Water expands when it freezes. That is the whole reason this job exists. A sprinkler line left full through a Puget Sound cold snap can split underground, and you will not know until you turn the water on in April and watch a patch of lawn turn into a spring.
Winterization is the visit that empties everything before that can happen.
What the visit covers
- Water shut off at the source and the mainline isolated.
- Every zone blown out with compressed air, one at a time, until the heads run dry. Gravity draining alone leaves water sitting in low spots and inside the heads.
- Backflow assembly drained and insulated. This is the most exposed and most expensive part of the installation, and it sits above ground where the cold reaches it first.
- Controller shut down or set to its off position, so it does not try to run a cycle in January.
- Anything already broken gets flagged with a note, so spring startup is not the first time you hear about it.
Timing
Late October through mid November is the window around here. The trigger is the first hard freeze rather than the calendar, and Puget Sound gives a fairly reliable run of mild autumn weeks before that arrives.
Booking in September is not too early. Booking the week of the first frost warning is late, because every other property owner in the region is calling that same week.
Spring startup
The other half of the job is bringing it back online in spring: charging the line slowly so the surge does not split a fitting, running every zone while somebody watches, and resetting the schedule for spring rather than for August. We cover how that goes in the journal.
Common questions
When should winterization happen?
Before the first hard freeze. Around Puget Sound that usually falls between late October and mid November. Waiting for the first frost warning is leaving it late, because everyone else calls that week too.
Is draining the lines enough?
No. Gravity draining leaves water in low spots and in the heads themselves. Compressed air is what actually clears a line.
What happens if I skip it?
Water expands when it freezes. A split lateral or a cracked backflow assembly is a dig-and-replace job in spring, and it usually costs several times what the winterization would have.