A Homeowner’s Guide to Protecting Your Irrigation System During Missouri’s Coldest Months
When temperatures drop in Missouri, one of the first irrigation components at risk is your backflow preventer. This device keeps contaminated water from flowing into your home’s clean water supply — and unfortunately, it is also one of the most exposed and freeze-prone parts of your sprinkler system.
A single cold snap can crack the housing, burst internal parts, or cause leaks that lead to costly spring repairs.
The good news: with a few simple steps, you can protect your backflow preventer and avoid expensive freeze damage this winter.
Why Backflow Preventers Freeze So Easily
Backflow assemblies are typically installed above ground, which exposes them directly to freezing air. Even if the rest of the irrigation system is winterized, this component can still hold residual water.
When water freezes, it expands — and that expansion can crack:
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The brass body
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Internal springs
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Poppets and seals
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Test ports
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Pipe fittings
Most homeowners discover the damage in early spring when they turn on their irrigation and notice leaks spraying from the unit.
Step 1: Shut Off the Irrigation Water Supply
Your first line of defense is to ensure the irrigation line feeding the backflow is turned completely off at the main shutoff valve.
If you aren’t sure where this valve is located or whether it’s fully closed, Automatic Rain can verify it during a winterization inspection.
Step 2: Open the Test Cocks to Release Pressure
Once the water supply is off, you should relieve any pressure in the backflow.
This is done by turning the test cocks (small valves on the side of the assembly) to a 45-degree angle.
This prevents trapped water from building pressure as temperatures fluctuate.
Step 3: Insulate the Backflow Preventer
Insulation protects the device from sudden temperature drops. Homeowners can use:
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A fitted backflow insulation bag
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Heavy-duty foam pipe insulation
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Weatherproof backflow covers
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Towels wrapped in plastic for a temporary solution
The goal is to keep cold air from directly contacting the brass body.
Avoid sealing the backflow airtight — it still needs ventilation to prevent moisture buildup.
Step 4: Add a Heat Source During Extreme Temperatures
For extended cold snaps, homeowners can use a low-wattage heat cable or wrap-around heat tape designed for outdoor plumbing.
This is especially useful for older homes or systems with less protected backflow locations.
Never use space heaters or open flames near irrigation components.
Step 5: Check the Backflow After Each Freeze Event
After a heavy freeze, look for early signs of damage such as:
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Dripping or spraying water
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Hairline cracks
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Water pooling around the base
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Hissing or whistling sounds
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Difficulty turning valves
Catching these symptoms early can prevent full system failure when spring arrives.
What to Do if Your Backflow Is Already Frozen
If you notice your backflow has frozen or is leaking:
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Turn off the irrigation water supply immediately.
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Do not try to thaw it with hot water or excessive heat — this can cause more damage.
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Contact a professional to inspect the assembly before the next freeze.
Automatic Rain performs mid-winter repairs, replacements, and inspections to ensure your system is safe for spring.
Why Winter Backflow Protection Matters
A frozen backflow preventer can lead to:
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Hundreds of dollars in repair or replacement costs
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Delayed spring irrigation system activation
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Water waste from leaks
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Contaminated water if the device fails completely
Taking preventative steps now protects your irrigation investment and ensures your system is ready to go when you need it in the spring.
Need Help Protecting Your Backflow This Winter?
Automatic Rain provides:
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Mid-winter freeze inspections
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Backflow insulation and repair
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Emergency winter irrigation services
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Spring start-ups and full system diagnostics
Book your winter inspection or repair today and prevent costly damage before temperatures drop again.