Home Postcode finder SA Second Valley Second Valley postcode SA Second Valley is a locality in South Australia covered by postcode 5204. Postcode 5204 State or territory South Australia (SA) Region Adelaide Add a free Second Valley business listing Be the first listing in Second Valley Common questionsWhat is the postcode for Second Valley?Second Valley, SA has the postcode 5204.What state is Second Valley in?Second Valley is in South Australia (SA).Does postcode 5204 cover more than one suburb?Yes. Postcode 5204 covers 10 localities, so the postcode alone does not identify Second Valley. Browse other postcodes in South Australia, or widen the search to every Australian postcode.