Step 3 · Clean the Flush Valve Seat
Before installing the new flapper, it is crucial to clean the surface where it will sit. This surface is called the flush valve seat, the smooth, circular rim of the drain opening. Over time, this seat can accumulate mineral deposits, sediment, or bits of deteriorated rubber, which can prevent a perfect seal. Use a cloth or a non-abrasive scrub pad to wipe the rim thoroughly until it is completely smooth and clean to the touch. A clean seat is essential for preventing leaks.