Professional plumbers usually map a job in painstaking detail to prevent surprises. You should too. It's fairly easy to produce plan views and riser drawings that use official plumbing symbols.
Making detailed drawings will save time and expense later. Also, drawing the project helps you think through the job in detail, which may enable you to spot something that you might otherwise overlook. It will almost certainly minimize extra trips to the plumbing supply store. A clear, professional-quality plan also will make your initial meeting with the building department more productive.
A plan for new plumbing starts with a map of the existing plumbing. Use color codes and these universally recognized symbols on your drawings to clearly denote each component of your plan.
If you have architectural drawings, make several photocopies of them. Otherwise make several copies of an accurate scale drawing of the room. A gridded straightedge will help you draw parallel lines. You'll also need color pencils, an eraser, and a 30-60-90-degree triangle. Use grid paper and establish a scale, such as 1/2 inch equals 1 foot. Drawing to scale makes it easy to note any problems with the layout. It also helps in estimating materials.
To make a plan drawing, first draw all fixtures to scale size and make sure they are not too close together. Put in the drain lines and vents for the fixtures, then add the supply lines. Make riser drawings to show vertical pipe runs as well.
Indicate pipe sizes and the exact type of every fitting so the inspector can approve them. Indicate locations for valves, including stops at fixtures, and specify the type of valve. Make a shopping list of materials based on the drawings.
It's a good ideas to code your map. Show drainpipes with solid lines and supply lines with broken lines. Indicate vertical runs with notes on the overhead view. Mark hot and cold supply lines with color pencils and color-code drains and vents. Point to pipe sizes with a curved leader line to avoid mistaking the leader for a pipe. You'll probably draw several versions of the plan before you get all the details right.
A drain-waste-vent (DWV) elevation describes the upward path of the stack, vents, and revents; the length of drainpipe runs; and traps. Its primary purpose is to show how the fixtures will be vented. It doesn't have to be drawn over an architectural drawing.
A supply drawing indicates the estimated length of supply pipes. The main purpose is to determine the minimum size of the pipes.