Major plumbing problems have to be addressed by professionals but there are minor troubles, like adjusting a ballcock on the toilet, which can be done by the homeowner. If you have ever flushed the toilet and the water continued to run, then you have a problem with the height of the ballcock assembly in the tank. There are two issues that can cause the water to continue to run. The first is that the water is too high, so the float ball does not properly close the valve, allowing water to enter the overflow tube. The second issue is that the float ball is broken, which lets water in and subsequently doesn’t allow the valve to close properly. Here's how to adjust the ballcock for either type of situation.
Step 1 - Prepare
In order to work with the toilet, and specifically the ballcock, you need to turn the water off. Look behind the tank of the toilet. You will see a shutoff valve to just that individual toilet. The valve should be near the floor and is usually found on the left side of the toilet. Turn the valve clockwise in order to turn the water off.
Remove the cover to the toilet tank. You will see a few simple things like a float ball, lever, and gaskets. Do not concern yourself with these things yet, as for now you need to empty the tank. In order to do this all you have to do is push down on the flusher. The water will exit through the gasket at the bottom of the tank and not refill, because you turned the water off.
Step 2 - Locate the Ballcock
Now that the tank is empty you can begin to identify the pieces inside the tank. You will see a float ball that is attached to a metal or plastic rod. These two things are attached to another lever, which is attached to the flush lever. When you flush the toilet the lever lifts and the float ball rises. When this happens a chain is pulled, which pulls up a diaphragm that is covering the hole to the pipe. For this easy fix, you should only concern yourself with the thumb screws near the top of the assembly. They may be screws or wing nuts.
Step 3 - Adjust the Ballcock
The moisture in the tank can cause issues with adjusting the ballcock. Dry the assembly with the towel and then grease the screw area with a small amount of the petroleum jelly. This will help to lubricate the screw so that it can be easily moved. In order to lower the ball further to close off the pipe, turn the screw clockwise by half turns. This will drop the float ball more precisely than bending the lever. Then test the system to ensure it if functioning properly.