Home Postcode finder WA Old Plains Old Plains postcode WA Old Plains is a locality in Western Australia covered by postcode 6569. Postcode 6569 State or territory Western Australia (WA) Region Wa Subs 4 Coast Add a free Old Plains business listing Be the first listing in Old Plains Common questionsWhat is the postcode for Old Plains?Old Plains, WA has the postcode 6569.What state is Old Plains in?Old Plains is in Western Australia (WA).Does postcode 6569 cover more than one suburb?Yes. Postcode 6569 covers 2 localities, so the postcode alone does not identify Old Plains. Browse other postcodes in Western Australia, or widen the search to every Australian postcode.