Step 4 · Mark the Drain Pipe Location
The drain pipe (typically a 1 1/2-inch pipe for a bathroom sink) needs to be positioned correctly both vertically and horizontally. Horizontally, the drain should be placed directly on the vanity centerline you just marked. Vertically, consult your vanity's spec sheet for the exact height. If no height is specified, a standard height is between 16 and 20 inches above the FINISHED FLOOR line. Mark the center of the drain pipe opening on the stud at the correct height along your centerline.