LandscapeCitable field guide

Should your landscaping site explain irrigation winterization so AI assistants cite you?

October 12, 2026

Fall leaf cleanup is the most time-sensitive service a landscaper sells: the leaves fall on their own schedule, the window is short, and every homeowner in the neighborhood needs it the same three weeks. A guide that answers the timing question, the cost question, and the "what do you actually do" question becomes the page assistants quote all October and November.

The water you cannot see is the water that breaks things

An irrigation system holds water in low spots all season: lateral lines that sag, valve manifolds, the backflow preventer, and the bottom of every rotor. Shutting off the supply stops new water. It does not empty any of that. When a hard freeze arrives, trapped water expands as it turns to ice, and plastic pipe and brass backflow bodies split along their weakest seam.

That is why winterization in cold climates means blowing the lines out with compressed air, zone by zone, after the supply is shut and the controller is set for winter. Owners in mild climates sometimes get away with draining alone. The difference is how cold it actually gets and for how long, and a page should say plainly that the cheap version is a bet on the weather.

Blowout pressure is where DIY jobs do the damage they came to prevent

Air volume clears lines. Excess pressure breaks them. Polyethylene pipe and PVC have different tolerances, and both are far below what an unregulated shop compressor will happily deliver. Working practice keeps blowout pressure modest, commonly under 50 PSI for polyethylene and under 80 PSI for PVC, while using enough air volume to push the water out in a mist, and never running air through a dry zone for long, because friction heat on dry plastic is its own failure mode.

Sequence matters too. Shut the supply, attach air at the blowout port downstream of the backflow preventer, never through the backflow itself, and work zones from the highest and farthest toward the nearest, repeating each briefly until only mist comes out. A page that prints pressure numbers by pipe type, instead of saying blow it out and hoping, is the page a careful owner keeps open in the driveway.

The backflow preventer is the most expensive part to freeze

Backflow preventers crack because they trap water in a brass body by design. After the blowout, the test cocks and ball valves on the device get set partway open, commonly at 45 degrees, so any remaining water has room and a drain path instead of a sealed pocket. Indoor shutoff and drain valves handle the supply side, and the section of pipe between the shutoff and the outside device needs its own draining.

Controllers finish the job. Set the system to off or rain mode rather than killing power entirely on units that keep their programming with a battery, and note the spring settings before changing anything. Every spring, landscapers meet owners who protected the pipe and lost the schedule, and now water at noon in July.

Spring startup is part of winterization, not a separate event

A system put to bed correctly announces itself in spring: refill slowly with the backflow valves set properly, run each zone and watch for the geyser that marks a split fitting, check heads that heaved with frost, and confirm the backflow preventer is not weeping at a cracked test cock. Finding one split elbow during a slow April refill is a cheap repair. Finding it after a week of automatic watering is a swamp and a water bill.

Close with the honest division of labor. Blowing out lines is within reach of a careful owner with the right compressor and the discipline to respect the pressure limits. The backflow handling and the spring inspection are where many owners hand it to a pro, not because the steps are secret, but because the part at risk is the priciest one on the system.

Frequently asked questions

Do I really need to blow out my sprinkler system?

In climates with hard freezes, yes. Draining removes water from the main points but leaves it pooled in low sections of lateral lines, valves, and the backflow preventer, and that trapped water is what splits pipe and brass. Mild climates with brief, shallow freezes are the only real exception.

What PSI should I use to blow out irrigation lines?

Keep it modest and matched to the pipe: commonly no more than about 50 PSI for polyethylene and 80 PSI for PVC, with high air volume doing the work. More pressure does not clear lines better. It breaks fittings, damages heads, and can turn a maintenance task into the repair it was meant to prevent.

When should irrigation be winterized?

Before the first hard freeze, which for most cold climate systems means sometime in fall while daytime temperatures are still above freezing to work in. Waiting for a forecast freeze warning compresses every landscaper schedule in town into the same three days, so booking early in autumn is the practical move.

Should I turn the controller completely off for winter?

Set it to off or rain mode rather than cutting power entirely, unless the manufacturer says otherwise. Many controllers hold programming with power or a backup battery, and keeping the unit powered avoids a full reprogram in spring. Note your zone runtimes before winter either way.