This 3D model is of a Screw Cap designed for a 20l container. The model is designed to house a rechargeable water pump. It can be 3D printed with no supports if placed on the side, or if preferred, one may place a small support in the middle while it's standing upright, depending on individual bridging capabilities.

Pump used can be found here.

I have also included the parasolid file if anybody wishes to make changes.