Complete Backflow Preventer Winterization Guide for Idaho Homeowners
Published: October 25, 2024 | By: Lawn Care Kuna Team | Category: Irrigation
Tags: backflow preventer, winterization, sprinkler blowout, freeze protection, irrigation maintenance, winter preparation
Why Backflow Preventer Winterization Matters
Your irrigation system's backflow preventer is both a critical safety device and one of the most freeze-vulnerable components in your sprinkler system. Located above ground and exposed to Idaho's harsh winter temperatures, backflow preventers can suffer severe freeze damage that results in costly repairs or replacement. For Treasure Valley homeowners, proper winterization of this essential device is just as important as blowing out sprinkler lines—and often overlooked until expensive damage occurs.
Understanding what your backflow preventer does, why it's vulnerable to freezing, and how to properly winterize it protects your investment and ensures your irrigation system is ready when spring arrives. This guide covers everything Idaho homeowners need to know about protecting their backflow devices from winter damage.
Understanding Your Backflow Preventer
What Is a Backflow Preventer?
A backflow preventer is a required safety device that prevents irrigation water (which may contain fertilizers, pesticides, or other contaminants) from flowing backward into your drinking water supply. When pressure drops occur in the municipal water system—from water main breaks, fire hydrant use, or other events—backflow preventers stop potentially contaminated irrigation water from being sucked back into the potable water system.
Common Backflow Preventer Types
Several types of backflow preventers are used in residential irrigation:
| Type | Installation | Freeze Vulnerability |
|---|---|---|
| Pressure Vacuum Breaker (PVB) | Above ground, 12"+ above highest head | High—fully exposed |
| Reduced Pressure (RP) | Above ground | High—fully exposed |
| Double Check Valve (DC) | Can be below ground | Lower if properly buried |
| Spill-Resistant PVB (SVB) | Above ground, 12"+ above highest head | High—fully exposed |
In the Treasure Valley, Pressure Vacuum Breakers (PVB) and Reduced Pressure (RP) assemblies are most common for residential irrigation. Both require above-ground installation, making them vulnerable to freezing.
Why Backflow Preventers Freeze
Several factors make backflow preventers particularly vulnerable to freeze damage:
- Above-ground location: Required for proper function but exposes devices to cold air
- Metal and brass components: Conduct cold efficiently
- Internal water retention: Valves and chambers hold water that can freeze
- Complex internals: Springs, seats, and check valves are easily damaged by ice expansion
- Height above ground: Often in exposed locations away from building heat
Freeze Damage: What Happens and What It Costs
Types of Freeze Damage
When water inside a backflow preventer freezes, expanding ice damages internal and external components:
- Cracked body: The bronze or brass housing cracks from ice expansion. Requires complete replacement.
- Damaged check valves: Internal check valve assemblies are forced out of position or broken. May be repairable.
- Broken relief valve: RP devices have relief valves that freeze and break first. Component replacement possible.
- Damaged springs and seats: Precision components are distorted by ice. Rebuilding required.
- Test cock damage: Small valves for testing crack or break off. Can be replaced.
Repair Costs
Freeze damage repair costs range widely based on damage extent:
- Minor damage (test cock replacement, minor parts): $50-150
- Moderate damage (rebuild with new internals): $150-300
- Major damage (complete device replacement): $300-800+
- Emergency repair (after burst during freeze): $500-1,200+
Compare these costs to proper winterization—typically included in sprinkler blowout service or $20-50 if done separately. Prevention is dramatically less expensive than repair.
Winterization Procedures
When to Winterize
In the Treasure Valley, backflow preventer winterization should occur:
- Before nighttime temperatures consistently drop below 32°F
- Typically late October to early November
- In conjunction with sprinkler system blowout
- Before any hard freeze forecast, even if earlier than typical
Step-by-Step Winterization Process
Step 1: Shut Off Water Supply
Locate and close the shutoff valve that supplies water to your irrigation system. This is typically found in your basement, crawl space, or near your water meter. Turn the valve completely closed.
Step 2: Release System Pressure
Open the backflow preventer test cocks slightly (turn handles to 45-degree angle). This relieves trapped pressure in the system. You may hear air escape or see a small amount of water drain.
