Sprinkler Blowout and Backflow Testing in Denver, CO
Irrigation still charged with October approaching? Front Range frost reaches deep enough to freeze water left in irrigation lines and backflow assemblies, and a cracked backflow device costs several times what the blowout would have.
Quick answer
When should sprinklers be blown out in Denver?
Denver sprinkler systems should be blown out between late September and mid October, before the first sustained hard freeze. Front Range frost penetrates deep enough to freeze water remaining in lateral lines, valves, and the backflow assembly, and the backflow device is the most expensive component to replace.
Updated August 2026 by Colton Brackett, Lead Plumber
What this work actually covers
An irrigation system holds water in places that do not drain on their own. Lateral lines run at shallow depth, valve bodies retain water in their chambers, and the backflow preventer above ground holds water in a body made of brass or bronze that cracks rather than flexes when ice forms in it.
Compressed air blowout pushes that water out through the heads, zone by zone. It is not complicated work, but it is done wrong often enough to matter. Too much pressure damages fittings and heads. Too little leaves water behind, which defeats the purpose entirely.
Backflow testing is a separate requirement that runs on its own schedule. The assembly exists to prevent irrigation water siphoning back into the drinking supply, and it is a device with moving parts that needs periodic verification rather than assumption.
The detail that matters
What actually goes wrong, and why here
The backflow preventer is the component worth understanding, because it is both the most expensive part of the system and the one with a public health function. It sits between the potable supply and the irrigation lines and prevents water flowing backward into the house supply, which matters because irrigation water sits in soil among fertiliser and whatever else is on the lawn.
Because it is above ground and made of cast brass or bronze, it is also the component most vulnerable to freezing. Water trapped inside expands as ice, and the body cracks. Replacement is substantially more expensive than the annual blowout that prevents it, which is the whole economic argument for autumn service.
Blowout technique matters more than people assume. Air is introduced after the water supply is isolated, and each zone is opened in turn so air travels the full length of that lateral and exits through the heads. Working zone by zone at moderate pressure clears the system. Pushing high pressure through everything at once damages heads and can blow fittings apart underground, which produces a repair bill in spring rather than preventing one.
What you get
What changes after the visit
Freeze damage is prevented rather than repaired
A blowout costs a fraction of a cracked backflow assembly.
Correct pressure protects the system
Blowing out at appropriate pressure clears water without damaging heads and fittings.
Every zone is cleared individually
Zone by zone work is what actually empties the system rather than the nearest lines.
Backflow function is verified
Testing confirms the assembly protects the drinking supply as intended.
Spring startup finds problems early
Charging the system under observation catches damage before a month of wasted water.
What seasonal irrigation service covers
- Autumn: water supply isolated at the irrigation shutoff
- Compressed air introduced at appropriate working pressure
- Each zone opened in turn until the heads run dry
- Backflow assembly drained and test cocks left open
- Controller shut down or set to the off position
- Spring: system recharged slowly under observation
- Backflow assembly tested and results documented
- Heads checked for freeze damage and coverage verified
Warning signs
Signs the problem is already under way
The system was never blown out last autumn
Freeze damage may already exist and will show at spring startup.
A backflow assembly with visible cracking
Ice damage to the body, which is a replacement rather than a repair.
Water weeping from the backflow after shutoff
Internal seals not holding, which the test is designed to detect.
Heads that stopped popping up after winter
Cracked laterals or damaged heads from ice expansion.
Low pressure across several zones in spring
A split lateral losing water underground before it reaches the heads.
No record of backflow testing
Assemblies need periodic verification, and undocumented ones are simply unknown.
Forecast turning cold with the system still charged?
The backflow assembly freezes first and costs the most to replace. The blowout is a fraction of that.
Call (720) 698-9746Brands We Service
- Rheem
- A.O. Smith
- Bradford White
- Navien
- Rinnai
- Weil-McLain
- Burnham
- Moen
- Kohler
- Zoeller
How long the work takes
A blowout on a typical residential system of six to ten zones generally takes forty five minutes to an hour and a half. Larger systems with many zones take longer because each is cleared in turn.
Backflow testing is a shorter, separate procedure. Spring startup takes similar time to a blowout because the system is charged slowly and each zone is observed running.
What happens after you call
The supply is isolated at the irrigation shutoff
Separating irrigation from the house supply is the first step in either direction.
Air is introduced at working pressure
Appropriate pressure clears water without stressing heads and fittings.
Zones are cleared one at a time
Each lateral is run until the heads discharge air rather than water.
The backflow assembly is drained
Test cocks are opened so no water remains anywhere in the body.
Findings are reported
Any damage or component concerns are documented rather than mentioned in passing.
Denver rules and local conditions that apply
Backflow preventers protect the potable supply from irrigation water and are subject to testing requirements. Assemblies serving commercial properties carry stricter obligations than residential ones.
Front Range frost depth is why autumn blowout is standard practice here rather than optional. The above ground backflow assembly is the component that freezes first and costs the most to replace.
Handling it yourself against calling us
| Factor | Doing it yourself | Calling us |
|---|---|---|
| Autumn shutdown | Turning off the controller and leaving the water in | Lines and backflow cleared with compressed air, zone by zone |
| Pressure | High pressure through the whole system at once | Moderate pressure, one zone at a time, until heads run dry |
| Backflow assembly | Left charged over winter | Drained with test cocks open so nothing can freeze inside |
| Spring startup | Turning it on and walking away | Charged slowly under observation so damage shows immediately |
| Testing | Assuming the assembly still works | Tested and the result documented |
Budgeting
What moves the price up or down
Number of zones
More zones mean more time, since each is cleared individually.
Blowout against testing
They are different services and are frequently scheduled at opposite ends of the season.
System size and layout
Long laterals and distant zones take longer to clear fully.
Whether damage is found
Repairs to cracked laterals or heads are quoted separately from the service.
Timing in the season
Late season scheduling is busier, and booking early is generally easier and calmer.
Sprinkler Blowout and Backflow Testing coverage by ZIP code
Why this crew
Why homeowners call us back
One point of accountability
The technician who diagnoses the problem stands behind the repair.
Built for Front Range conditions
Hard water, expansive clay, and a deep frost line shape every recommendation.
Priced before work starts
Written figures, no hourly surprises, and a straight answer on the cheaper path.
Old systems taken seriously
Prewar boilers, cast iron stacks, and clay laterals get repaired where repair is honest.
Common questions
Questions we field on this work
Between late September and mid October, before the first sustained hard freeze. Booking early avoids the rush when the forecast turns.
A shop compressor rarely delivers the volume needed to clear laterals properly, and too much pressure damages heads and fittings.
Water freezes in laterals, valves, and the backflow assembly. The backflow device is the expensive one, and it cracks rather than flexes.
Periodically, and commercial properties carry stricter requirements than residential ones. Keeping a record matters.
Not on most layouts. Laterals run level or dip, and valve bodies hold water regardless of grade.
Yes, and charging it slowly under observation is how freeze damage gets found in April rather than after a month of wasted water.
It is replaced rather than repaired. Cast brass and bronze bodies do not take a patch.
Access to the shutoff, the backflow assembly, and the controller is needed, though many customers arrange access rather than attending.
Yes. Drip lines and their filters hold water and freeze in the same way, and they are cleared as part of the work.
Book the blowout before the first hard freeze
Zone by zone clearing, the backflow drained properly, and damage reported.