Step 4 · Clean the Drain Opening
With the old flange removed, you'll see a ring of old, hardened plumber's putty. Use a plastic putty knife or the edge of an old credit card to carefully scrape all of this old putty off the surface of the tub around the drain opening. Avoid using metal scrapers which can easily scratch the tub finish. Once the bulk is removed, use a clean rag dampened with denatured alcohol or mineral spirits to wipe away any remaining oily residue. Use a small wire brush to gently clean the threads inside the drain shoe to ensure the new flange can be installed smoothly without cross-threading.