If the toilet does not have a shut-off valve on its water supply line coming out of the wall or floor, then you will have to shut off the main shut-off valve for your house. (However, you really don't have to shut the water off to a toilet unless you're changing the toilet tank water valve or the toilet itself.)
You may only need a new flapper, which is usually the case when a toilet won't stop running. Get a new flapper. If there are two small L-shaped brackets at the base of the overflow pipe in the middle of your tank, cut the 0-ring out of the new flapper and hook the two little flapper "ears" onto those brackets. Adjust the flapper chain to where it just has enough slack to allow the flapper to seat fully when the handle is released.
Also, if your toilet tank has a float ball on a brass rod, you may be able to stop it from running by bending the brass rod by hand to lower the ball. To see if this will work, simply raise the float ball to see if that shuts off the water running into the tank. If so, bend the rod. You don't need to shut the water off for that, either.
If that doesn't do it and you have a float-cup type toilet water valve, you may need to replace either the flapper or the toilet tank water valve or both to stop it from leaking and running all of the time.
Get a Fluidmaster 400A float-cup type toilet tank water valve and a flapper. Just follow the easy, illustrated directions that come with it.
Toilet tank parts are very inexpensive and easy to change.
Last edited by Mike Swearingen; 12-17-2007 at 06:28 AM.