Some good examples of residential plumbing layout include the ones posted on eDrawSoft.com and DawgDrafting.com. Both of these websites lets builders view the examples at no cost, as of 2016.
On the eDrawSoft.com website, there are four types of plumbing plans. There is a directory of common symbols used on each plumbing plan. This website offers software for homeowners and builders to easily draw plumbing plans.
DawgDrafting.com offers links to three different PDF examples of plumbing plans that builders can download and print. There are also 3D drawings of plumbing plans. These are sophisticated blueprints of an entire floor of the home rather than just a single bathroom.