Home Postcodes by state WA 6122 Postcode 6122 6122 is the postcode for 4 localities in WA: Byford, Cardup, Darling Downs and Karrakup. Localities with postcode 6122ByfordWACardupWADarling DownsWAKarrakupWA Postcode 6122 State or territory Western Australia (WA) Localities 4 Council area Serpentine-Jarrahdale Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 6121 · Postcode 6123