The mountain irrigation calendar
Colorado high-country irrigation systems run on a tight calendar. Spring startup happens after the last hard frost — typically mid-to-late May in Summit County (8,800–10,500 ft), early-to-mid May in Grand and Eagle County mid-elevations.
Systems run heaviest in July and August when UV is at its peak and ET (evapotranspiration) tops 0.25" per day. Demand drops in September as nights cool. Final blowout happens between late September and mid-October — before the first hard freeze.
Total run window: roughly five months. Inside that window, every detail of system design matters because there isn't time to recover from mistakes.
Design: hydrozones, not 'one schedule fits all'
A well-designed mountain irrigation system zones every area by plant water need — turf on one program, native shrub beds on drip on a different program, hanging baskets and containers on a third. The smartest fixed-schedule timer on the planet can't fix bad zoning.
Drip irrigation is the right choice for trees, shrubs, perennial beds, and any non-turf area. It delivers water directly to the root zone, virtually eliminating evaporation loss, and works perfectly on mountain slopes where spray heads waste water on rocks and hardscape.
Spray and rotor heads still make sense for actual turf areas. Look for pressure-regulated heads with matched-precipitation nozzles — they distribute water evenly across the zone, which means you can run shorter cycles and avoid runoff.
Smart controllers cut water use 30–50%
Weather-based smart controllers (Hunter Hydrawise, Rain Bird ESP-TM2 with LNK Wi-Fi, Rachio) pull local weather data and adjust runtimes daily based on actual conditions. After a rain event, they skip cycles. In a heat wave, they extend them.
Compared to a fixed-schedule timer, smart controllers typically cut water use 30–50% with zero impact on plant health. Many municipalities offer rebates that cover most of the controller cost.
We install smart controllers on every new system and recommend them as a low-cost retrofit on older fixed-timer systems in Summit, Grand, and Eagle County.
Backflow: code, not optional
Colorado plumbing code requires a tested backflow preventer on every irrigation system that connects to a potable water supply. This prevents irrigation water — which has been sitting in pipes and possibly in contact with fertilizer or pesticides — from siphoning back into the drinking water supply.
Backflow assemblies need annual testing by a certified tester. We handle installation, testing, and the paperwork as part of every new system.
Fall blowout: the most important service all year
Water left in irrigation pipes through a Colorado mountain winter freezes, expands, and cracks valves, fittings, backflows, and PVC. Spring repair bills routinely run $500–$2,000 after a missed blowout.
A proper blowout uses a high-CFM compressor (typically 185 CFM or larger for a residential system) to push compressed air through every zone until no water comes out of the heads. Done right, it takes 30–60 minutes per zone.
Don't try to DIY a blowout with a small shop compressor — they don't move enough air to fully clear lateral lines, and water left in low spots still freezes.
