Step 5 · Mark Water Supply Line Locations
The water supply lines (typically 1/2-inch pipes) feed the hot and cold water to the faucet. Standard practice places them a few inches above the drain line and spaced several inches apart. A common layout is: measure 3 inches above your drain centerline mark for the height of the supply lines. Then, measure 4 inches to the left of the main vanity centerline for the hot water line, and 4 inches to the right for the cold water line. This creates an 8-inch spread between them. Mark these two locations clearly. 'Hot on the left, cold on the right' is the universal standard.