Home Postcodes by state WA 6422 Postcode 6422 6422 is the postcode for Walgoolan, WA. Localities with postcode 6422WalgoolanWA Postcode 6422 State or territory Western Australia (WA) Localities 1 Council area Westonia Council area based on Australian Bureau of Statistics data (ASGS Edition 3), CC BY 4.0. Postcode 6421 · Postcode 6423