How to Draw Isometric Pipe & Fittings Schematics


Learning how to draw a plumbing system is very useful if you want to add a fixture to your current system. Plumbing schematics are done as an isometric drawing, which is a 3-D view of pipes, drainage and vent lines. An isometric drawing might be required for a building permit and will demonstrate to the code inspector that your system either meets the minimum standards or needs to be adjusted to meet standards.

  • Visualize the inside walls of a room in which the pipes are located to understand an isometric sketch of a piping system. The isometric sketch should be reduced to the pipe diagram itself (drainage and vent lines) and not other fixtures such as the bathroom sink or tub.

  • Create a drawing that looks three-dimensional by drawing the lines that represent each pipe at certain angles. To obtain the proper perspective look at your plumbing system from above, bird's eye view and at an angle instead of eye level or looking up.

  • Draw dashed lines to represent vent pipes and solid lines for pipes that carry water. Show how and where the new vent pipe connects to an existing vent pipes or exits the roof as a new separate vent. .

  • Call out the size and direction changes of each pipe shown on your plumbing schematics by drawing a line from the pipe and adding the pipe size or direction at the end of the line.

Tips & Warnings

  • Check with your city code office to be sure you are allowed to create your own isometric drawing.
  • Using a drafting 30-60-90 plastic triangle will make drawing angles easier. Code requires a 30-degree slope that represents pipes running horizontally.

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  • Photo Credit pipe fitting image by Joann Cooper from
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