An underwater storage system collects waste, measures the collection and stores the waste in underwater storage tanks from whence the material is pumped when inlet measurement indicates the necessity. Automatic systems are provided for the storage of sewage waste during peak periods and in large flexible walled tanks having flat rectangular bottoms with horizontal oriented inlet and outlet means. When the peak systems are passed, the present invention provides automatic means to reintroduce the stored sewage into the sewage treatment system. The automatic waste, collection, storage and emptying systems and the flexible containers used in those systems have particularly useful application to sewage systems.