Clean the Flush Valve Seat - How to Replace a Toilet Flapper to Fix a Running or Weak Flushing Toilet

Step 3 · Clean the Flush Valve Seat

With the old flapper removed, carefully inspect the flush valve seat, which is the circular rim that the flapper seals against. It must be perfectly smooth to prevent leaks. Use a non-abrasive sponge or cloth to thoroughly wipe down the entire surface of the valve seat, removing any grime, mineral deposits, or leftover rubber residue.