Step 2 · Gain Access to Faucet Plumbing
Locate the plumbing access panel. This is usually a square piece of wallboard on the wall behind the faucet handles, often inside an adjacent bedroom or linen closet. These panels may be held in place with four screws or simply be a friction-fit panel that can be pried off. Use a screwdriver to remove the screws, if present, and carefully take the panel off. If no panel exists, you must create one by using a utility knife or drywall saw to cut a hole (typically 12x12 inches) in the drywall. Put on your headlamp to get a clear view of the plumbing connections.