The old, joke, of course, is, if the answer is yes, go catch it.

But running toilets can be annoying, and can cause your water bills to go up.  So here are some tips on what to do if your toilet is running.

  1. First, test to see if the toilet is running.  If the toilet is running slowly, you won’t be able to tell by just looking at it.  Put about 10 drops of food coloring into the tank and wait about 10 minutes.  If the food color shows up in the bowl, the toilet is running.
  2. It may be something as simple as the flapper chain being twisted or snagged (the flapper is the rubber stopper that lifts to release water into the bowl).  This shortens the chain’s length, and prevents the flapper from properly sealing.  So check to make sure that the chain is not snagged, and that there is some slack when the flapper is properly sealed.
  3. If the chain is not the problem, investigate the flapper.  If water is constantly running from the tank into the bowl, the most common cause is a worn flapper.  Flappers do deteriorate over time.  You can try to clean it and see if that works.  If not, you can test the flapper by pushing down on it with a stick and listen for the water to stop.  If it does not, the flapper is not sealing properly and you need a new one.  You can pick up a flapper at most hardware stores (make sure you know the exact type or the toilet may not flush properly).  And make sure you shut off the water before you change it.
  4. If the flapper is not the problem, the problem could be the position of the float.  When a toilet is flushed, the tank should stop filling when the water is just below the overflow pipe.  If the water goes over and the tank is still filling, the float may be too high.  You may be able to adjust the float, lowering the float in the tank.  Just be careful not to break the fill valve.
  5. If none of those are the problem, you may need to replace the fill valve.  This takes a little more work.  You will need to drain the tank.  Then you will need to unscrew the water supply line and lock nut from outside the tank.  If you do not feel confident doing this yourself, call a licensed plumber.