toilet overflow leaking?

For a start your in the wrong section unless you clean your teeth in the cistern.
At the water inlet end the pin on the end of the arm presses on a pin sticking out of the inlet valve so shutting of the water. If the pin on the arm [you can't ben these arms] should have a lock nut this may be loose. turn the pin in towards the pin in the valve until the water stop flowing at the correct level then hold the pin [should have screwdriver slot on the end and tighten the lock nut to stop the pin moving. If it still runs in then you need a new washer in the valve. turn off the water Undo the large nut on the valve where the pin is sticking out. pull out the pin/plunger and washer, large disc washer on most, obtain new washer refit and it should be ok.

Bob
September 2010