Toilets are a useful modern convenience when they are functioning properly, but can be irritating when they have problems. Understanding how the toilet works will make it much easier to treat if and when problems develop. The problem with a toilet in constant operation or leaks is usually related to the float valve. Only old toilets have float valves; these have been replaced in the new toilets with discharge valves.
Kohler K-4067-NY Bancroft Comfort Height Elongated Bowl, Dune
Tilted arm float valve
If the toilet is running constantly, either, or stops before the bowl has been filled, the problem may be that the arm of your float valve is bent, causing the float valve to be at the wrong height. Remove the lid of the toilet tank from your rear and take a look. The plastic or metal ball that floats on the surface of the water is the float valve. When the water rises high enough, the ball is pushed upwards and a shut-off valve is activated. If the arm bends up, the water will reach high enough to start running the overflow before closing the valve. If the arm bends down, the valve will close before the bowl has finished filling.
Waterlog
Sometimes, the float valve can develop a crack or leak, causing it to fill with water. When this happens, it no longer floats on the surface of the water. When the chain is pulled, the rear tank will refill, but the ball will not float on the surface of the water, and the water will simply continue to run in the rear tank and exit through the overflow valve.
Break
If the arm of the float valve is bent or shaken too badly, the float valve may break out of it. If you take the lid of your rear tank and you see the float valve floating in the water, but not connected to anything, this is obviously what happened. You will probably need to replace both the float and the float arm to operate the toilet correctly.