I've been using Revit for WWTF modeling on and off for 2-plus years. There's a few suppliers (valves, for example) who have Revit family libraries (most are either really, really old and/or aren't fully set up for Revit, so some tweaking can be required), and there's more who are making them as time goes on.
Some, you may find, are willing to supply you 3d content of their equipment/accessories if you contact them and ask (I have one supplier who will make me whatever accessory of their's that I request, with a turnaround of a day at most. They're using such requests to build their full library, which they intend to release to the public when it's done)
Also, be prepared to create a decent amount of your own content; nowhere near every supplier is able or willing to provide 3d content.
Keep in mind that 2 1/2 years ago some of the out-of-the-box content for large-diameter piping was dimensionally incorrect as well. I'm not sure if that's still the case or not, but something to keep an eye out for.
edit: P.S. - alot of the equipment I receive from vendors / manufacturers is in a format not native to Revit. It has to be run through other software, like Inventor, to get it into a format that can be brought into Revit.
