How a Toilet Works, Plumbing Diagrams & Repair Tips
It’s easy to take a toilet for granted–at least until something goes wrong with it. But when a toilet threatens to overflow, runs incessantly, or leaks onto the floor, we gain a full appreciation of what it means to have it working properly.
This site, Toilet-Repairs.com, is a one-stop resource for free, expert advice about toilet repair and care. We’ll help you handle your own repairs or point you to qualified local pros when the job is beyond your reach.
Many toilet repairs can be surprisingly quick and easy for do-it-yourselfers–and doing your own repairs often makes sense, for a couple of reasons: 1) You can save the $80 or more per hour that a plumber would cost, and 2) you can take care of the problem immediately, without waiting for a plumber to arrive. To handle many basic toilet repairs, you just need a few tools, such as a toilet plunger, pliers, screwdriver, and wrench.
Before you begin, it’s important to become familiar with the basic workings of a toilet.
How a Toilet Works & Toilet Plumbing Diagrams
The simple but ingenious mechanics of the toilet have changed very little since the earliest “water closet” was invented in the 19th century.
The toilet, though not one of the more glamorous of home fixtures, is designed to do a very specific job–to carry away waste and prevent sewer gases from entering the house. And unless something goes wrong with a toilet, it handles its job adroitly.
As shown in the illustrations at right and below, a toilet has two main parts, both made from vitreous china: a tank and a bowl. Some toilets are cast as a single piece while others are made in two separate parts that are joined together.
The tank, which houses all of the working parts, is where various types of toilets differ the most. Several different kinds of mechanisms may be used to accomplish a toilet’s basic operation. Following is a description of how the most common mechanism works:
When a toilet is ready for use, both tank and bowl are partly filled with water. Passages between the bowl and the closet bend form a trap that remains filled with water at all times, blocking the rise of sewer gases.
When you flush the trip lever, it lifts a rubber stopper–called a tank ball, flush valve seat ball, or the newer, more effective, flapper or flapper ball–from the flush valve, letting the water in the tank flow into the bowl.
The pressure of the cascading water forces the bowl’s water and waste down the waste pipe. The water flowing into the bowl also cleans the bowl. The bowl’s water is replenished by water entering from the tank through a supply tube that connects to the home’s cold water supply piping.
The flush valve and the flapper together are called–not surprisingly–the flapper valve. A flush valve is 2 1/2 inches in diameter, as is the ball-shaped part of the flapper. The flapper hinges onto the vertical overflow pipe that’s next to the valve, and a small chain connects the flapper to the trip lever.
The advantage of a flapper over the earlier stoppers is that it doesn’t have as many parts to foul or get hung up, so it’s less likely to let the tank “run” or leak into the bowl.
As the tank of a conventional toilet empties, a float ball drops, activating the ball cock (simply a water valve), which releases water into the tank. Some new ball cocks operate on water pressure–they don’t have a float ball.
The water is delivered to the ball cock through the previously mentioned supply tube, which is connected to a valve at the wall or floor. This valve goes by various names, including stop valve, supply valve, and shutoff valve. When turned clockwise, this valve shuts off the flow of water to the tank. To prevent overflow and flooding, the top of the overflow tube is open and acts as a drain if the tank’s water level rises too high.
In today’s water-conserving toilets, a minimum-flush mechanism seals the flush valve seat when the tank is still partially full, keeping full pressure on the flush but using less water. A pressurized cylinder inside the toilet tank cuts water usage by putting a small amount of flush water under pressure–either from compressed air orfrom the house supply line’s water pressure. A pressure-activated ball cock is activated by a drop in the tank’s water pressure. This type, easily adjusted to deliver various amounts of water to the tank, eliminates the need for a float.
The conventional float-ball, lift-wire, and tank-ball mechanism has been the standard flushing device for many years. The cut-away view above shows the relationship of the tank to the bowl and how the toilet’s base forms a trap to block sewer gases. The flush handle raises the trip lever, raising the flush valve or seat ball from the flush valve seat, letting water rush in to the bowl.
The illustration at left shows a typical flapper combined with a pressure-activated ball-cock valve. The illustration at right
shows the older style of float ball with a standard ball cock. When the float ball drops, the ball cock opens, filling the tank until the ball floats back into its upper position. The overflow tube sends excess tank water to the bowl. The refill tube replenishes water in the tank through the overflow tube.