Step 2 · Remove the Old Toilet Fill Valve

This is the step people usually slow down on. Go finger-tight first, then a quarter turn. No rush — replay the clip whenever it helps.

Carefully disconnect the water supply line from the old fill valve. Then, use an adjustable wrench or pliers to unscrew the lock nut securing the fill valve to the tank. Once the nut is loose, gently remove the old fill valve. Inspect it to better understand the cause of the problem (if you can).