I'd like to elliminate the hoses in my vacuflush system in favor of pvc. My question is, can I use standard pcv 90 degree fittings or do I need to find 90 degree sweep fittings that have a more gradual bend?
You want very gradual bends, definitely not 90 degree; that's why top quality hose is preferred. The installation manual for the VF has a little scoring system for things like vertical rises and 90 degree turns that grades an install from bad to ideal. If you don't have one, I think you can get them on line or otherwise order from a dealer. Either way, definitely get the manual.