I didn't notice any back flow preventors in the catalogs... are there any out there? it also seems that there is very little in the plumbing fittings other than the very standard fittings like elbows and tees... I'm not missing something am i? Even ball valves seem to come only as larger steel threaded types rather than smaller copper soldered pipe style... is that right? I don't mind drawing the parts... but I just don't want to create parts that already exist but that i was just too dumb to find.