Step 3: Drain the Backflow Preventer
With test cocks open and water supply off:
- Open both shutoff valves on the backflow device (handles perpendicular to pipe)
- Allow water to drain from the test cocks and relief valve
- Leave valves partially open to prevent trapping water
Step 4: Blow Out Remaining Water
During professional sprinkler blowout, compressed air passes through the backflow preventer, removing most remaining water. If doing this yourself:
- Connect compressor to blow-out fitting downstream of backflow device
- Use regulated pressure (40-80 PSI, never exceed rated pressure)
- Air moves through the device, pushing water out through upstream side
- Repeat until no water appears
Step 5: Position Valves for Winter
After draining and blowing out:
- Main shutoff valves: partially open (45-degree angle)
- Test cocks: open at 45-degree angle
- Ball valves: partially open to prevent trapped water
This positioning prevents water from being trapped while allowing any condensation to drain.
Insulation (Supplemental Protection)
While proper drainage is the primary protection, insulation provides additional freeze resistance:
- Insulated covers: Commercial covers designed for backflow preventers provide some protection
- Foam insulation: Can be wrapped around device (remove in spring)
- Insulated boxes: Permanent or removable enclosures with insulation
- Heat tape: Electric heat tape provides active freeze protection (requires power)
Important: Insulation alone does not replace proper drainage. Insulation slows freezing but doesn't prevent it during extended cold periods. Always drain devices properly regardless of insulation.
Common Winterization Mistakes
Incomplete Drainage
The most common mistake is leaving water trapped in the device. Check that:
- All test cocks are open at 45 degrees
- Main valves are positioned to drain, not seal
- Relief valve (on RP devices) has drained
- No water remains in low points
Relying Only on Insulation
Insulation alone doesn't prevent freeze damage. It only delays freezing. A properly insulated but water-filled device will still freeze during extended cold periods. Always drain first, then add insulation as supplemental protection.
Forgetting Downstream Components
The backflow preventer isn't the only above-ground vulnerable component. Don't forget:
- Exposed pipe between shutoff and backflow device
- Pipe from backflow device to where it enters ground
- Any exposed valves or fittings
Late Winterization
Waiting until after the first hard freeze risks damage. Idaho weather can shift suddenly from mild to severely cold. Schedule winterization for late October or early November regardless of current temperatures.
Spring Reactivation
Inspection Before Use
When spring arrives, inspect your backflow preventer before turning on water:
- Check for visible cracks or damage
- Ensure all test cocks and valves are intact
- Look for corrosion or deterioration
- Verify all handles move freely
Reactivation Procedure
Proper spring startup protects against damage:
- Close test cocks completely
- Slowly open upstream shutoff valve (fill gradually to prevent water hammer)
- Check for leaks at all connections
- Open downstream shutoff valve
- Operate relief valve to verify function (RP devices)
- Run irrigation briefly to verify operation
Annual Testing Requirements
Most Idaho jurisdictions require annual backflow preventer testing by certified testers. Schedule testing after spring reactivation:
- Verifies proper function after winter storage
- Identifies developing problems before they worsen
- Meets legal requirements for potable water protection
- Documents compliance for water utility records
When to Call Professionals
Professional Winterization Benefits
Professional sprinkler winterization includes complete backflow preventer protection:
- Proper drainage techniques for your specific device type
- Compressed air blowout to remove trapped water
- Correct valve positioning for winter
- Inspection for pre-existing damage or wear
- Identification of potential problems
Signs of Freeze Damage
Contact a professional if you notice after winter:
- Water leaking from the device when system is off
- Visible cracks in bronze or brass body
- Missing or broken test cock handles
- Relief valve continuously discharging (RP devices)
- Unable to pass annual backflow test
Repair vs. Replacement Decisions
Our irrigation repair team can evaluate damaged backflow preventers and recommend repair or replacement based on:
- Extent of damage
- Device age and overall condition
- Availability of replacement parts
- Cost comparison of repair vs. replacement
- Code requirements for your jurisdiction
Protect Your Investment
Your backflow preventer is a required safety device that protects drinking water quality. It's also a significant investment that proper winterization protects for years of service. Taking time to properly drain and position your device before winter—or having professionals do it as part of comprehensive system winterization—prevents costly freeze damage and ensures your irrigation system is ready for spring.
