Proper winterization of your irrigation system is the difference between a smooth spring startup and expensive repairs to cracked pipes and valves. If water remains in the system and freezes, ice expands by 9% and destroys even the sturdiest fittings. Begin preparation 1–2 weeks before the first expected frost.

Step 1: Shut off the water supply

Locate the main shutoff valve for your irrigation system and close it completely. If you have a dedicated irrigation meter, shut that off specifically. Ensure the backflow preventer is also isolated from pressure.

Step 2: Drain the mainline

Open all manual drain valves (e.g., Generic universal ¾" or 1" drain valves) at the lowest points of the system. If your system has automatic drain valves, activate each zone for 1–2 minutes through the controller so pressure drops and the valves open.

Step 3: Compressor blowout

This is the most critical step. Connect an air compressor to the blowout port (typically downstream of the backflow preventer).

Critical parameters

  • Pressure: maximum 50 PSI (3.5 bar) for polyethylene pipes
  • 80 PSI (5.5 bar) is the absolute limit for PVC — NEVER exceed this
  • Volume: 80–100 CFM — sufficient for most residential systems
  • Use a pressure regulator on the compressor for precise control

Zone-by-zone blowout order

  1. Start with the farthest zone from the compressor — the zone with the longest pipe run
  2. Open the zone via the controller and supply air for 2–3 minutes
  3. Watch the sprinkler heads: first water sprays, then mist, then dry air
  4. When only air comes out — the zone is clear, move to the next one
  5. Work from far to near: zone 6 → 5 → 4 → 3 → 2 → 1
  6. Repeat each zone twice for reliability

Warning: never force air into a closed system without an open zone — this can burst a pipe or valve.

Step 4: Insulate above-ground components

  • Backflow preventer — wrap with insulation tape or a dedicated cover
  • Valve boxes — fill voids with foam insulation or dry leaves
  • Main shutoff valve — insulate the pipe and valve from freezing

Step 5: Controller and sensors

Set the controller to "Rain" or "Off" mode, but do not cut power — this preserves the watering program. Disconnect rain and soil moisture sensors if they are not rated for freezing temperatures.

Netafim drip line winterization

Netafim drip lines require gentle blowout — maximum pressure 2 bar (30 PSI). Exceeding this can damage the emitters. Blow out each drip line separately for 1–2 minutes at low pressure. If your system has both spray and drip zones, always blow out drip lines last after reducing the compressor pressure.

How SmartPluvia helps

Open your project plan in SmartPluvia — the zone map shows the blowout order from farthest to nearest. Export a PDF with the zone list and hand it to your crew, or save it as a checklist for next year.