That fill valve uses an easy to replace cap that is what actually shuts the water off. It's a no tools required repair and there's a video on Korky's website and instructions on the cap packaging. Also, when you have the cap off, check the float is properly attached and can move freely. There's a little hole in the float that can get plugged by debris, and it's easy to clean. While you can buy a new valve, it's probably just the cap or the float that needs a little attention. Note, the higher your water pressure, the less time the cap's seal will last. When new, it's a nice dome...as it ages, it gets formed to the shape of the grid above it, and eventually, cracks. Prior to that happening, it tends to have a delay after flushing before it starts to turn the water on to refill, which is a clue that you need to buy a new cap. The cap is about $3 or so, so that it's a lot less than a whole new valve. The rest of it should last a very long time.