When Should You Blow Out Sprinklers in Denver? A Fall Guide for Property Managers

A warm afternoon can make it feel like there is plenty of time left. Then a cold front arrives overnight. For Denver landlords and property managers, sprinkler winterization belongs on the early fall work order list, alongside furnace checks and exterior water shutoffs.

When is the right time in Denver?

Start scheduling in September and aim to have each system shut off, drained, and professionally blown out before the first hard cold snap. Denver Water advises turning off and draining sprinkler systems before the first freeze. The National Weather Service lists October 7 as Denver’s average first freeze date, but that is an average, not a deadline: Denver has recorded first freezes in September. Watch the forecast for the specific property, especially exposed backflow devices and aboveground piping.

What happens if sprinklers stay on too long?

Water left in lines, valves, sprinkler heads, and backflow equipment can freeze and expand. That may crack parts above or below ground. A leak can remain hidden until spring startup, when it becomes a soggy patch, a pressure problem, a water bill surprise, or a visible spray. Running an irrigation schedule into freezing weather can also leave icy walks and entry paths. Waiting for snow to appear is too late to manage that risk.

What a complete fall visit should cover

Confirm the correct irrigation shutoff and system type; shut off the irrigation water; drain and blow out the zones using equipment and pressure appropriate for the system; protect the backflow assembly according to its design; turn off watering schedules; and document completion by property and date. Do not blow compressed air through a backflow device. Colorado State University Extension recommends proper downstream fittings and short cycles so heat and pressure do not damage components. If a component is already leaking or frozen, have the system assessed rather than forcing it to run.

FAQ: Denver sprinkler blowouts

1. Is October 7 the last safe date?

No. It is the historical average first freeze at Denver’s official climate station. Individual neighborhoods and seasons vary, so finish before a forecast freeze at your property.

2. Can I just turn the controller off?

No. A disabled schedule prevents watering, but water can remain trapped in piping and backflow equipment. The system still needs the proper drain or blowout procedure.

3. Should a property manager wait until the grass turns brown?

No. Lawn appearance does not predict the first freeze. Schedule based on forecast risk and the system’s exposure.

4. What if a freeze is forecast before our appointment?

Contact your irrigation professional promptly about the correct temporary shutoff and drain steps for that installation. Keep people clear of wet walkways, and do not operate a frozen system.

5. Can a sprinkler system be damaged underground?

Yes. Denver Water notes that freeze and thaw cycles can create underground cracks and weak spots that show up later as silent leaks.

6. Does winterization mean the landscape never needs water again?

No. Colorado’s dry winters can call for occasional hand watering of trees and shrubs on suitable above-freezing days, even while the irrigation system remains winterized.

Put the work order on the calendar

Blueprint Turnkey helps coordinate access, irrigation work, completion photos, and follow-up notes across Denver Metro rental properties. Call or text 720-573-1756, email workorders@blueprintturnkey.com, or fill out the service-request form at https://www.blueprintturnkey.com/.

Sources

Denver Water, Cold Weather Tips: https://www.denverwater.org/residential/services-and-information/troubleshooting-and-repairs/cold-weather-tips

National Weather Service, Denver Fall/Winter/Spring Statistics: https://www.weather.gov/bou/DenverFallWinterStatistics

Colorado State University Extension, Preparing Your Sprinkler System for Winter: https://extension.colostate.edu/resource/home-sprinkler-systems-preparing-your-sprinkler-system-for-winter/