Normally the tank of a toilet will sit quietly until the lever is pressed, pull the chain, unless there is a problem with one of the various pieces inside the tank. Be careful when removing the reservoir cap, as it can easily break and is not easily replaced. Do not worry about wearing gloves when working with the toilet tank, however, since none of the sewage from the toilet never enters the tank.
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Hinge Valve
A flapper valve on the drain in your toilet tank will allow a drip or more of water to come out of the tank constantly. The dripping of water will eventually reduce the level of water in the tank to the point that the float in the toilet will trigger the filling valve, which will refill the tank to the level you have set. This will continue again and again until the fin valve is replaced with a new one, which costs little and takes only a few minutes to install.
Adjustment of the chain
Your flapper valve may be in perfect condition, but the small chain that connects the valve to the toilet handle can cause the tank to refill without touching the handle. The chain should allow the flap valve to rest completely on the drain at the bottom of the tank, but it should also not have so much slack that the links are attached up. Slide the chain from the clip that attaches to the handle, and try other links until you find the correct setting.
Fill the valve tube
The filling valve inside the toilet tank uses a plastic tube, which sends water through the overflow tube into the toilet. The water that flows down the overflow tube makes its way to the toilet bowl, filling the container at the same time the tank top-ups. The pipe can siphon water out of the tank if the pipe falls down into the actual overflow pipe. Use a clip that holds the tube over the opening of the overflow tube, keeping the tube in the overflow tube.
Float adjustment
Toilet floats either sit on the end of a metal arm, or they slide up and down on a metal rod inside the toilet tank. The float provides feedback to the tank fill valve on the amount of water in the tank. When the water falls below a certain level, and along with it the float, the filling valve will start at and bring the reserve water level. If the float is adjusted to a level that is too close to the height of the overflow pipe opening, any protrusion or splash of the water can cause the water level to fall and the tank to refill. Bend the float arm down, or turn the plastic screw over the mechanism to adjust the level of the lower float in the tank.