How to Winterize Your Sprinkler System: Step-by-Step

Why Winterizing Your Sprinkler System Matters

Water expands by approximately 9% when it freezes. Any water left inside your sprinkler pipes, valves, or sprinkler heads during winter can crack and rupture components, leading to costly repairs in spring.

When to Winterize

Winterize your sprinkler system before the first hard freeze in your area.

Climate Zone	Target Date
Northern US (Zones 3-4)	Mid to late September
Mid-US (Zones 5-6)	Mid to late October
Southern US (Zones 7-8)	November

Winterization Methods

Method 1: Compressed Air Blowout (Recommended)

This is the most thorough and widely recommended method. A high-volume air compressor forces all water out of every zone, pipe, and sprinkler head.

1. Shut off the water supply: Close the main shutoff valve to the irrigation system.
2. Drain the backflow preventer: Open the test cocks and drain valves on your backflow prevention device.
3. Set the controller to Rain Mode or Off: This prevents the system from trying to run during the blowout.
4. Connect the air compressor: Attach to the system blowout port (usually near the backflow preventer).
5. Blow out one zone at a time:
   • Never exceed 80 PSI for PVC pipe systems or 50 PSI for polyethylene pipe
   • Activate one zone from the controller
   • Run until only a fine mist exits the sprinkler heads (2-5 minutes per zone)
   • Move to the next zone and repeat
6. Drain all remaining water: Open manual drain valves, low-point drains, and any exposed piping.
7. Insulate above-ground components: Wrap the backflow preventer and above-ground pipes with insulation foam.

Method 2: Manual Drain

If your system was installed with manual drain valves, you can drain it without compressed air. This only works if the system has a consistent downward slope toward the drain points.

What NOT to Do

• Never use a home air compressor: You need a compressor rated at 20-50+ CFM at 80 PSI.
• Never exceed 80 PSI: Excessive air pressure can crack sprinkler heads and damage pipes.
• Never stand over sprinkler heads during blowout: Debris can be ejected at high speed.
• Do not skip zones: Every zone must be blown out, including drip irrigation areas.

DIY vs. Professional Blowout

Factor	DIY	Professional
Cost	$50-100 (compressor rental)	$75-150
Risk	Higher — inexperience can damage system	Lower — insured and experienced
Time	2-4 hours for average system	30-60 minutes

Spring Startup Checklist

• Remove insulation from backflow preventer and above-ground components
• Close all drain valves
• Slowly turn on the water supply
• Check for leaks at every sprinkler head and valve
• Reprogram the controller for current watering needs
• Run each zone and adjust sprinkler head direction

Conclusion

Winterizing your sprinkler system is a critical annual task that protects a significant investment. Whether you DIY or hire a pro, the blowout method is the most reliable way to ensure no water remains in your pipes during freezing temperatures.