Sprinkler Winterization & Blowout in Northern Colorado: When to Book (NoCo Guide)

Why sprinkler winterization matters in NoCo

Northern Colorado winters are hard on irrigation systems. We routinely drop below 0°F, and a single cold night is enough to freeze water sitting in poly lines, the backflow preventer, and the valve manifold. Water expands roughly 9% when it freezes, and that expansion will split PVC, crack copper, and blow out the brass body on a backflow device.

Replacing a cracked manifold or backflow runs $250-$600+ in our area. A professional blowout is a fraction of that, takes under an hour, and is the single highest-ROI piece of fall maintenance a homeowner can book. Skipping it once is the most expensive way to save $100.

NoCo frost dates (so you know when to book)

These are the long-term averages, not guarantees — NoCo can drop into the low 20s any time after mid-September. Use them as your "book by" deadline, not a safe-to-wait date.

• Loveland, Berthoud, Longmont, Mead, Frederick, Firestone: average first hard freeze around October 5-10
• Johnstown, Milliken, Greeley, Evans, Windsor, Severance, Eaton, Ault: average first hard freeze around October 15-20
• Fort Collins, Timnath: average first hard freeze around October 17-22

When to book the blowout

For most NoCo homeowners, the sweet spot is late September through mid-October. We do them earlier (late August) when people want, but waiting until your system has actually shut off for the season is the more typical flow:

• Stop routine watering once nights start dipping into the high 30s (usually late September in NoCo).
• Run one or two final manual cycles so the lawn and soil moisture are even.
• Book the blowout the same week you do the last watering.
• Don't wait for a hard freeze "warning" — by then the early-October calendar is usually booked solid.

Real talk: late-October calls are the ones we get from people who tried to wait one more week. By then we're stacking appointments and either can't fit them in, or we're doing the job in a cold drizzle. Booking in September is calmer, cheaper, and safer.

What a proper blowout actually does

A real winterization isn't just "open a valve and let it drain." It uses a high-CFM air compressor regulated to the right pressure for your system (poly vs. PVC), run zone by zone, until each head pops clean and the lines are empty. A few things to expect:

• Each zone is blown out individually, not all at once.
• Pressure is regulated — usually 50-80 psi for poly, lower for older PVC.
• The backflow preventer is drained and the test cocks are left open for winter.
• The controller is shut off or set to "rain mode" (we don't usually winterize the controller itself unless it's a non-freeze-rated model).

If your last blowout left you with sticking valves or misty heads in the spring, it was probably under-pressured or rushed. A clean blowout pops every head crisply and leaves the lines dry enough to survive a hard winter.

Can I do it myself?

You can rent a compressor and try — and a lot of NoCo homeowners do. A few things to know before you go that route:

• Most home compressors (the 6-8 gallon pancake or hot-dog styles) don't push enough CFM to clear the lines. You end up under-pressuring the system, which leaves water in low spots that freeze anyway.
• Too much pressure is the other risk. Over ~80 psi on poly lines and you can blow a fitting, pop a solenoid, or split a lateral. We've repaired more than a few DIY mishaps in April.
• The backflow preventer is the expensive part. If you crack it, the city will require a certified test before turning the water back on in spring.

For the cost of a half-day compressor rental and a regulator, most homeowners find it easier to book the service. We bring a commercial rig and it's done in 20-40 minutes per zone.

Worth fixing at the same time

Fall is a great time to knock out small repairs — water is mostly off, parts are stocked, and a winter of freeze-thaw will turn a small leak into a big one. A few quick wins:

• Sunken or tilted heads: raise and level before the ground freezes.
• Sticky valves: if a zone won't shut off cleanly, rebuild or replace the solenoid before the blowout so the system seats properly.
• Cracked laterals or leaking fittings: cheap to fix now, expensive after a freeze.
• Backflow insulation: a $10-15 foam cover from any irrigation supply goes a long way in NoCo. We can install one during the visit.

What to skip in fall

• Don't run the system after the blowout — even a manual cycle will refill lines that were just emptied.
• Don't leave the backflow test cocks closed over winter. They should be open and angled down.
• Don't bury or cover the backflow with dirt or mulch (it traps moisture and can hide a slow leak until spring).
• Don't blow out the system yourself with an unregulated compressor and hope for the best.

How to book (and what to ask)

• Confirm how many zones you have (count the valves, not the heads — easier to over-count).
• Ask whether the backflow is included. Most NoCo pros include it; some charge a small add-on for double-check or PVB styles.
• Ask if small repairs (head replacement, valve rebuild) can be tacked on the same visit. Fall is the best time to do them.
• Ask whether the company documents the winterization — useful if you have a warranty claim in spring.

Related guides: June lawn & sprinkler checkup • Brown spots — mowing vs. irrigation • Summer watering tips • Grub control timing

Serving Northern Colorado: Johnstown, Berthoud, Loveland, Fort Collins, Windsor, Milliken, Timnath, Severance, Mead, Longmont, Greeley, Evans, Firestone, Frederick, Eaton, and Ault.