A verifiable mechanical backflow prevention device which will permit water to flow from upstream to downstream but not in the reverse direction.
Maximum permissible fluid category against which a Type EA device is accepted as adequate backflow protection:
Backflow by back pressure: fluid category 2
Backflow by back siphonage: fluid category 2
Interpretation given in Regulators’ Backflow Specification - backflow prevention arrangements and devices: backflow prevention arrangements
