I have an American standard toilet that water is running on even after it is full.I am trying to replace / or adjust the assembly (ballcock?) that control the incomming water. I have replace washer in other toilets (Ejer) and you can take apart the assembly and replace only the washers inside it that stop the water. The american stardard is a newer model that I installed a couple of years ago. Is there a way to take the assembly apart or do I have to replace it.