The valve for a toilet is located by the floor on the left side of the toilet. It supplies water to the toilet through the toilet's flush valve. The valve is often referred to as a water stop valve or a shut-off valve. The valve allows the supply of water to the toilet to be discontinued so repairs can be implemented. Sometimes the valve leaks and needs to be repaired. The most common cause for leaks from the valve is a loose retaining nut.
Tighten the nut that secures the water supply hose to the valve. Sometimes this may be the cause of the leak. Hold the valve with a pair of slip-joint pliers and use an adjustable wrench to turn the nut clockwise one-eighth of a turn.
Dry the valve and the water supply hose with a paper towel and watch to see if the leak persists.
Tighten the screw in the centre of the handle for the valve using a screwdriver. Sometimes if the leak is coming from the valve, the cause may be a loose handle.
Grasp the water line with a pair of slip-joint pliers to keep it from twisting. Tighten the retaining nut on the valve with an adjustable wrench. Tighten the nut one-eighth of a turn clockwise and wait to see if the leak persists. If it does, turn it another one-eighth of a turn. Do not overtighten the nut or you could snap off the valve. If the leak does not stop, you may need to consider replacing the valve.