Closing pipes

As you know by previous posts, I am creating pipes with BRepOffsetAPI_ThruSections function.

MakePipe and MakePipeShell are easy to use but I didn't get it what I wanted.

So, ThruSections gives me the desired functionality, but I cannot get a good result in two situations:

1.- Crossing pipes: like 'alpha' letter.
Ok, I will have to notify user not to do that. It has no sense.
2.- Closed pipes: like a '0'. It is almost similar than the previous one, because the pipe is colliding with itself, but this is necessary for me to be able to design it.

So, do you know a way to get it? It is created to be used as a cut boolean shape, so the problem raises when artifacts are created in the final body.

Thanks!