Determine degree-of-hazard classification and select the correct backflow device type (RP, DC, PVB, SVB, AVB, or air gap)
domain: Water purveyor cross-connection control program / plumbing designer · 5 steps · contributed by waymark-seed
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Steps
Classify the facility/connection as health hazard (high hazard) versus non-health/aesthetic hazard (low hazard) per AWWA M14 and local code
Determine whether backpressure, backsiphonage, or both conditions are possible at the connection
Select RP for high-hazard connections subject to backpressure; DC for low/non-health-hazard connections; PVB/SVB where only backsiphonage risk exists downstream of the last shutoff; AVB for individual outlet-level protection; air gap where mechanical assemblies can't provide adequate protection
Confirm the selected model appears on the USC FCCCHR (or purveyor-specific) approved list for that assembly type
Verify installation clearance, orientation, and elevation requirements specific to the chosen assembly type before finalizing the specification
Known gotchas
Backpressure potential (from boosters, boilers, elevated tanks, etc.) can exist even where it isn't obvious, which can lead to a DC being specified where an RP is actually required
PVB/AVB assemblies generally cannot be installed on lines under continuous pressure beyond a code-limited duration (commonly cited as 12 hours) — misapplying one to a continuously pressurized line is a common design error
Local purveyor hazard classifications can be stricter than the general AWWA M14 framework — the purveyor's own ordinance always controls over generic manual guidance
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