Some resources for PVC plumbing diagrams include Enviosmau.com and ConceptDraw.com. Both of these websites offer diagrams at no cost, as of 2016. Enviosmau.com offers the most detailed diagrams and additional information.
Enviosmau.com provides multiple diagrams for plumbing including PVC and copper pipes. This website includes detailed instructions on installation of pipes in the home when the homeowner does the work. There are sections on vent plumbing and plumbing for new home constructions. The diagrams offer blue and red lines that identify which are hot and which are cold lines.
ConceptDraw.com offers PVC plumbing diagrams for residential use and some other areas, such as food trucks. This website offers an extensive list of symbols and their meanings.