Steps to Winterize Irrigation Systems in Michigan

Winterizing an irrigation system in Michigan is an annual, nonnegotiable task for property owners who want to avoid frozen pipes, split fittings, damaged backflow assemblies, and expensive spring repairs. Michigan winters bring repeated freeze-thaw cycles, hard ground freezes, and extended subfreezing periods that can trap water inside lines and valves. This article gives a detailed, practical, step-by-step guide for do-it-yourselfers and property managers, covers equipment and safety, explains special considerations for wells and municipal supplies, and shows how to bring a system back online safely in spring.

When to Winterize in Michigan

Timing is critical. Waiting too long risks a freeze; doing it too early can interfere with late-season overseeding or irrigation needs.
Plan to winterize when the forecast shows sustained nightly lows near or below 32 degrees Fahrenheit and daytime highs are not consistently above 40 F. In most parts of Michigan this means preparing in late October to mid-November, but southern counties may be later and northern/upstate areas earlier.
Key signs that it is time:

Fall temperatures routinely drop below freezing at night.
Turf and plants no longer require regular irrigation.
First light hard freeze or heavy frost has occurred and more are expected.

If you are unsure, monitor a 7-10 day forecast and act before the first prolonged cold snap.

Methods of Winterizing: Overview

There are three common methods to remove water from irrigation systems:

Manual drain: opening low points and drain valves so water exits by gravity.
Automatic drain systems: valves that open when pressure drops and drain water automatically.
Compressed-air blowout: forcing compressed air through each zone to purge water.

In Michigan the typical best-practice is a compressed-air blowout for in-ground systems because it reliably removes most water from lines and heads. Manual drains and automatic drains can work but are less reliable in low-lying lines, long lateral runs, and complex systems. Antifreeze is rarely used and, if used, requires adherence to strict local and environmental rules–automotive antifreeze is toxic and must not be used.

Tools and Supplies You Will Need

Before starting, gather the right tools. Having the correct compressor, fittings, and safety gear reduces risk of damage and injury.

Air compressor capable of delivering controlled pressure. Typical recommended pressure range: 50-80 psi. Flow needs vary by system size; many small systems can be done with 6-12 CFM, while larger systems perform best with 10-20 CFM. Do not exceed 80 psi on plastic pipes and heads unless system specifications allow it.
Quick-connect blowout adapter sized to your irrigation system (usually 1/2″ or 3/4″).
Pressure regulator and quick-connect fittings.
Safety glasses and hearing protection.
Hand tools: adjustable wrench, screwdriver, channel-lock pliers.
Towels or rags for cleanup.
Insulation materials: foam pads, insulating tape, insulation box or wrap for the backflow preventer.
Shop vacuum or wet/dry vac if you prefer to use suction for specific sections (optional).
Marker and labels to mark zones and valves.

Step-by-Step Winterization Procedure (Blowout Method)

Follow these steps exactly, leaving a short pause between each action to confirm pressure and flow behavior.

Turn off the water supply to the irrigation system at the main shutoff. For municipal supplies this is usually a valve near the meter. For well systems, shut off the irrigation line at the pressure tank or main isolation valve. Confirm no water flow by turning on a sprinkler zone briefly before proceeding.
Shut off the controller (clock) or put it into manual/rain mode to prevent it from calling zones while you work. Remove the battery backup if desired to prevent controller activation. Note any scheduled late-season watering needs before you turn it off.
Open all manual drain valves and low points in the system. Also open the blowout port (if installed) and any vacuum relief valves. This lets trapped water drain out before applying air.
Connect the compressor to the system using a pressure regulator and the correct quick-connect adapter. Set the regulator to a conservative starting pressure of about 40-50 psi. You will gradually increase up to a maximum of 80 psi only if needed and if your system is rated for it.
Work zone by zone. On the controller, manually activate the first station while the compressor supplies air. Keep the compressor running and watch the sprinklers pop up. Air will purge water; after a few minutes you should see water sputter and then stop with mostly air coming through.
Move through every zone. After air has been running for 1-3 minutes per zone (more for long lateral lines), stop that station and move to the next. Ensure each zone is purged until clear air and no water mist exit the sprinkler heads. For long runs allow additional time; large systems may require 2-5 minutes per valve.
After all zones are purged, turn off the compressor and disconnect. Leave manual drain valves open, all low points open, and the main shutoff in the off position. If you have an automatic drain system, confirm drains are open and clear.
Drain and purge drip lines separately. Drip systems should be purged with lower pressures (20-30 psi) and for short bursts to avoid blowing emitters off. Alternatively, remove drippers and store them inside.
Protect above-ground components. Insulate the backflow preventer with a well-fitting insulated cover or remove the device and store it indoors if allowed. Wrap exposed valves, the controller, and any exposed piping in foam or insulating tape, and use a winter blanket for meters or other equipment.
Close all service drains after they have drained and new frost has set in if local practice calls for it–check local plumbing code. Document the date and condition of the system.

