Winterizing Your Irrigation System: A Step-by-Step Guide

Why irrigation winterization is critical

When water freezes in irrigation lines it expands with enough force to crack pipe, break valve housings, and ruin sprinkler heads and backflow assemblies. A single freeze event can cause thousands of dollars in repairs that proper winterization prevents. The failures are also hidden, which makes them worse: a split poly lateral or a cracked valve body sits buried all winter and only shows up when the system is pressurized in spring, often after it has been leaking into the yard for days.

When to winterize your system

Schedule winterization after the last watering of the season and before the first hard freeze. Across the Chippewa Valley and the Twin Cities, most systems are blown out between late September and the end of October. The exact date varies by year, which is why getting on the schedule in late summer beats waiting for the first cold night, when every irrigation company in the region is booked.

• Watch the forecast for the first predicted hard freeze, below 28 degrees
• Plan winterization one to two weeks ahead of that date, not the day of
• Shut off the water supply to prevent accidental activation in the meantime
• Factor in system age and any repairs made during the season, since fresh fittings and older pipe are both worth clearing early

What if a freeze arrives before the appointment

An early cold night is usually not a problem. The ground holds heat well into November, so buried pipe is insulated. The vulnerable part is whatever is exposed to open air, which is typically the pipe and backflow assembly coming out of the house. Cover that section with a towel, blanket, or insulated pouch until the appointment. If a hard freeze with single-digit temperatures is forecast first, call and ask to be moved up.

The professional blow-out process

Professional winterization uses high-volume compressed air, not high pressure. Volume is what carries standing water out of long runs and low spots; pressure alone just heats fittings and can damage them. Technicians work systematically through the system one zone at a time, running air until only a fine mist comes from the heads, which is the signal that the zone is clear.

This is the main reason a homeowner shop compressor is not a substitute. Small compressors do not move enough air volume to clear a zone, and running them at high pressure with low volume is how fittings, seals, and gear-drive heads get damaged.

Step by step

• Shut off the supply. Close the irrigation supply valve inside the house or in the pit.
• Drain what will drain. Open manual drains and bleed the backflow device.
• Blow out each zone. Connect the compressor at the designated fitting and run each zone in turn until only mist discharges, then move on. Zones are usually run more than once, since water settles back into low spots.
• Clear the drip zones too. Drip tubing, filters, and emitters hold water like anything else and are included in the blowout.
• Leave valves in the correct position. Technicians set valves so no water can be trapped between them over the winter.

Controller and valve preparation

Set the controller to rain mode or the off position. That preserves the programming, so the schedule does not have to be rebuilt in spring, while preventing the system from trying to run. For added protection, disconnect the controller power supply for the winter, and if the controller has a backup battery, replace it then.

Above-ground components need separate attention. Backflow preventers and any above-grade valves and piping should be insulated, or removed and stored where that is how the system was built. These are the parts that fail first, because they have no soil around them to moderate temperature.

Spring startup checklist

Winterization is half of the cycle. The other half is bringing the system back carefully in spring:

• Restore water pressure slowly to avoid water hammer in empty lines
• Check for leaks at every valve, fitting, and connection before running zones automatically
• Test each zone manually and watch it run
• Adjust heads and coverage patterns, and replace nozzles clogged over the winter
• Reprogram the controller for spring conditions rather than last July's schedule

We winterize and start up systems across the Eau Claire area and the Twin Cities, and startup, a midseason check, and the fall blowout can be bundled so the visits are scheduled automatically each year. See irrigation services, call 888-839-8484, or request a quote.