Connection between filtering cap and container

A filtering assembly comprising:

• a container having a connection end on an end thereof and a flange extending spirally from an outside of the connection end, the flange having a positioning portion which is the longest section of the flange, a first inlet and a first outlet defined through the connection end and two seal rings mounted to two respective outsides of the first inlet and the first outlet, a wave-shaped ring located at an end surface of the container and the connection end extending from the end surface;
• and
• a filtering cap having a second inlet and a second outlet defined in an outside thereof, the second inlet and the second outlet located communicating with the first inlet and the first outlet respectively, an inner skirt and an outer skirt located in the filtering cap, the inner skirt having a groove defined in an inside of the inner skirt and the flange engaged with the groove, the groove having a positioning port which is the deepest portion of the whole groove, a plurality of bosses extending from an inside of the outer skirt, the positioning portion being engaged with the positioning port and the bosses engaged with the wave-shaped ring when the filtering cap is located onto the container.