Two methods are used for irrigation winterization worldwide: the compressed air blowout and the manual/automatic drain method. In Calgary’s climate, only one of them is reliably safe. This guide explains why the blowout method is the Calgary standard — and when drain methods are acceptable.
Blowout vs Drain — Calgary Climate Verdict
| Method | How It Works | Suitable for Calgary? | Freeze Risk |
|---|---|---|---|
| Compressed air blowout | 50+ CFM air clears all zones 3–5 passes | ✅ Yes — standard | NONE (if done correctly) |
| Manual drain | Open drain valves, let gravity drain pipe | ⚠️ Partial only | MEDIUM — low points retain water |
| Automatic drain valve | Pressure-drop triggers automatic drain | ⚠️ Supplemental only | MEDIUM — doesn’t clear backflow or heads |
Calgary’s flat terrain means irrigation laterals don’t consistently drain by gravity — water pools at valve boxes and low points regardless of drain valves. The backflow preventer (mounted vertically) does not drain automatically. The only method that guarantees 100% water clearance from every component is the compressed air blowout. J.G. Irrigation uses a 50 CFM compressor on every Calgary winterization.
Can I drain my Calgary sprinkler system without a compressor?
Manual drain removes water from areas with gravity-favorable slopes but leaves water in horizontal runs, valve bodies, head cavities, and the backflow preventer. In Calgary’s -15°C to -30°C winters, even small water retention causes freeze damage. The compressed air blowout is the only fully reliable winterization method for Calgary. Cost: $90–$160. Call J.G. Irrigation: 587-433-4795.
Professional Blowout — Calgary’s Only Reliable Winterization
J.G. Irrigation — Calgary Irrigation Services
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