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When to Winterize Your Sprinkler System (Blowout Date by ZIP)

Enter your ZIP to see when to blow out your sprinklers before the first freeze, the air pressure your pipe can take, and what a pro blowout costs.

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ZIP code
Pipe type

Blowout fittings and a backflow cover

Winterize Sprinkler System Blow Out Adapter: Air Compressor to National Pipe Threads (NPT) Set with Shut Off ValveThreads into the blowout port, with a valve to meter the airCheck price on Amazon →
Vibrant Yard Co. Sprinkler Winterize Blow Out Adapter, Lead-Free Brass Quick-Connect Plug to Garden HoseFor a system with a garden hose thread connectionCheck price on Amazon →
Cholila Cover Insulated Backflow Preventer Pipe Pouch, 16W x 20H inCovers the backflow preventer on freezing nightsCheck price on Amazon →

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Sprinkler blowout dates, pressure, and cost

Typical first freeze by city

Blow out before the first 32°F night. The hard freeze is the last call.

Swipe sideways to see every column.

CityFirst freeze, 32°FHard freeze, 28°F
Denver, COOct 9Oct 19
Minneapolis, MNOct 13Oct 25
Salt Lake City, UTOct 26Nov 6
Detroit, MIOct 25Nov 5
Boston, MAOct 29Nov 9
Chicago, ILNov 2Nov 12
St. Louis, MONov 1Nov 11
Atlanta, GANov 11Nov 24
New York, NYNov 19Nov 30
Dallas, TXNov 25Dec 8

Median dates from NOAA's 1991-2020 climate normals for the city's ZIP prefix. Half of years freeze earlier than this.

Blowout pressure by pipe

Too much air cracks fittings. Stay at or under the cap.

Swipe sideways to see every column.

PipeMax air pressure
Rigid PVC (white or gray)80 PSI
Flexible poly (black)50 PSI
Not sure, or a mix50 PSI

Caps from Colorado State University Extension and Hunter. Hunter adds that the pressure must stay under the lowest-rated part in the zone, which is why a mixed system gets the poly number.

Why the backflow preventer goes first

It sits above ground, so it freezes before the pipe does.

  • Soil insulates the buried lines, so one early frost rarely hurts them. The backflow preventer and any pipe above ground take the cold first.
  • Water grows by about one eleventh when it freezes (Colorado State Extension), enough to crack a brass backflow body (Hunter).
  • Missed the date? Wrap the backflow preventer with an insulated cover or towels on freezing nights until the system is blown out.

Frequently asked questions

When should I winterize my sprinkler system?

Before the first freeze. Hunter, the sprinkler maker, says to blow out every year before the first freeze wherever frost reaches the pipe. In a typical year the first 32°F night comes around Oct 13 in Minneapolis, Nov 2 in Chicago and Nov 25 in Dallas (NOAA 1991-2020 normals). Enter your ZIP above for yours.

What PSI should I use to blow out sprinklers?

No more than 80 PSI for rigid PVC pipe and 50 PSI for flexible black poly pipe, per Colorado State University Extension and Hunter. If you don't know your pipe, or it is a mix, stay at 50 PSI.

What size air compressor do I need to blow out sprinklers?

Colorado State Extension's rule is the largest zone's gallons per minute divided by 7.5 for the minimum CFM, but volume matters as much as pressure. Contractors run 80 to 100 CFM machines (HomeGuide), and the University of Minnesota says most home compressors reach the pressure but not the air volume. Home Depot rents a 185 CFM tow-behind for about $159 for 4 hours.

How much does it cost to winterize a sprinkler system?

HomeGuide puts a pro blowout at $50 to $150 for up to 12 zones, plus $5 to $10 for each zone past that. Angi's national average is $93, from 8,225 projects.

How long do I blow out each zone?

Two short runs of about 2 minutes each, until only a fine mist comes out of the heads. Colorado State Extension says two short cycles beat one long one, and Rain Bird says not to run a zone more than 2 minutes at a time, because dry rotor heads heat up.

Can I just drain the system instead of blowing it out?

Only if you know the drain valves sit at the low points of every line. Hunter allows manual draining in that case. Colorado State Extension is stricter: it says not to trust drain valves, and that systems with electric valves must be blown out with air.

Do I blow air through the backflow preventer?

No. Colorado State Extension says pressure vacuum breakers and reduced pressure devices must never be blown out with compressed air, and Hunter says not to blow through a backflow device or a pump. Connect at the blowout port after it, then leave its ball valves half open for winter.

Do I need to winterize sprinklers in a warm state?

Not with a full blowout if your ZIP doesn't get a 32°F night in a typical year. The pipes underground stay safe there. The parts above ground, mainly the backflow preventer, can still crack on a rare hard freeze, so wrap them on those nights.

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