed-air blowout. Choose based on system type, access, local code, and your comfort level.

Manual drain method

This method is safest for all systems and recommended when you have accessible manual drain valves and no compressor.

• Turn off the water supply and shut off the controller.
• Open all manual drain valves, low-point drains, and drip line drains.
• Open test ports or manual gate valves to allow trapped water to escape.
• Remove and drain backflow preventer or follow manufacturer instructions to drain it.
• Open or remove the controller faceplate and remove batteries.
• Leave valves open to allow residual water to drain by gravity.

Manual draining is slower but less risky for older PVC or fragile components and complies with many local codes.

Compressed-air blowout method

Blowing out each zone with compressed air is quicker and standard in Colorado for large systems, but it requires care and lower pressure for drip systems.

• Set regulator to 30-50 psi for standard spray and rotor heads. 40 psi is a common safe starting point.
• For drip and micro-spray systems, use 20-30 psi to avoid damaging emitters and tubing.
• Connect the compressor to the irrigation system using the blowout adapter. Ensure all connecting tools are tight and leak-free.
• With the controller turned off, manually actuate each zone solenoid using the controller’s manual station or by jumping the solenoid.
• Run each zone 1.5-3 minutes or until only dry, sandy air emerges from sprinkler heads; longer for zones with long lateral runs or heavy saturation.
• Close the zone and move to the next.

If you hear or see water surging or hammering, stop immediately and reduce pressure. Never exceed manufacturer-recommended pressures for any component.

Step-by-step winterization checklist (recommended sequence)

1. Shut off the main water supply to the irrigation system and close any isolation valves.
2. Turn off electric power to the controller and remove batteries. Label and store batteries indoors.
3. If you have a backflow preventer that can be drained in place, follow the manufacturer’s steps. If required by code or advisable because of persistent freezing, remove and store the backflow assembly in a heated area.
4. Open all manual drain valves and low-point drains to let gravity expel residual water.
5. If using the blowout method, attach the blowout adapter and set regulator to appropriate pressure for that zone type (20-30 psi for drip; 30-50 psi for sprays/rotors).
6. Manually run each zone until air runs clean and dry from the highest sprinkler head or until no water is seen exiting.
7. Close zone valves, leave manual drain valves open, and install pipe plugs in low points if possible.
8. Insulate above-ground risers, exposed valves, and backflow devices with foam covers and insulating tape.
9. Cap or wrap the controller and store any removable sensors or rain shutoff devices indoors.
10. Run a final site inspection to ensure valve boxes are draining, there are no pooled areas, and all components are stored or insulated.

Leave a clearly labeled note in or near the controller with the date of winterization and the pressure used if you used a compressor; this helps the technician who restarts the system in spring.

Backflow devices and legal requirements in Colorado

Backflow preventers protect municipal water supplies, and many Colorado jurisdictions require they be winterized or removed and tested annually. Common options:

• Remove the device and store it indoors if it is above grade.
• If removal is impractical, drain according to manufacturer instructions and insulate the assembly with preformed insulation covers and heat tape where permitted.
• Check with your local water authority for specific winterization and testing rules, as failure to comply can lead to fines or service interruption.

Always keep a record of the last test date and winterization method used.

Common mistakes and how to avoid them

• Using excessive compressor pressure: Always use a regulator. Excess pressure can split sprinklers and pipes.
• Blowing out a system with the main water still on: This forces pressurized municipal water into the system and can damage components. Turn the main off first.
• Forgetting to drain the backflow: Backflows often sit higher than the rest of the system and are a common failure point.
• Not removing batteries from the controller: Batteries can corrode and leak over winter. Remove and store indoors.
• Skipping repairs: Fix visible leaks, broken heads, and misaligned nozzles before winter so you don’t lock damage into the system.

Insulation and small-prep items that extend protection

• Insulated valve box covers reduce freeze cycles inside valve boxes.
• Foam covers for backflow devices and above-ground valves prevent wind-chill damage.
• Heat tape is rarely needed in Colorado if devices are buried below frost line, but can be used on critical above-ground assemblies where local code permits.
• Clear plastic and burlap wraps are useful for protecting exposed electronics but should not trap moisture.

Spring startup notes and verification

Documenting your winterization makes spring startup smoother. When restarting:

• Inspect for cracks in PVC, damaged heads, and valve bodies.
• Close all manual drains and reinstall removed parts like backflow assemblies following manufacturer torque specs.
• Pressurize the system slowly and inspect for leaks at joints and fittings.
• Run each zone and check coverage and pressure. Replace nozzle heads if necessary for uniform distribution.

If issues arise at startup, address small leaks early. A small repair now is cheaper than replacing a burst mainline or backflow device.

When to call a professional

Hire a licensed irrigation or plumbing professional if:

• You are uncomfortable using a compressor or dealing with pressurized systems.
• Your backflow device is complex or located where you cannot properly drain it.
• The system has had previous freeze damage or extensive underground leaks.
• Local code requires a certified technician for backflow testing and winterization.

A pro can also perform a thorough end-of-season inspection and document compliance with local water authority requirements.

Final practical takeaways

• Plan winterization before consistent nightly freezes begin; in much of Colorado that means late September through October depending on elevation.
• Use a regulator and conservative pressure: 30-40 psi is a safe middle ground for most systems; 20-30 psi for drip.
• Drain or remove the backflow preventer and store electronics and batteries indoors.
• Document everything: pressure used, dates, and any repairs.
• When in doubt, hire a licensed irrigation professional.

Winterizing your Colorado irrigation system is an annual investment that prevents major headaches and protects your landscape. With the right preparation, tools, and sequence of steps, you can keep your irrigation system intact and ready to spring back to life when the snow melts.