COMPRESS provides option to attach nozzles to other nozzles. But COMPRESS is limited to the number/types of components that can be attached to the end of the nozzle: the nozzle (in shell) cannot be extended with elbow, piping, etc (only heads and flanges can be attached to the end of the nozzle).
If you have the case where the nozzle projects vertically from the bottom head, then has an elbow and horizontal piping, with the 4" drain in the horizontal run, you can model the horizontal pipe as a cylindrical shell in a second COMPRESS vessel file and attach the 4" nozzle.
Tom Barsh
Codeware Technical Support