Professional plumbers usually map a job in painstaking detail to prevent surprises. You should too. Even with a plan changes may be necessary as you work. The framing you find in a wall may be different than you expected or there may be wiring where you want to run pipes.
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 when drawing a plan to indicate the function of each pipe.
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.
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.