"Interchanging Ideas" is a detailed account of the Victorian Water Industry Engineers and Operators Conference, which began on September 30, 1938, with 37 sewerage engineers and operators. Initiated by Mr. E. A. Hepburn, the Sanitary Engineer of the Commission of Public Health, this first meeting aimed to unite professionals involved in sewerage and sewage treatment. Over the decades, this modest gathering has evolved into three annual state conferences, attracting hundreds of delegates, featuring sold-out trade shows, and hosting national and international speakers. This e-book celebrates the conference's history, acknowledging the contributions of its convening agencies and providing a fascinating read for those interested in the field's development and impact on public health in Victoria.