A toilet consists of a tank, a bowl (with some models these are one piece) and ball-cock and flush-valve assemblies which are, respectively, the fill and flush devices inside the tank.

Most people believe that a gravity-flush toilet works on water pressure. Not so. In fact, there is no single factor that makes for a full flush, but rather many components working in harmony. Often, when only one of these components fails to do its job, the whole operation falls apart.

The flush-related component that most of us are familiar with is the handle that triggers the flushing action. What happens beyond that is, for most, a mystery.

The handle is connected to a trip lever. When pressed, the handle raises it which, in turn, raises a chain or vertical rod that is attached to a stopper located at the bottom of the tank.
When the stopper is raised, water in the tank rushes through the large hole (the flush valve) at the bottom of the tank. It then travels into the bowl via the small flush ports at the underside of the rim of the bowl.

Then physics takes over. Gravity pulls (or siphons) the water in the bowl out through the trap and into the drainpipe. Once the tank has emptied, the stopper drops back into the flush-valve seat and the float ball (now down) triggers the ball-cock assembly to refill the tank with new water.

Water enters the toilet through the supply line located below and to one side of the tank and then through the tank-fill tube. As the water level rises, so too does the float ball. When the ball reaches a certain height, it shuts off the flow of water. If the water fails to stop running, the tank will not overflow because water will go into the overflow tube and then into the toilet bowl. This results in the irritating "running toilet."

This condition can be the result of several things. One of the most common is a float arm that is not rising to the proper height. The simplest method to correct this is to slightly bend the float arm downward.

Another common cause is a stopper that is not seating properly against the flush valve seat. Generally, this is due to deterioration of the stopper, or a flush-valve seat that is damaged or covered with scale. Stopper replacement or cleaning and repair of the flush-valve seat will usually solve the problem.

A cracked overflow tube and defective ball-cock valves also often are the culprits. While both of these can be repaired, often your best bet is to replace them. Some of the older ball-cock devices do not contain an anti-siphon valve that prevents water in the tank from being siphoned back into the freshwater system. All new fill valves contain the anti-siphon feature. In addition, the search for and replacement of parts can cost more and take significantly longer to replace than to replace the entire assembly.

If you suspect that your toilet is leaking, you can find out by using the food-coloring test. Place a few drops of coloring into the tank and allow the toilet to go unused for one half-hour. If, upon your return, coloring has shown up in the bowl, you have a leak. One of the aforementioned remedies should solve the problem.

An insufficient flush is the result of several things: Faulty linkage between the flush handle and the trip lever; the tank stopper closes before the tank is emptied; the flush passages or "siphon jets" are clogged with mineral buildup or a leak exists between the bowl and the tank.

The repairs are not as difficult as one might think. Replacing one or both of these components can repair the faulty linkage between the flush handle and the trip lever. A tank stopper that closes prematurely generally can be corrected by changing the length of the chain or adjusting the rod between the trip lever and the stopper. Occasionally, a defective stopper is the cause.

Mineral-clogged flush passages can be opened by using a bent coat hanger. Insert the end into each of the passages to dislodge the material. Another means of dispensing of scale involves a quart of vinegar and some duct tape.

Turn off the water to the toilet and empty the tank. Next, use the duct tape to seal the flush passages under the rim of the toilet. Pour the vinegar into the flush valve and allow it to remain overnight. Remove the tape and use a stiff nylon brush to remove the residue that remains. Turn on the water and refill the tank.

A leaking tank is a sign of loose fittings or worn washers. A new washer or a modest turn of the wrist is all that is required.

A sweating toilet is not an indication that it has been working too hard, but, rather, is a sure sign of condensation. This condition can be corrected by installing a tank liner. The liner will act as an insulation barrier between the water in the tank and the temperature in the home.

For extremely cold climates, there are hot-water mixing valves that introduce a small amount of hot water into the tank. Also, there are toilets with trap heaters to prevent water in the trap from freezing.