Lawn Care Kuna provides complete sprinkler winterization services throughout Kuna, Meridian, Boise, Eagle, Star, and the Treasure Valley. Our winterization includes proper backflow preventer protection along with complete system blowout. Request a free quote for winterization service, or contact us to schedule before freezing temperatures arrive.
Frequently Asked Questions
Can I winterize my backflow preventer without a professional blowout?
You can perform basic winterization yourself, though professional blowout provides more complete protection. DIY winterization involves: shutting off water supply to the irrigation system, opening test cocks to 45-degree angle, positioning shutoff valves partially open to allow drainage, and optionally adding insulation. This removes most water through gravity drainage. However, water can remain trapped in internal chambers that only compressed air effectively removes. If you don't have professional blowout, at minimum ensure complete drainage and add insulated cover for additional protection. Properties with history of freeze damage, expensive devices, or complex systems benefit most from professional service that guarantees thorough water removal.
What temperature will damage my backflow preventer?
Water freezes at 32°F, but freeze damage typically occurs when temperatures drop significantly below freezing for extended periods. Brief dips to 30-32°F usually don't cause damage, especially if the device retains heat from prior warm conditions. However, extended exposure below 28°F creates serious risk, and temperatures in the teens or lower almost certainly cause damage to water-filled devices. In the Treasure Valley, overnight temperatures regularly drop into the 20s and teens from November through February, with occasional periods in single digits or below zero. Any device with trapped water faces freeze damage during these conditions. Don't wait for hard freezes—winterize when overnight temperatures begin consistently approaching freezing.
Do insulated backflow preventer covers provide adequate freeze protection?
Insulated covers provide supplemental protection but do not replace proper drainage. Covers slow heat loss, giving devices more time before reaching freezing temperatures. During brief cold snaps, covers may provide adequate protection. However, during extended freezing periods (several days of below-freezing temperatures), covers only delay the inevitable—a water-filled device will eventually freeze regardless of insulation. Think of covers as additional protection after proper winterization, not as standalone freeze prevention. The most effective approach combines complete drainage, proper valve positioning, and insulated covering. Some homeowners also use heat tape (electric heating cable) with insulated covers for active freeze prevention, though this requires power supply and increases costs.
My backflow preventer is leaking after winter—is it freeze damage?
Post-winter leaking often indicates freeze damage, though other causes are possible. Common freeze damage symptoms include: water continuously running from relief valve (RP devices), leaks from cracked body or fittings, test cocks that won't close properly, and water spraying from unexpected locations. However, leaking can also result from normal wear, sediment accumulation, or failed seals unrelated to freezing. Have a professional evaluate the device to determine whether damage is freeze-related. If the device was properly winterized and still leaks, freeze damage is less likely and other causes should be investigated. If the device was not winterized or was improperly drained, freeze damage is the probable cause. Document the damage for potential insurance claims if applicable.
How do I know if my backflow preventer is properly drained for winter?
Properly drained backflow preventers have specific characteristics: all test cocks are positioned at 45-degree angles (partially open), shutoff valves are positioned partially open rather than fully open or closed, no water drips or runs from any opening when pressure is released, and relief valves (on RP devices) show no water discharge. After draining, you can verify by opening a test cock fully—only air should escape, not water. If water continues dripping for more than a few seconds, the device isn't fully drained. Professional blowout uses compressed air to force remaining water out of internal chambers that gravity drainage can't reach. If you've drained but aren't confident it's complete, professional blowout provides certainty and is worthwhile insurance against expensive freeze damage.
Is backflow preventer winterization included in sprinkler blowout service?
Most professional sprinkler blowout services include backflow preventer winterization as a standard component—the compressed air used to blow out sprinkler lines typically passes through the backflow device, removing trapped water. However, confirm this with your service provider. Complete backflow winterization should include: shutting off water supply, blowing compressed air through the device, positioning all valves and test cocks correctly for winter, and inspecting for damage or wear. Some services offer enhanced protection like installing insulated covers. When scheduling blowout service, specifically ask whether backflow preventer winterization is included and what the process involves. Lawn Care Kuna's winterization service includes complete backflow preventer protection as part of comprehensive system winterization.