Author: Dianne DeLongchamps
When should I winterize (blow out) my sprinkler system in Fort Collins, Windsor or Timnath?
Get your sprinkler system blown out before the first hard freeze, not on a fixed date every year. Watch the extended forecast for a real cold snap, with several nights in a row well below freezing, instead of circling one date on the calendar. This applies in Fort Collins, Windsor, and Timnath alike, because the date shifts every year.
Luke DeLongchamps, who runs the field side of our business, says shutting the sprinkler system off too early is the most common mistake he sees. In his experience, a system can survive a light freeze, and September into October is an important recovery period for grass, so he does not rush it. Our own sprinkler shutoffs normally begin in October, once nights start freezing. If you would like us to look at your system, Clean Air Lawn Care serves Fort Collins, Windsor, and Timnath.
Why a fixed date doesn’t work
The Colorado Climate Center’s review of fall freeze data found that first-freeze timing lines up pretty well with elevation: higher ground freezes earlier, and lower elevations freeze later. Along the Front Range and the eastern plains, that first freeze has generally shifted one to two weeks later since 1980. That’s a real change. A date that worked for your parents’ generation might now run a week or two early. Tracking the ten-day forecast is the safer approach.
What water left in the pipes actually does
CSU Extension’s guide to preparing a sprinkler system for winter says water expands by one-eleventh of its volume when it freezes. That is nearly a tenth, and the guide says the force is enough to burst pipes and fittings and to split open sprinkler and pump cases. It lists pipes, fittings, valves, sprinklers, and pumps as the parts that freezing water will break. The guide frames the work as preparing the system in the fall. That fits Luke’s timing, where the shutoff comes after the grass has had its September and October recovery and before the hard freeze arrives.
Why compressed air, not drain valves
The same guide calls compressed air the only positive way to be sure enough water has been expelled. It also says not to trust manual or automatic drain valves, and it says systems with electric valves must be blown out with pressurized air.
Getting the pressure right
The guide keeps the compressed-air pressure in a 40 to 80 psi range overall, but caps it by pipe type: up to 80 psi for rigid PVC, and no more than 50 psi for flexible polyethylene. Its rule of thumb for compressor size is to divide your system’s zone GPM by 7.5 to get the compressor’s required CFM. The guide says to take the zone’s GPM from your irrigation plan, or to add up the GPM ratings of each nozzle on that zone. If the sprinkler heads stay popped up and air keeps flowing through the system once the water is out, the compressor is the right size for the job.
The backflow preventer needs its own handling
This is the part that trips up DIY attempts. CSU’s guide says pressure vacuum breaker devices should not be blown out with compressed air at all. Instead, its ball valves and test cocks get exercised several times, then left in a half-open position for the winter, and closed again before spring pressurization. A reduced-pressure device is handled differently: its two check-valve zones get drained separately, through their own test cocks and check cap, with the isolation ball valves left partway open for winter. The guide’s steps for that device start with slowly closing the main shutoff valve upstream, and they leave the isolation ball valves at roughly 45 degrees over winter. In spring, it says to open the ball valves slowly, because that prevents damage from water hammer. Getting this piece wrong is one of the more expensive mistakes a homeowner can make trying to save money on a professional visit.
Signals worth watching, not a date on the wall
- The extended forecast shows several nights in a row with lows in the mid-20s or lower
- Most trees nearby have dropped the bulk of their leaves
- You’ve already had your last fall feeding treatment
- You’re heading into the final couple weeks of October along the Front Range, in a typical year
What happens if you wait too long
Fall prep is far less costly and far less work than the spring repairs that follow a hard freeze hitting a system that never got winterized. A cracked backflow preventer or a split mainline fitting often isn’t found until the system gets turned back on in spring, sometimes as a flooded patch in the yard.
We’d rather tell you to get it scheduled a little early than have you guess at it yourself, and we’re glad to get you on the calendar.
Clean Air Lawn Care Northern Colorado is owned by Dianne, Paul, and Luke DeLongchamps — a family business serving Fort Collins, Windsor, and Timnath with organic lawn treatments and solar-powered electric equipment.
