Your PVC plumbing diagram may need more symbols than found elsewhere on this site, so here's a chart of standard symbols accepted and used by people in the trade. The particular drawing or diagram you're making most likely will require less than a dozen symbols, but for accuracy, if you choose, you may find icons you'll need if you're also creating a floor plan of the area.
The following chart (courtesy Purdue University - College of Technology) applies to copper, metal and PVC plumbing diagrams, floor plans and other building and remodeling purposes.
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