Cubic modular composite water tanks are made of a large number of prefabricated panels that have been produced by SMC method. For this purpose, first the SMC raw materials, which are placed in the form of sheets in the form of lavashka with a width of approximately one meter in the form of sheets and under a certain pressure in the defined time, are turned into hard panels in the shape of squares or rectangles. They come in different thicknesses. From the production of panels in the press station, in the drilling station, special precision holes are made in the edges of the panels by a special machine, thus it is possible to connect the panels to each other using special screws and sealing tape. By creating a concrete foundation required at the installation and assembly of these parts together can be quickly constructed roofed drinking water tanks with the highest international health standards up to a volume of 20,000 cubic meters.