How to Winterize a Sprinkler System in Calgary — DIY Steps and When to Call a Professional

Calgary homeowners who want to winterize their sprinkler system correctly face a fundamental equipment constraint: the compressed air blowout step requires a 185 CFM commercial-grade compressor that is not available for rent at standard Calgary tool rental locations. This guide covers what DIY winterization steps you can do yourself, why the blowout requires equipment that most homeowners cannot access, and how to decide between DIY and professional service for your specific system.

The 4 Steps to Winterize a Calgary Sprinkler System

Step 1: Close the Main Irrigation Shutoff Valve

Locate the main irrigation shutoff valve (typically in the mechanical room or basement near the water meter) and turn it to the fully closed position. This stops new water from entering the system. This step can be done by any homeowner without equipment. Close the shutoff at least 30 minutes before the blowout to allow residual pressure to equalize.

Step 2: Perform the Compressed Air Blowout (Professional Required)

The blowout step is where DIY Calgary winterization most commonly fails. The Irrigation Association specifies 185 CFM (cubic feet per minute) as the minimum compressor capacity for residential irrigation blowout. Standard tool rental compressors in Calgary deliver 85 to 110 CFM. At that volume, air exits the heads nearest the compressor connection but does not maintain sufficient velocity through the full lateral run to carry water out of the far sections. The result looks like a successful blowout but leaves water in the middle and far sections of the lateral lines. A 185 CFM compressor is a large tow-behind commercial unit not available at most Calgary tool rental locations. If you cannot confirm a rental compressor delivers 185 CFM sustained, professional blowout is the only way to protect your Calgary system.

Step 3: Drain the Backflow Preventer

After blowout, locate the two test cocks on top of the brass RPZ assembly and rotate each to approximately 45 degrees (perpendicular to the pipe direction). This opens the test cock ports and allows water in the preventer body to drain. Leave the test cocks in the 45-degree position for winter. The professional blowout technician does this automatically as part of a complete winterization visit.

Step 4: Set the Controller to OFF

Set the irrigation controller to the OFF or SEASONAL mode that completely disables all automatic and manual zone activation. Do not use RAIN DELAY — a rain delay will expire after the set number of days and resume automatic watering. Full OFF mode prevents any zone activation for the winter.

When Professional Winterization Is Necessary in Calgary

• Always for the compressed air blowout step — unless you own or have confirmed access to a 185 CFM commercial compressor
• When the main irrigation shutoff valve location is unknown or inaccessible
• When the backflow preventer location is unknown, inaccessible, or shows visible damage
• When you want written documentation of completion for insurance purposes

For professional Calgary sprinkler system winterization with a 185 CFM commercial compressor, IA-certified technicians, and a written service receipt, call J.G. Irrigation at 587-433-4795. Visit our irrigation winterization page to learn more about our fall blowout service.