This guide teaches you how to replace a toilet flapper and detect when you have a leaking toilet flapper. Its primary job is to create a watertight seal, preventing water from leaking into the toilet bowl when the tank is full Before you go out and buy a replacement toilet flapper, find out how to clean the flapper or adjust the chain to ensure it seals properly.
How-to: Fix a Running or Leaking Toilet - Flapper Replacement - YouTube
If your toilet keeps running, you may have a leaky toilet flapper
Fluidmaster show you how to fix this problem.
The flush valve seal, also known as the flapper, is a rubber or silicone component that sits at the bottom of the flush valve