Every spring we repair sprinkler systems that lost the same gamble: one more warm October week, then a hard freeze nobody watched for. Water left in pipes, valves and the backflow preventer expands as it freezes, and brass and PVC both lose. A single cracked backflow assembly often costs more to replace than a decade of blowouts. Here is how to get the timing right and what proper winterization actually involves.
When to Schedule Your Blowout
On the Salt Lake Valley floor, the first hard freeze — the kind that gets into shallow pipes, not just frost on the windshield — typically arrives in mid to late October. Bench neighborhoods run colder: in Cottonwood Heights and along the East Bench, plan on a week or two earlier. The practical window is late September through mid-October, and the logic is simple: by early fall the state’s Weekly Lawn Watering Guide is recommending one watering a week or none, so the lawn no longer needs the system by the time the freeze risk is real. Book ahead rather than watching the forecast — blowout schedules fill fast once the first cold snap makes the news. And if a surprise freeze beats you to it, don’t panic: one cold night rarely ruptures buried lines. Insulate the backflow preventer overnight with a towel and a bucket over the top, then get the blowout done on the next mild day.
Why Draining Alone Isn’t Enough
Opening the manual drains helps, but it never empties the system. Water sits in low spots along the laterals, inside valves and heads, and — most expensively — inside the backflow preventer, whose brass body is usually the first casualty of a hard freeze because it sits above ground. Our slow-draining clay soil also keeps the trench backfill around pipes wet, so frost reaches them faster than people expect. Only compressed air actually clears the lines.
What a Proper Winterization Includes
- Shutting off the irrigation supply at the stop-and-waste valve and letting the main line drain.
- Blowing out each zone one at a time with a high-volume compressor at safe pressure — around 50 psi for most residential heads — until the heads run mist, not water.
- Draining the backflow preventer and leaving its ball valves and test cocks open at 45 degrees so trapped water has room to expand.
- Setting the controller to off or rain mode so a warm spell doesn’t trigger a watering cycle into a charged line.
- Noting any broken or tilted heads found along the way, so spring repairs are a quick list instead of a surprise.
Can You Do It Yourself?
The honest answer: the shut-off and controller steps, yes; the blowout, usually not. Small pancake compressors can hit 50 psi but can’t deliver the air volume needed to push water out of a full zone, so lines look clear while low spots stay wet. Running zones on air too long, or too hot, also melts gear drives inside rotor heads. Given that a professional blowout costs a small fraction of even a minor freeze repair — and typical sprinkler repairs here run well into the hundreds — it is one of the cheapest insurance policies in home ownership.
A Note for Spring
Startup matters too. Open the stop-and-waste valve slowly so a wall of pressurized water doesn’t slam closed valves, then walk every zone looking for geysers, tilted heads and dry spots before the summer watering season begins. If something did crack over winter, this is when it shows itself.
Hernandez Landscaping runs sprinkler blowout routes through East Salt Lake City and Cottonwood Heights every October, often paired with fall cleanup visits so the whole yard gets put to bed in one stop. If you want on the list — or you suspect last winter left you a leak — estimates are free.
