Understanding the Parts of a Toilet


A flushing toilet is one of the simpler mechanical devices around your home, operating fairly flawlessly using a system that has no motors, requires no electricity (usually). It's a system that has been largely unchanged for centuries. Today's toilets may cosmetically look different from the first flushing toilet patented by Joseph Bramah of Yorkshire, England in 1778, but the operation is remarkably the same.

Yet despite its inherent simplicity, the actual operation of a flush toilet remains a mystery to many people, possibly because most of the magic occurs inside the porcelain tank, beneath a lid that rarely comes off.

Understanding the parts of your toilet and how they work can help you understand and address problems when they arise. With a bit of knowledge, you'll find that many problems can be solved rather easily without calling a plumber at all.

Touring Your Toilet

Begin simply by removing the lid of your toilet, setting it carefully aside, and closely examining the parts inside the tank. In the standard flush toilet—the type found in well over 95 percent of all homes—the parts will all be similar.

Handle and flush rod: The handle and flush rod are the parts that initiate the flush. As you study the handle, you'll see that it's attached to a horizontal rod that connects to a chain or wire. Toilet handles sometimes loosen, and the fix is usually simply to tighten the plastic or metal mounting nut located inside the tank. Be aware that this nut is threaded the opposite way from the way normal nuts are threaded. You tighten it on the handle tailpiece by turning the nut counterclockwise.

Lift chain (or lift wires): Extending out horizontally from the handle, a lift rod is connected to a chain that descends vertically to the bottom of the tank. This is the mechanism by which the flush valve at the bottom of the tank is opened to let the water flush down into the toilet bowl. A common problem with the lift chain is when it gets tangled or broken. When your toilet doesn't flush at all, or when it flushes incompletely, the problem is very often with a lift chain that is broken or needs adjusting

Flapper (or tank ball): The lift chain operates a rubber flapper that rests against the flush valve opening. (In older toilets, this may be a tank ball, instead.) You may not be able to clearly see the flapper with water in the tank, but its operation will become clear when you flush the toilet and watch the action. The flapper is operated when the toilet handle and lift chain lift it off the flush valve to allow the stored water in the tank to rush down into the bowl. Flappers eventually wear out or become misaligned, which can allow water to keep leaking down into the toilet bowl after the flush. A "running toilet" can often be traced to a faulty flapper.

Flush valve: This is the plastic or metal part sitting at the bottom of the tank, forming the opening through which water drops out of the tank and into the toilet bowl when a flush is initiated. The flush valve is usually connected to the vertical overflow tube as part of a one-piece construction. A large soft O-ring seal fits around the flush valve tailpiece below the tank, sealing and cushioning the joint between the tank and the bowl unit.

Overflow tube: Attached to the flush valve assembly, the overflow tube offers a safety measure to prevent water in the tank from overflowing should the water supply valve fail to shut off. Excess water will spill over the top of the overflow tube and down into the toilet bowl. A "running" toilet can be a sign that the water level in a toilet is too high.

Shutoff valve: Outside the toilet, on the water supply pipe that brings cold water to the toilet, there should be a fixture shutoff valve near the floor. Usually this is on the left side of the toilet, beneath the tank. This fixture shutoff valve allows you to shut off water to the toilet when you need to make repairs. Not all toilets have shutoff valves, but it is a good idea to install them. Over time, shutoff valves can fail, so replacing one is a fairly common DIY project.

Supply tube: Running from the shutoff valve to the water supply tailpiece on the bottom of the toilet tank is a vinyl, plastic, or steel mesh supply tube. These tubes are generally pretty trouble-free, but they can fail when they get old, or if the connections loosen.

Water supply valve (ballcock): Back inside the tank, the water supply valve, often known as the ballcock, is a vertical assembly, usually mounted on the left side of the tank. This is the focus of the toilet system, the part that opens the fresh water supply to refill the tank at the end of the flush cycle and closes again to shut off the water when it reaches the proper level in the tank. The supply valve is the place where many toilet problems originate, and replacing one when it fails is a very common project.

Float cup (or float ball): All supply valves have some kind of float device that serves to sense the water level in the tank and shut off the water supply valve when the proper level is reached. In older toilets, this may be a floating ball attached to a horizontal pivot arm running from the supply valve (see diagram above). In newer toilets, the float device is usually a float cup that is attached to the vertical shaft of the supply valve. Adjusting the float device is what allows you to adjust the water level in the tank.

Refill tube: Running from the water supply valve you will see a small flexible tube that clips to the top of the overflow tube in the center of the tank. This is the refill tube, and its purpose is to send a small trickle of water down into the toilet bowl during the refill cycle. This serves to replenish the standing water level in the bowl, which is essential for keeping the bowl trap sealed against sewer gases.

Toilet bowl: This, of course, is where the "action" occurs. But what most people don't see is that toilet bowl unit bolted to the floor has an internal curved trap structure that works just like a sink drain trap. The internal trap serves to hold standing water and prevent sewer gases from rising up into the home. The water you see in the bowl is actually the top mouth of the toilet's drain trap configuration. The trap is the place where that most common toilet problem of all occurs—drain clogs. If you tackle no other toilet repair, you almost certainly will deal with a clog at some point.

Wax seal (wax ring): Hidden from sight beneath the toilet, there is a soft wax ring that seals the connection between the bottom of the toilet (the horn) and the drain opening in the floor. This wax seal creates an airtight and water-tight seal between the toilet and sewer line. When it fails, you may notice water seeping out around the base of the toilet during a flush. Replacing a wax ring can be a somewhat messy job, but sooner or later, most toilets will need a new one.

How Your Toilet Flushes

If you watch inside the toilet tank with the lid removed during a flush cycle, you'll get a clear understanding of how the system works and where problems can occur.

  1. Pushing or pulling the handle lever operates a lift chain that lifts the flapper away from the flush valve opening. This starts the rush of water out of the tank down into the toilet bowl.
  2. The water in the bowl, along with its waste contents, is siphoned through the bowl's integrated trap and into the home's drain system.
  3. When the tank is empty, the flapper falls back into place in the flush valve opening.
  4. As the float cup or float ball drops in the tank, the water supply valve is opened, and freshwater begins to flow. Most of this water refills the tank, but a small amount is delivered back into the toilet bowl, through the refill tube and overflow tube.
  5. Once the float cup or float ball riding on the water level reaches the proper height in the tank, it shuts off the water supply valve. The toilet is now ready for the next flush.

You now have a clear understanding of your toilet's parts and their function. When problems occur, you'll likely know exactly where to look.