Every spring, we get the same call from homeowners in Palatine and Arlington Heights: the irrigation system was fine in October, and now zone three is a geyser in the front lawn. Almost every one of those calls traces back to water that was left in the system over the winter. Chicagoland frost depth runs 36 to 42 inches in a hard winter, and irrigation piping sits far shallower than that. Water expands roughly 9% when it freezes, and that expansion has to go somewhere — usually through a fitting, a valve body, or the brass guts of your backflow preventer.
This guide covers what winterization actually involves, what it costs, what freeze damage looks like when it happens anyway, and how the backflow rules in northwest suburban Cook County affect you.
Why Blowing Out an Irrigation System Isn’t Optional Here
Some regions can get away with draining a system by gravity. Northern Illinois is not one of them. Lateral lines are typically installed with minimal slope, heads hold water in their bodies, and valve manifolds trap water no matter how the yard grades. The only reliable method is a compressed-air blowout, zone by zone.
The parts that fail first, in the order we see them:
- Backflow preventer — brass body, thin walls, sits above grade. The single most expensive freeze casualty.
- Valve manifold solenoids and bodies — plastic cracks at the seam, usually not visible until the system is pressurized in April.
- Sprinkler head bodies — cheap individually, but a freeze event rarely takes just one.
- Poly lateral lines — split lengthwise, requiring excavation to locate and repair.
When to Winterize in Palatine & Arlington Heights
The safe window is roughly October 1 through November 1. The first freeze in the northwest suburbs averages mid-October, but we have seen hard freezes in the last days of September. If you wait for a forecast to scare you into it, you are competing with every other homeowner in the village for the same handful of appointments.
A practical rule: schedule your blowout the same week you schedule your furnace tune-up. Both belong to the same seasonal checklist, and pairing them saves a trip charge.
What a Professional Winterization Includes
1. Shut down and isolate the supply
The interior irrigation shut-off is closed and the system is isolated from the house plumbing. If your shut-off is seized — common on systems older than 15 years — it gets flagged before it becomes a January emergency.
2. Compressed-air blowout, zone by zone
Air is introduced downstream of the backflow device at controlled pressure: 50 PSI or less for poly pipe, 80 PSI or less for PVC. Each zone is run until the heads spray mist rather than water, then a second pass is made. High-volume, low-pressure air is what matters here; a small pancake compressor from a hardware store cannot move enough CFM to clear a lateral, which is why most DIY blowouts leave water behind.
3. Backflow preventer protection
Test cocks are opened to a 45-degree angle, ball valves are left half-open, and on RPZ assemblies the device is drained fully. Many homeowners skip this step and lose a $400 to $900 assembly.
4. Controller shutdown
The timer is set to “rain mode” or off, and the backup battery is checked so your programming survives to spring.
Cost Ranges: Winterization and Common Repairs
| Service | Typical Cost | Notes |
|---|---|---|
| Winterization blowout (up to 6 zones) | $90 – $150 | Add $10–$20 per additional zone |
| Spring startup & head adjustment | $95 – $175 | Includes leak check and programming |
| Backflow preventer test (annual) | $75 – $125 | Required by many local water departments |
| Backflow preventer replacement | $450 – $1,200 | PVB vs. RPZ, size dependent |
| Sprinkler head replacement | $12 – $35 each installed | Rotor heads cost more than spray heads |
| Valve/solenoid replacement | $120 – $300 per valve | Manifold access affects labor |
| Lateral line repair (located & excavated) | $250 – $700 | Depends on run length and landscaping |
| Full freeze-damage restoration | $900 – $2,500 | Multiple zones, manifold, backflow |
Prices reflect typical northwest suburban jobs and vary with system size and access. We quote in writing before work starts, and larger repairs can be spread out with Sunbit or PowerPay financing.
Backflow Prevention: The Rule Most Homeowners Miss
Illinois plumbing code requires that any irrigation system connected to a potable water supply be protected by an approved backflow prevention assembly. Many Cook and Lake County water departments — including several villages in our service area — require an annual test by a licensed cross-connection control device inspector and send notices to homeowners who fall behind.
Two things trip people up. First, the test is not the same as the winterization; it is a separate certified procedure with a filed report. Second, a device that froze last winter will often still hold water pressure but fail the test, because the internal check assemblies are cracked. If you have received a notice from your village, handle it before the reinspection deadline — fines and shut-off notices are real.
Signs Your System Took Freeze Damage
- A zone that will not build pressure, or heads that barely pop up
- Water pooling around the valve box or backflow assembly when the system runs
- A soggy strip of lawn that stays wet between watering cycles
- Water hammer or banging when a zone shuts off
- Visible cracks or a bulge in the brass backflow body
- A jump in your water bill with no change in habits
Do not keep running a system with a suspected lateral break. A split line under pressure can move a surprising amount of soil, and in homes with below-grade foundations the water tends to find the footing drain — and then the basement.
Can You Winterize It Yourself?
You can shut off the supply, set the controller to off, and open the backflow test cocks. Those steps are genuinely DIY. The blowout itself is where homeowners get into trouble: too much pressure shatters fittings and destroys head seals, too little leaves water in the lines, and an unregulated shop compressor can do both in the same afternoon. The equipment rental plus the risk usually costs more than the service call.
Frequently Asked Questions
How late is too late to winterize?
Once you have had two or three consecutive nights below 28°F, damage may already be done. Winterize anyway — it prevents further damage — but expect a spring pressure test to check for cracks.
Do I need to winterize if my system was “drained” by the installer?
Manual and auto-drain valves help, but they do not clear heads, valve bodies, or low spots. Blowouts remain the standard in Illinois.
Does homeowners insurance cover freeze damage to irrigation?
Typically no for the buried system itself. Resulting water damage inside the home may be covered depending on your policy. Check with your carrier.
How long does a winterization take?
Most residential systems take 30 to 45 minutes. Larger properties with 10 or more zones can run an hour or more.
My backflow preventer is dripping. Is that an emergency?
A relief-port drip on an RPZ means an internal check has failed. It is not a burst-pipe emergency, but it is a code violation and it will get worse. Have it evaluated promptly.
Schedule Your Winterization Before the Calendar Fills
MMDS handles irrigation winterization, spring startups, backflow testing coordination, and freeze-damage repair across Palatine, Arlington Heights, and the surrounding northwest suburbs — along with full plumbing services, drain cleaning, and seasonal HVAC maintenance. One call covers the whole seasonal checklist.
Call (847) 221-6280 or request an appointment online. Ask about Sunbit and PowerPay financing on larger repairs.