Backflow Preventer Calculator
Determine the correct backflow prevention device based on hazard level, pipe size, and application type.
Results
Visualization
How It Works
Backflow preventers protect the potable water supply from contamination caused by back-siphonage or backpressure. The device type depends on the hazard level — higher hazard requires more protection.
The Formula
Selection based on hazard level and application:
Low hazard → AVB or PVB
Medium hazard → PVB or DCVA
High hazard → RPBA (RPZ)
Fire → DCDA
Low hazard → AVB or PVB
Medium hazard → PVB or DCVA
High hazard → RPBA (RPZ)
Fire → DCDA
Variables
- AVB — Atmospheric Vacuum Breaker — simplest, no backpressure protection
- PVB — Pressure Vacuum Breaker — protects against back-siphonage
- DCVA — Double Check Valve Assembly — moderate hazard protection
- RPBA — Reduced Pressure Backflow Assembly — highest residential protection
Worked Example
Irrigation with fertilizer (medium hazard), 1" pipe: Use PVB. Cost $150-500 + $250 install. Annual test ~$75.
Practical Tips
- Most jurisdictions require annual certified testing of testable devices
- RPBAs discharge water when they detect backflow — install where drainage is available
- Hose bib vacuum breakers are cheap insurance ($8-15 each)
- Check local plumbing code — some areas require RPBA for all irrigation