If you’re booking your first fall irrigation blowout with J.G. Irrigation — or any professional irrigation contractor in Calgary — this checklist explains exactly what happens before, during, and after your winterization appointment. Knowing the steps helps you prepare correctly and ensures nothing is missed that could lead to freeze damage over Calgary’s winter.
Before Your Winterization Appointment
✅ 1. Book Early (August or September)
J.G. Irrigation’s winterization schedule fills rapidly in late September. The safest Calgary winterization window is September 28 – October 10 — before the first hard frost that settles in for the season. Booking in August or early September gives you your choice of date. By mid-October, availability is severely limited. See our full timing guide: when to winterize your Calgary sprinkler system.
✅ 2. Know Where Your Irrigation Shutoff Valve Is
The technician needs to shut off the water supply to the irrigation system before beginning the blowout. This valve is typically:
- In your basement or utility room, on the cold water line branching to the irrigation connection
- Near the water meter
- In a valve box outside near the hose bib (less common in Calgary residential systems)
If you’ve never located this valve, find it before your appointment. If you genuinely cannot locate it, tell J.G. Irrigation when booking — we can help you identify it.
✅ 3. Ensure the Compressor Has Access
J.G. Irrigation uses a large-capacity commercial air compressor (typically 50–85 CFM) on a trailer. The compressor connects to your irrigation system’s blowout port — a quick-connect fitting typically near the backflow preventer on the exterior wall. Ensure the blowout port is accessible and not blocked by vegetation or stored items.
✅ 4. Know Where Your Valve Boxes Are Located
The technician will need to access each zone valve box during the blowout to monitor valve response and check for full zone draining. If your valve boxes are buried under mulch or vegetation, clear them before the appointment. Most Calgary residential systems have one or two valve boxes; larger properties may have more.
✅ 5. Disable Your Smart Controller or Timer
Set your controller to rain delay mode or “off” mode the day before your winterization appointment. This prevents any accidental zone activations that would pressurize a zone before the technician has shut off the water supply and connected the compressor. For Rachio: open the app and set an indefinite rain delay. For Hunter Hydrawise: pause the controller. For standard timers: set the watering days to none, or set the controller to “off.”
During the Winterization: What the Technician Does
✅ 6. Shut Off the Irrigation Water Supply
The first step: close the main irrigation shutoff valve inside your home. This isolates the irrigation system from the pressurized water supply. Without this step, the compressor cannot build pressure in the lateral lines (the supply keeps them topped up). The technician will confirm the valve is fully closed.
✅ 7. Connect the Compressor to the Blowout Port
The commercial air compressor connects to the irrigation system’s blowout port via a quick-connect fitting. This is a dedicated port built into the system at installation specifically for winterization access. If your system doesn’t have a blowout port (older or improperly installed systems), one can be added during the first winterization visit.
✅ 8. Blow Out Each Zone Individually — Multiple Passes
This is the core winterization step. Each zone is activated one at a time while compressed air is injected into the mainline. The air forces remaining water out of the lateral lines and through the sprinkler heads, which pop up and discharge the water as visible spray.
How many passes? J.G. Irrigation performs a minimum of 2–3 passes per zone on the first visit. Some zones require more depending on pipe routing complexity and the amount of water remaining. The zone is complete when:
- The discharge from the heads transitions from water/mist to dry air
- The sound from the compressor changes (pressure stabilizes, less load)
- Head pop-up remains up without water (air-only discharge)
Important: A single pass is not sufficient for most Calgary residential systems. Contractors who perform only one pass per zone are leaving water in the lines that will freeze. J.G. Irrigation’s multi-pass protocol ensures full clearance.
✅ 9. Blow Out Drip Zones
Drip irrigation zones require a different approach — lower compressor pressure and longer dwell time to clear the smaller-diameter distribution tubing and emitters. If your system has drip zones (garden beds, container irrigation), confirm with the technician that these zones are on the blowout sequence. Drip emitters left with water can freeze and crack even if main sprinkler zones are clear.
✅ 10. Drain the Backflow Preventer
After all zones are blown out, the backflow preventer assembly itself must be drained and prepared for winter. For a standard Pressure Vacuum Breaker (PVB):
- Both shut-off valves flanking the PVB body are turned to the 45° (partially open) position for winter. This allows any residual water to drain and prevents the body from holding water that could freeze and crack the brass.
- The bonnet is left in the normal position (not disassembled for winter)
- Some homeowners wrap the PVB body with foam insulation as an extra precaution during extreme cold snaps — this is optional but worthwhile if your PVB is in an exposed location
✅ 11. Set the Controller to Winter Mode
The controller is set to off or program-disabled mode for winter. For smart controllers (Rachio, Hydrawise): the app provides a seasonal shutdown option that preserves all programming for spring reactivation without deletion. The technician will confirm the controller is properly set before leaving.
After Your Winterization: Post-Blowout Checklist
✅ 12. Confirm the Water Shutoff Valve Stays Closed
The irrigation main shutoff valve must remain closed all winter. If it is accidentally re-opened, the backflow preventer and lateral lines can re-fill with water that will freeze. Note the valve location and its closed position so it’s not accidentally turned on by anyone using the utility room.
✅ 13. Check Your Technician Left a Service Summary
J.G. Irrigation leaves a service summary noting: zones blown out, observations about any head or valve issues noted during the blowout, and any follow-up recommendations. Review this summary — if a zone had unusual resistance or a valve didn’t respond cleanly, it’s worth addressing before spring startup.
✅ 14. Book Spring Startup Before You Forget
Many Calgary homeowners book their spring startup immediately after winterization to lock in their preferred date for the following May. Spring startup availability also fills quickly in Calgary. Ask your technician about booking startup at the time of winterization, or contact us online to add yourself to the spring startup list. See our spring startup guide for what to expect.
Common Winterization Mistakes to Avoid
- Waiting too long: The “I’ll do it when the forecast shows frost” approach is too late for booking purposes. By the time you see frost in the forecast, available appointments may be gone. Book in August.
- Turning on the water supply before spring startup: Do not open the irrigation water supply valve in spring without a professional startup. Pressurizing a system that hasn’t been checked for winter damage can cause flooding. Always book a professional startup first.
- Skipping the blowout because “it hasn’t frozen yet”: Calgary’s first hard frost can arrive overnight after a mild stretch. A single overnight at -5°C is enough to freeze and crack irrigation components left with water. Don’t gamble with this.
- Self-service blowout with a consumer compressor: Residential compressors (40-gallon, 5 CFM) do not have sufficient capacity for irrigation blowouts. The volume of air matters more than the pressure. Using an undersized compressor doesn’t clear the lines — it just makes noise while water remains. Professional contractors use 50–85 CFM commercial compressors.
Book Your 2026 Calgary Winterization
J.G. Irrigation is booking fall 2026 winterization appointments now. Call 587-433-4795 or contact us online. Limited slots available in the optimal September 28 – October 10 window — book now to secure your date. We serve Calgary, Airdrie, Cochrane, Okotoks, Chestermere, Langdon, and surrounding communities.
