How to Winterize Your Irrigation System

By Robert Robillard on Home Maintenance

How To Winterize Your Irrigation System

The “Blow Out” Method to Winterize Your Irrigation System

If you live in a cold climate you need to consider taking precautions to avoid damage to your irrigation system.  This article will show you how to winterize your irrigation system and save you hundreds of dollars by teaching you how to do this procedure yourself.

Why Winterize?

Irrigations systems are susceptible to freeze damage.  Even if you have drained the water out of your irrigation system, some water remains in the valve and pipe and can freeze, expand, and crack.    In the northeast we primarily use Polyethylene pipe on our irrigation systems.  Polyethylene is a black, flexible pipe and does expand slightly under pressure.   Even with its flexible characteristic water left inside a poly pipe can freeze and rupture the pipe walls.

Freezing water in the Pressure Vacuum Breaker [back-flow prevention assembly]  will split or rupture the copper or brass housing and internal component .

There are three methods of winterizing an irrigation system:

  1. Manual drain
  2. Auto drain
  3. Blowout

This article and video addresses blowing out a system with a compressor.  We feel it is the best practice in irrigation systems located in regions of the country where the frost level extends below the depth of the irrigation pipes.

Every year, before the first freeze, the ritual of irrigation “blow out” becomes the priority for all irrigation systems in regions located where the frost level extends below the depth of installed piping.

Blow Out Method

The blow out method utilizes an air compressor with a 800 to 100 Cubic Foot per Minute (CFM) rating.  My compressor has a 33 gallon tank and is perfect for my large 6-zone system.  My neighbor uses a 6-gallon compressor for his small 2-zone system.    Either compressor is fine for a system that has a water mainline of 2-inches or less.  My system as a 1-inch mainline.

Location of Connection

If possible try to locate your air hose connections after the PVB back-flow device as compressed air can damage the PVB back-flow device.


pressurevacuumbreakerPressure Vacuum Breaker [PVB]

A  pressure vacuum breaker is used on irrigations systems to protect water supplies from contamination or pollution.

Irrigation back-flow devices are designed for installation on potable water lines to protect against both back siphonage and back pressure of contaminated water into the potable water supply.



How To Winterize Your Irrigation System

Compressor quick coupler, and two sided threaded connector

How To Winterize Your Irrigation System

quick coupler, and air hose attached to PVB


Two Compressor Attachments

To minimize the risk of freeze damage, you’ll need to winterize your irrigation system blowing air through the pipes to push all of the water out of the lines.   The compressor attaches to the irrigation system Pressure Vacuum Breaker [PVB]  via a quick coupler, or a hose bib.

How To Winterize Your Irrigation System

Hose bib connector


How To Winterize Your Irrigation System

Washing machine hose, quick coupler, barbed fitting, and pipe clamp make up a hose bib connector

Making Your Own Compressor Attachment

How To Winterize Your Irrigation System
Hose bib connector attached to air hose

Steps to Winterize an Irrigation System

The first step is to shut off the irrigation water supply.   Typically this shut off is near the main water meter entering the house.  You may have to trace the pipe back fro the PVB to locate the shut off ball valve or other valve.

After the water is shut off, you should drain the inside water line.  Most systems, have a drain plug, or sill cock drain to drain and dry the water line.   I open this valve and drain the pipe into a small bucket.  Water will come out but in order to completely drain this line, you will need to open either the sill cock valve or a test cock on the PVB [house side] to allow the pipe to completely drain.

Once this pipe is drained go outside and close the back-flow isolation valves to isolate the water supply line to house.  Open and drain the test cocks on the PVB

Using your connectors attach your compressor to the system [irrigation system side of PVB]  to either a sill cock or a test cock, depending on your system.  Keep the valve in the closed position, as you attach the air compressor hose to the fitting.  It is important not to run a compressor without an open valve, as the compressed air can damage a zone valve gate.

The next step is to turn on and activate the sprinkler zone station on the controller.  Turn on the zone that is highest in elevation and the furthest from the compressor.

Slowly open the valve on the compressor; to allow air into the irrigation system.  The rule of thumb is to let the air run through each zone for 2-minutes.  I typically do a minute or less and repeeat after the compressor has had time to recover and charge up the tank.

Each station/zone should be activated until no water can be seen exiting the heads, I suggest that you repeat the whole process a few times to ensure the maximum amount of water has been evacuated from the system.  With smaller compressors this may take longer.

After the water has been evacuated from the irrigation lines, disconnect the air compressor and release any air pressure that may be present in the lines.   Then open and drain the all of test cocks again on the PVB to ensure water has drained.

The final step is to open and close the isolation ball valves on the PVB  back-flow device a few times to ensure that any trapped water has escaped from the upper areas.   Finally, turn and leave these valves  at a 45˚ angle, this is a half open position and will allow any moisture to drain.  Open the test cocks and leave these valves like this for the winter.

Irrigation Blowout Video Step by Step:

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About the author

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzz As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising the bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob

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