What should be clearly marked on the plumbing drawing to indicate the direction of true north?

The north arrow is a critical component of plumbing drawings as it provides a clear indication of the direction of true north. By marking true north on the drawing, it helps to orient the various elements of the plumbing system in relation to the overall site plan. This orientation is essential for ensuring that installations and connections align correctly with other structures and systems, as well as adhering to any local codes or standards that might dictate the orientation of fixtures and piping.

Having a north arrow also assists in understanding the layout in relation to the surrounding environment, including utility lines, drainage systems, and other site considerations. It ensures that the plumbing installation is designed with the appropriate context in mind, making it easier for plumbers, builders, and inspectors to visualize how the project fits within the overall site.

While scales, reference points, and site lines serve important purposes in the drawing—such as providing dimensions, indicating specific locations, or helping visualize boundaries—they do not convey the directional orientation necessary for a full understanding of the plumbing layout in relation to the larger site context. Therefore, the inclusion of a north arrow is vital for accurately interpreting the drawing.