3 D website for imaging a storage unit made of pipe?

Factual Questions
1

I’m building a storage unit. The framing will be made of heavy duty (schedule 80) PVC pipe. In order to know exactly how many pipes and the kinds of fittings I’ll need, I’d like to made a 3 D model of it.

Are there any good 3 D sites that allow one to use pipes and pipe fittings as a building material for structures?

2

I haven’t used that particular extension, but some Googling suggests that Google Sketch Up has this feature available.