Object of below level visible in upper level

[ax80]

Hi all,
I'm trying to understand what's wrong with my object height, as some objects (pipelines set just below ceiling of lower level) are visible in upper level, at least in the design mode (I mean, not in 3D mode).

My measures are the following:
- below level: elevation 0m thickness 0,12m height 3,02m
- upper level: elevation 3,31m thickness 0,29m height 3,02m
- cube (pipeline): elevation 3m height 0,02

I noticed that if I change elevation of upper level to almost 3,61m, the pipelines are not visible nor in 3D (as of before) nor in design mode, but then the measures are not the correct ones.

Just a side comment, in order to represent pipelines that come from below level to upper level, I added additional "vertical" pipelines close to one set at ceiling level that should in that case be visible in the upper level, my intention was to see only those ones.
Thanks for help!!!