Sprinkler winterization checklist: the zone-by-zone blowout, step by step

Updated 2026-10-08

Short answer: shut the water off, connect the compressor downstream of the backflow assembly with the compressor valve closed, close the assembly's isolation valves, then blow out one zone at a time starting with the farthest or highest, about two minutes each or until no water leaves the heads. Stop when a zone is dry. The steps below follow a published trade-press procedure, with the places where sources disagree flagged.

Before you connect

Confirm the compressor. A trade-press guide says to use 80 to 100 CFM for a mainline 2 inches in diameter or smaller. A small shop compressor will not move enough air.
Set the regulator below the weakest part of the zone. That guide says keep pressure below the maximum operating pressure of the lowest-rated component in the zone and never exceed 80 psi. Other guides are more conservative: a consumer guide we read says not to exceed 50 psi. Where sources disagree, take the lower number unless the manufacturer's specs for the heads and pipe in front of you allow more.
Eye protection on, and do not stand over components. Heads and debris can fly.

The blowout, zone by zone

Turn off the irrigation water supply.
With the compressor valve closed, attach the hose to the mainline after the backflow device, using a quick coupler, hose bib or similar connection. Connect after the device, not to it.
Close the backflow isolation valves before you open the compressor valve. Frozen water in the assembly can damage its internal parts and crack the brass body.
Activate the controller station farthest from the compressor, or the one with the highest heads.
Slowly open the compressor valve. Run the zone for about two minutes or until no water leaves the heads.
Work through the remaining zones one at a time, finishing with the one closest to the compressor.
Do not keep blowing air through a zone once it is dry.
Shut off and disconnect the compressor and open its valves to release leftover pressure.

The tedious part people skip: the record

The blowout is only half the job. The other half is being able to answer in April: was this system blown out, by whom, on what date, and what did they see?

Date, technician and the controller or system serviced.
Zones cleared, and any zone that still pushed water after the usual time.
The compressor pressure setting you used.
Anything seen: a cracked head, a leaking valve, a backflow assembly that was already damaged. Photograph it and note which zone.
Whether the customer's annual backflow test is still due (see how to track backflow test due dates).

The faster way, honestly scoped

Sprinklerly keeps the irrigation system as a record (controller, zones, components), moves each visit through a logged work order from confirmed to completed with every status change recorded, and can assign more than one technician with one designated crew lead. A finding logged against a zone comes back flagged if a component there is still under warranty. Sprinklerly does not ship a built-in winterization checklist template, so the checklist above stays your own SOP. Sprinklerly is free during early access for contractors who sign up by December 31, 2026 (no credit card). Planned prices at general availability are $79, $149 and $249 per month, locked in for early-access accounts.

Start free Free during early access for sign-ups by December 31, 2026, no credit card required.

Common questions

What PSI should I use to blow out sprinklers?

Sources differ. A trade-press guide says keep pressure below the maximum operating pressure of the lowest-rated component in the zone and never exceed 80 psi; a consumer guide says not to exceed 50 psi. Use the lower figure unless the manufacturer specs for that zone allow more.

Which zone do you blow out first?

The zone farthest from the compressor, or the one with the highest heads, and finish with the zone closest to the compressor.

Sources

Landscape Management: step-by-step winterization of an irrigation system, read 2026-10-08
A consumer winterization guide recommending a lower 50 psi ceiling, read 2026-10-08

Sprinklerly is not affiliated with, endorsed by, or sponsored by any utility, agency, manufacturer or publisher linked on this page. Names are used only to identify the sources. Rules for backflow testing, licensing and insurance differ by state, utility and customer, so confirm with your own authority; this page is practical guidance, not legal advice. The Sprinklerly features described are those currently shipped in the product.