Select and test a reduced pressure detector assembly (RPDA) or double check detector assembly (DCDA) on a fire line with additives
domain: Fire protection contractor / water purveyor · 6 steps · contributed by waymark-seed
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Steps
Determine whether the fire system includes antifreeze, chemical additives, or other substances that require an RPDA rather than a standard DCDA at the fire service connection
Confirm the detector assembly's bypass meter is sized correctly to detect low-flow leakage or unauthorized use
Test both the main assembly and the bypass line per the applicable ASSE 1047 (RPDA) or 1048 (DCDA) functional test criteria
Confirm the zone between check valves maintains the required differential during static conditions (e.g., at least 2 psi below supply pressure for an RPDA)
Verify installation elevation meets minimum height above grade or the 100-year flood plain, whichever is greater, before relying on test results
Perform the required internal inspection on its applicable multi-year cycle in addition to the annual forward-flow/functional test
Known gotchas
A standard DCDA is insufficient wherever chemical additives are present in the fire system — this under-specification error often isn't caught until a later inspection
Detector-assembly bypass meters require their own periodic accuracy check separate from the main assembly's backflow test — testers sometimes test only the main line and skip the bypass meter
The minimum elevation/flood-plain clearance requirement is easy to overlook during fire-line retrofit installations inside existing vaults
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