How to Winterize a Sprinkler System: Zone-by-Zone Checklist

Do You Actually Need to Winterize?

Whether you need to winterize — and how thoroughly — depends entirely on your USDA zone:

The rule: if your area sees ground freezing temperatures, water trapped in pipes, valves, and heads will expand and crack them. A single freeze event can rupture multiple components — typical repair cost: $200–800. Find your USDA zone →

The Three Winterization Methods

Method 1: Compressed Air Blowout (Zones 1–7, recommended)

The most thorough method. Uses compressed air to force all water out of every pipe, valve, and head in the system.

You need: An air compressor with at least a 20-gallon tank, 4–6 CFM at 50 PSI. Many tool rental shops rent irrigation-spec compressors for $40–60/day. Step-by-step:

Shut off the main irrigation water supply valve at the connection to your home's water system

Connect the compressor to the blow-out port (look for a quick-connect fitting near the backflow preventer — most systems have one)

Set the controller to manual mode and activate Zone 1

Open the compressor valve slowly — build pressure gradually to 50 PSI. Never exceed 50 PSI for PVC pipe systems or 80 PSI for polyethylene

Run each zone for 2–3 minutes until no water exits the heads (you'll hear the air sound change from wet to dry)

Repeat for each zone — do each zone twice. After the first pass, moisture remains in low spots; the second pass clears it

Blow out the main line last — open the manual drain valve (if present) and blow back toward the backflow preventer

Disconnect the compressor and cap the blow-out port

Insulate the backflow preventer with foam pipe wrap rated to your local minimum temperature

Critical safety note: Never stand over a sprinkler head during blowout. Compressed-air discharge from a rotor head can cause injury. Stand to the side.

Method 2: Manual Drain (Zones 5–7, where blowout equipment isn't available)

If your system was installed with manual drain valves at the low points of each zone line, you can drain by gravity without a compressor.

Step-by-step:

Shut off the main irrigation supply

Open each manual drain valve (typically at the lowest point of each lateral line)

Open the sprinkler heads in each zone manually to release air locks that prevent draining

Wait 20–30 minutes for gravity drainage to complete

Close all drain valves

Insulate any above-ground components

Limitation: Manual draining doesn't remove water from the heads themselves or from mid-line low spots. Not recommended for Zone 5 and colder — blowout is more thorough.

Method 3: Automatic Drain Valves (all zones, where installed)

Some systems include automatic drain valves that open when system pressure drops below 8–10 PSI — meaning they drain automatically when you shut off the water. If your installer included these, the winterization process is:

Shut off main supply

Manually activate each zone for 30 seconds to exhaust pressure

Insulate above-ground components

Verify your system has these before relying on this method — not all installers include them, and they can fail over time.

Zone-by-Zone Winterization Checklist

Zones 1–5: Full Blowout Required

• [ ] Schedule blowout before first forecast frost (typically September for Zone 4, October for Zone 5)
• [ ] Rent or hire a compressor — minimum 20-gallon tank, 4–6 CFM
• [ ] Blow out each zone twice (first pass clears most water, second pass clears remaining moisture)
• [ ] Insulate backflow preventer with foam wrap rated below your local minimum temp
• [ ] Shut off and drain the controller's main water supply line
• [ ] Set controller to "off" or "rain delay" for the season
• [ ] Check Rachio 3 or B-hyve app for freeze alert settings — enable winter mode

Zones 6–7: Blowout or Manual Drain

• [ ] Check extended forecast — blowout before first sustained frost forecast
• [ ] Blowout preferred over manual drain for Zone 6 and colder parts of Zone 7
• [ ] Insulate backflow preventer
• [ ] Shut off main irrigation valve
• [ ] Leave controller in "rain delay" rather than fully off — easier to run a test cycle in a spring warm spell

Zones 8–9: Partial Winterization

• [ ] Shut off main irrigation supply before temperatures drop below 32°F
• [ ] Insulate any above-ground components (backflow preventer, above-ground valve boxes)
• [ ] No blowout typically needed — light frosts don't penetrate deep enough to damage underground pipes
• [ ] Reduce controller schedule from October — grass growth slows, water needs drop significantly

Zones 10–13: Seasonal Schedule Change Only

• [ ] No freeze protection needed for the irrigation system itself
• [ ] Adjust watering schedule for cooler temperatures and reduced evapotranspiration
• [ ] Smart controller users: enable seasonal adjustment mode (Rachio and B-hyve both have this)
• [ ] Inspect heads for dry-season blockage before ramping back up in spring

When to Winterize: Timing by Zone

The general rule: winterize when you see the first forecast of temperatures below 32°F that will last more than one night.

Smart controller tip: Both the Rachio 3 and Orbit B-hyve send freeze notifications — the Rachio 3 will alert you when a watering cycle is scheduled within 24 hours of a forecast freeze. Use this as your signal to run the seasonal blowout.

Spring Start-Up: What to Do After Winter

When temperatures reliably stay above freezing:

Inspect all heads for cracking or movement from ground frost

Open the main valve slowly — sudden pressure can stress connections loosened by winter ground movement

Run each zone manually for a full cycle and walk the zone to check for coverage gaps, pooling, or misting heads

Check controller settings — batteries may have discharged; reset your schedule

Test the backflow preventer — turn on slowly and check for leaks at the fitting

Allow 2–3 weeks of spring operation before fine-tuning the schedule for summer — the Rachio 3's Flex Daily mode recalibrates automatically.

Common Winterization Mistakes

Mistake: Waiting until after the first hard freeze The damage is already done. Winterize at the forecast of the first sustained frost, not after it arrives. Mistake: Only blowing out once One blowout pass leaves moisture in low spots and head bodies. Always do two passes per zone. Mistake: Exceeding 50 PSI during blowout PVC pipe joints crack above 50 PSI of compressed air pressure. Set your compressor regulator before starting. Mistake: Forgetting the backflow preventer It's above ground, exposed to ambient temperature, and has the most water-trapping capacity of any component. Insulate it every season. Mistake: Leaving the controller fully programmed If your controller malfunctions in winter and activates a zone with the supply shut off, it can damage the pump or valve. Set to "off" or "rain delay."

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Related guides:

• Best Sprinkler Systems for Cold Zones →
• Rachio 3 Review — Freeze Alert Feature →
• USDA Zone Guide — Find Your Zone →

This guide reflects standard irrigation industry practice and EPA WaterSense recommendations. Local plumbing codes vary — check municipal requirements for backflow preventer maintenance.