Step 4 · Locate and Mark the Drain Line
This is a critical step. First, determine the drain's horizontal position. For a standard vanity, the sink drain is usually aligned with the main vanity centerline you already marked. Verify this with your spec sheet. Next, determine the vertical height. The goal is to position the drain stub-out from the wall so that a standard P-trap can be installed correctly. A common standard height for the center of the drain pipe is 18 to 20 inches from the finished floor. However, check your vanity's internal structure. If there is a drawer or shelf, you must position the drain stub-out to avoid it. The spec sheet may indicate a specific drain location. Mark the intersection of the drain's horizontal centerline and its vertical height. This 'X' is the target for the center of your drain pipe.