Question: Is my toilet running? How can I tell if my toilet is running?
Answer: If you notice water flowing continuously from your toilet soon after you flush, and maybe even nonstop, this is an indication that there is a leak in your tank.
What You Can Do
First, inspect the flapper, it is the rubber or plastic valve at the edge of the tank. Make sure it closes completely when you're not flushing, as this might be the leak source.
Try to adjust the flow inside the toilet tank if the toilet still flows after inspecting the flapper valve and the loop. The float is spherical and at the end of metal rod. The float adjustment controls the amount of water within the tank. Make sure the overflow pipe lies within an inch of the base.
If these suggestions do not fix the issue, you may have a leaky or brittle fill valve that trickles water into the tank. This is a fairly basic fix, although before replacing the fill valve you will have to shut down the water to that toilet.
Is high water pressure causing my toilet to run? Find out if high water pressure the problem here.