The present invention relates to an automatic pneumatic pumping system of the type using two or more pumping tanks which are filled in alternate sequence with liquid from a common source and are alternately purged by for example air pressure or other pumping fluid so as to effect a continuous and uninterrupted flow of the liquid into a discharge line and relates to its revolutionary application to marine vessels, e.g. barges, which carry liquid, slurry and certain dry types of bulk cargo. It should be understood that the term "pneumatic" as herein used includes all types of pumping fluids or gases and not just compressed air and the term "liquid" includes slurries and the like.