Type LA – Pressurised air inlet valve

An anti-vacuum valve or vacuum breaker, similar to Type DA but suitable for conditions where the water pressure at the outlet of the device under normal conditions of use is greater than atmospheric. 

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

Backflow by back pressure:  not acceptable for protection against back pressure from any fluid category

Backflow by back siphonage: fluid category 2

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