How to Winterize a Sprinkler System: Blow Out vs. Manual Drain (2026)

Frequently Asked Questions

When should I winterize my sprinkler system?

Winterize before the first night that temperatures will stay below 32°F. In most of the US, this means late September to November. Don't wait for the last minute — a surprise early freeze can crack PVC pipes and valves overnight. Check a 14-day forecast and schedule before the first sustained freeze (several nights at or below freezing).

Can I blow out my sprinkler system myself?

Yes, but only if you have a compressor with at least 20 CFM (cubic feet per minute) output at 50 PSI. This is a large compressor — most small portable and contractor compressors produce only 3–6 CFM. Using an undersized compressor blows air at too high a velocity, which can melt or crack plastic fittings. Never use a tank with less than a 20-gallon capacity for blowout work. If in doubt, hire an irrigation company.

What happens if I don't winterize my sprinkler system?

Water left in the pipes expands when it freezes, cracking PVC pipes, poly tubing, and the plastic bodies of valves and heads. A single freeze event can damage 3–5 heads and 1–2 valves — replacement costs $150–$400 for a standard system. In cold climates, failing to winterize once is often enough to write off a season of irrigation repairs.

My sprinkler system has automatic drain valves. Do I still need to blow it out?

Automatic drain valves (also called drain check valves) open when system pressure drops to drain water from the pipes. If your system has them and they're working, a blowout may not be necessary — but confirm by testing: shut off the water supply, run each zone for 30 seconds to drain pressure, then open one of the end-of-zone drain valves. If nothing comes out, the pipes drained. If water flows, the drains aren't working and you need a blowout.

Do I need to winterize a drip irrigation system?

Drip systems are less vulnerable than spray systems because tubing is more flexible than PVC. But head emitters, filters, and pressure regulators can crack in hard freezes. Disconnect and drain drip lines, bring inside any back-pressure valves and inline filters, and insulate any above-ground components left in place.

How much does it cost to winterize a sprinkler system in 2026?

Sprinkler winterization costs by method: Professional blow-out service: $50–$125 for an average residential system (6–8 zones). Most irrigation companies complete a residential blowout in 30–45 minutes. The technician brings a commercial compressor (185 CFM or higher) — far more powerful than any consumer unit. Some companies offer a spring start-up + fall winterization package ($150–$250 total) that's cost-effective if you do it every year. DIY blow-out: compressor rental $40–$80/day (must be 20–50 CFM minimum; larger is better). Compressor purchase: $200–$600 for a unit adequate for irrigation blowout (most homeowners rent). Manual drain method (no compressor): free if your system has manual drain valves installed — just open the valves, let gravity drain the lines, and close the isolation valve. Works well in climates with mild winters or systems with sufficient slope. DIY vs. pro: the main risk of DIY blowout is over-pressurizing the system, which can damage heads and manifolds. If you use a rented compressor, blow each zone for no more than 30 seconds and never exceed 50 PSI for poly pipe or 80 PSI for PVC. Most homeowners in regions with hard winters hire a pro — the $75 service cost is far less than one cracked manifold ($200–$500 to repair).

What size compressor do I need to blow out a sprinkler system?

Sprinkler system blowout compressor requirements: Minimum CFM: 20 CFM for residential systems (8 zones or fewer with standard 1-inch mainline). Recommended: 35–50 CFM for faster, more effective blowout. Professional units: 185 CFM — commercial-grade, clears large systems in one pass per zone. Why CFM matters more than PSI: you need air volume (CFM) to push water out efficiently, not just pressure. A small shop compressor at 150 PSI but only 5 CFM will run for 10 minutes before the tank depletes and barely move water in the pipes. Pressure limits by pipe type: PVC mains — never exceed 80 PSI during blowout. Poly mains — never exceed 50 PSI. Rotary heads — never exceed 50 PSI. Spray heads — never exceed 50 PSI. Technique: blow each zone for no more than 30 seconds, allow 2–3 minutes for the compressor to recover pressure between zones, never run the system dry for more than 30 seconds (the water lubricates the heads). For a typical 6-zone system, the full blowout takes 15–20 minutes plus compressor recovery time. If renting: most equipment rental shops carry 185 CFM towable compressors for $100–$150/day — overkill but completely safe.

Blow-out winterization (using compressed air to clear each zone) is the most effective method and costs $60–$100 if hired out. DIY blowout requires a compressor with at least 20 CFM at 50 PSI — most homeowner air compressors are too small.

A 30-minute winterization protects an investment that can cost $3,000–$8,000 to repair if it freezes.

Method 1: Blow-out (most thorough)

Requirements: Compressor with minimum 20 CFM at 50 PSI. Quick-connect fitting on the blow-out port or main fitting.

Step 1: Shut off the water supply

Locate the main shutoff for the irrigation system — usually inside the house near where the irrigation supply line enters (often near the main water shutoff or in the utility room).

Close the shutoff valve completely.

Step 2: Disable the controller

Set the controller to the “Rain” or “Off” mode, or unplug it. This prevents it from trying to run zones while you’re working.

Step 3: Attach the air compressor

Connect the compressor to the system’s blow-out port (sometimes called the purge valve or quick coupler) — usually a valve between the backflow preventer and the zone valves. Never connect the compressor to the backflow preventer itself.

Step 4: Blow out each zone

Turn on Zone 1 at the controller. Open the air compressor valve slowly and let pressure build in the zone line (target 50 PSI for poly pipe, 50–60 PSI for PVC — never exceed 50 PSI for drip systems). Run until no water vapor exits the heads (10–30 seconds per zone depending on pipe length).

Turn off Zone 1. Wait 5 minutes. Run Zone 1 again — a second pass ensures all water is expelled.

Repeat for each zone.

Safety: Never stand over or near a sprinkler head during blowout — air can eject heads. Never blow out a zone with the zone valve closed — you’ll overpressure the pipe.

Step 5: Blow out the main line

With all zones off, open the system’s main drain valve and run air through the main line to clear it.

Step 6: Protect the backflow preventer

Wrap the backflow preventer (the above-ground device, usually covered in foam insulation) with pipe insulation foam or use a backflow preventer insulation bag.

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Method 2: Manual drain

Works for systems with manual drain valves at the low points of each zone.

1. Shut off the irrigation water supply.
2. Activate each zone at the controller for 5 seconds — this releases pressure in the lines.
3. Open the manual drain valve at the lowest point of each zone. Water will drain by gravity.
4. Let drain for 30 minutes per zone.
5. Close drain valves. Insulate backflow preventer.

This method doesn’t work if the system doesn’t have drain valves, or if the pipes don’t slope consistently to the drain points.

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Post-winterization checklist

• Water supply shutoff: closed
• Controller: set to Rain/Off mode
• All zone valves: closed (or left in the position the controller leaves them)
• Backflow preventer: insulated
• Blow-out port: capped

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Spring startup

When ready to start up in spring:

1. Slowly turn on the main water supply.
2. Walk each zone and check for leaks or damaged heads.
3. Clean and replace any clogged or damaged heads.
4. Reset controller programming and run a full test cycle.

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Related guides

• Sprinkler System Installation Cost — system cost and scope guide
• How to Fertilize Your Lawn — spring lawn care after startup
• Winterize Your Home Checklist — full home winterization
• Annual Home Maintenance Schedule — when sprinkler winterization fits in fall prep