Type CA – Non-verifiable disconnector with different pressure zones

A non-verifiable mechanical backflow prevention device which provides disconnection by venting the intermediate pressure zone of the device to the atmosphere when the difference of pressure between the intermediate zone and the upstream zone is not greater than 10% of the upstream pressure. 

Maximum permissible fluid category against which a Type CA device is accepted as adequate backflow protection:

Backflow by back pressure: fluid category 3

Backflow by back siphonage: fluid category 3

Note: relief ports from Type CA backflow prevention devices shall terminate with an air gap, the dimension of which should satisfy a Type AA air gap. 

Interpretation given in Regulators’ Backflow Specification - backflow prevention arrangements and devices: backflow prevention arrangements