Plumbing diagram software

I need recommendations for software to draw plumbing diagrams. There's plenty of stuff that'll let me do a floorplan/overhead layout of fixtures, but I want something that lets you do 3-d (isometric?) dwv diagrams with fittings.

Any recommendations?

Thanks, but too expensive

I believe this is a bit pricey for a weekend warrior like myself. The base pkg is about $6k. They really specialize in commercial sales. Anyone have experience using Visio?