The activation of a residential irrigation system in Colorado presents a unique seasonal dilemma due to the state’s volatile spring climate. Unpredictable temperature swings and late-season freezes pose a significant threat to the system’s integrity after it has been winterized and drained. Rushing to turn on the sprinklers too early risks expensive damage from water freezing and expanding within the pipes and components. Therefore, the timing of the spring startup must be carefully determined by environmental factors rather than a fixed calendar date.
Determining the Ideal Start Window
The most reliable indicator for safely starting your irrigation system is the consistent absence of freezing temperatures. Homeowners should wait for the period when the risk of a hard freeze, which can damage a pressurized system, has substantially diminished. For much of the Front Range, this window generally falls between mid-April and mid-May, but the specific date is dictated by meteorology.
The most commonly cited guideline is to wait until after the average last freeze, which Denver Water suggests is typically around May 5th. More precisely, the system should not be pressurized until nighttime temperatures are reliably staying above 32°F. Even one night below freezing can cause water to expand and crack pipes or, more commonly, damage the backflow prevention device.
The moisture content of the soil also provides a clue that the system is not yet needed. Colorado’s spring snow and rain often supply enough moisture to sustain the lawn until warmer weather arrives. If you can easily insert a screwdriver a few inches into the turf, the soil is adequately hydrated. Consider hand-watering any dry patches until the weather stabilizes.
The Process of Safely Activating Your System
The physical process of bringing your system online must prioritize slow pressurization to prevent a damaging phenomenon known as water hammer. Begin by ensuring the main water supply valve to the irrigation system, often located in the basement or utility room, is fully closed. Next, confirm that the valves on the exterior backflow prevention device (BFP) are in the off position before proceeding.
You should then slowly open the main interior water supply valve only about one-quarter of the way to allow water to trickle into the mainline. This gradual flow is essential for removing air pockets and slowly building pressure without straining the components. Once a trickle of water begins to flow into the BFP, you can slowly open the isolation valves on the backflow device itself. These valves must be opened one at a time to avoid a sudden surge that can instantly damage the internal components.
After the main line is fully pressurized, turn the system controller to the manual setting and run each zone for about two minutes. This step allows you to walk the property, inspect each sprinkler head for leaks, and ensure all lines are clear and functioning correctly before setting the seasonal watering schedule.
Understanding Colorado Water Restrictions and Schedules
Even after a system is safely activated, the use of sprinklers across Colorado is governed by local municipal water conservation rules. These regulations are designed to manage water use in a semi-arid climate and typically apply from May 1st through October 1st. A common rule is the restriction of watering between 10 a.m. and 6 p.m. to minimize water loss from evaporation during the hottest part of the day.
Most communities limit irrigation to a maximum of three days per week; some, like Denver Water, recommend only two days a week for established lawns. The specificity of the rules varies significantly by water provider and geography. Cities such as Brighton or Broomfield often enforce mandatory assigned watering days based on a property’s address number.
Compliance with these schedules is mandatory, and local water authorities enforce them through fines for non-compliance. During periods of prolonged dryness, many municipalities will enact formal “drought stages” which impose stricter limits, such as reducing watering to only one or two days per week. Residents must check with their local water provider to understand the exact days, times, and volume restrictions in effect for their area.