Safety and Pressure Guidelines

Never exceed 80 psi unless system parts are rated higher. Excessive pressure can damage sprinkler heads, seals, valves, and PVC pipes.
Keep the compressor set up on stable ground; wear eye and ear protection.
Use a pressure regulator and a gauge between the compressor and irrigation system so you can accurately control PSI.
Avoid connecting shop compressors with very low CFM to large systems because they may overheat or deliver insufficient airflow. If you are unsure, hire a professional.

Special Cases: Wells, Backflow Preventers, and Drip Systems

Well Systems: Isolate the irrigation feed at the pressure tank or a dedicated shutoff. You may need to turn off the well pump or install an air admittance device per local codes. Be cautious of pressure tank settings.
Backflow Preventers: A common source of costly winter damage. If the backflow device is above ground and removable, take it indoors and store it in a heated area. If it is fixed, drain it completely, open test cocks and plugs, and wrap it with an insulated cover specifically designed for backflow assemblies.
Drip Irrigation: Emitters and microtubes are delicate. Purge with low pressure or remove emitters. Some professionals recommend removing low-voltage solenoids for valves on drip zones and storing them inside.

Common Mistakes to Avoid

Using automotive antifreeze: Never use ethylene glycol or standard automotive antifreeze in an irrigation system. It is toxic and harmful to soil, plants, pets, and groundwater. Only use irrigation-approved, non-toxic antifreeze where permitted and recommended by local authorities.
Over-pressurizing: Applying too much air pressure is one of the most common causes of damage during blowouts.
Skipping the backflow: Backflow assemblies are expensive and vulnerable; failing to protect them is a frequent and costly oversight.
Forgetting to set the controller to off/rain mode: A single accidental schedule start during the blowout can send a zone full of pressurized air into an unintended area and cause damage.

Hiring a Professional: When to Call a Pro

Consider hiring a licensed irrigation professional if any of the following apply:

You do not have access to a suitable compressor or fittings.
Your system is large (many zones and long laterals) or complex (multiple backflow assemblies).
You have limited hands-on experience with valves, blowouts, and backflow devices.
You prefer a warranty or insurance that most pros carry.

Typical cost for a professional blowout service in Michigan varies by system size and region but often ranges from about $75 to $250. Get written estimates and confirm the contractor uses regulated pressure and documents completion.

Spring Reactivation and Inspection

When warming weather returns, reactivate the system carefully.

Inspect all visible piping, heads, and the backflow device for cracks or leaks.
Close all manual drains and ensure the main shutoff is in the on position.
Start the controller at low pressure or with the main valve partially open to slowly pressurize the system–do not fully reopen to full pressure immediately.
Test one zone at a time and visually inspect for leaks, broken heads, and misaligned nozzles.
Check the backflow preventer and have it tested, as required by local codes.
Replace batteries in controllers and reprogram schedules only after testing is complete.

Final Checklist

Before you finish winterizing, make sure you have:

Shut off and locked the water feed.
Drained or blown out each zone until clear air exits.
Insulated or removed backflow preventer and exposed components.
Turned the controller to off/rain mode and recorded work performed.
Stored tools and compressor safely and labeled any valves or zones for spring.

Winterizing irrigation systems in Michigan protects your investment and reduces the chance of expensive spring repairs. With careful timing, the right tools, and methodical zone-by-zone work–especially using a controlled blown-air method–you can safeguard your pipes, valves, and backflow assembly from freeze damage. When in doubt, consult or hire a licensed irrigation professional to ensure the job is done safely and effectively.