Take a few minutes to figure out why you have a run-on toilet, and then you can repair it. You have a run-on toilet if each flush doesn’t end with a gurgle but instead continues with a hissing sound, with water running into the toilet bowl. To find the source of the trouble, remove the toilet tank top and place it in a safe location. Then push the flush lever and watch what happens. Don’t worry about the water in the toilet tank — it’s clean. Run-on toilets are usually caused by a problem with the tankball, the ballcock or intake valve, or the floatball.