Toilet Parts Diagram: Every Component Labeled and Explained

Before diving into individual components, it helps to understand that a toilet's parts belong to one of two zones: the tank (the rectangular box at the back) and the bowl (the basin you sit on). Each zone has its own subsystems, its own set of common failure modes, and its own replacement parts.

The tank stores a precisely measured volume of water, typically 1.28 gallons on a modern EPA WaterSense-certified toilet or 1.6 gallons on older models. When you press the handle or button, that water releases rapidly into the bowl, creating the pressure needed to push waste through the trapway and into the drain. The bowl then refills from a separate stream routed through the fill valve. If any link in that chain breaks down, you get incomplete flushes, ghost flushing, running water, or outright clogs.

For a deeper look at how these systems work together, see our guide on how toilets work and our overview of flush type differences.

1. Fill Valve (Ballcock)

The fill valve is the vertical assembly on the left side of the tank that refills the tank with fresh water after every flush. Older toilets use a float-ball ballcock design: a large rubber ball sits on an arm, and as the water rises the ball lifts until it shuts the valve. Modern toilets use a float-cup fill valve, where a cylindrical float slides up a vertical shaft. Float-cup valves are quieter, more precise, and easier to adjust.

Brands like TOTO, Kohler, and American Standard all ship their own OEM fill valves, but universal replacements from Fluidmaster (the 400A and 400AH models) are compatible with virtually every toilet on the market. A hissing sound after the flush cycle ends, slow tank refilling, or water rising above the overflow tube all point to a failing fill valve.

2. Flapper

The flapper is a rubber seal seated at the bottom of the tank over the flush valve opening. When you flush, the trip lever lifts the flapper via a chain, allowing water to drop into the bowl. Once the tank empties, the flapper drops back down and seals the opening so the tank can refill. Flappers are made from rubber or silicone, and they degrade over time from chloramines in municipal water, hard water mineral deposits, and cleaning tablet chemicals.

A flapper that no longer seals correctly causes "ghost flushing" or a toilet that runs constantly. The fix is almost always a $5 to $8 flapper replacement. The critical spec to check is the flapper seat diameter: most toilets use a standard 2-inch flapper, but high-flush models like the American Standard Champion 4 use a 3-inch flapper for a faster, more powerful release. Matching the correct size is essential; a 2-inch flapper on a 3-inch seat will never seal properly.

See our dedicated toilet flapper guide for sizing charts and brand-specific compatibility.

3. Flush Valve

The flush valve is the tube and seat assembly at the center-bottom of the tank. It includes the valve seat (the ring the flapper seals against), the overflow tube, and sometimes a tower-style tower assembly in tower-flush designs. The flush valve determines how quickly water exits the tank and how much pressure reaches the bowl. A wider flush valve opening allows more water to flow in less time, which is why toilets with 3-inch flush valves typically score higher on MaP flush testing than comparable 2-inch models.

TOTO's flush valve design in the Drake series routes water through a siphon-jet system that concentrates flow at the siphon jet hole at the base of the bowl, helping the toilet achieve MaP scores of 1,000 grams (maximum rating) on models like the Drake II (CST454CEFG). Kohler's Class Five flush valve in the Cimarron takes a similar approach, pushing water through a wider tower to maximize velocity.

4. Overflow Tube

The overflow tube is the tall, open-topped standpipe attached to or adjacent to the flush valve. Its job is to act as a safety drain: if the fill valve malfunctions and water keeps rising, the overflow tube channels the excess water down into the bowl rather than letting it spill over the tank rim and flood the floor. The water level inside the tank should sit approximately 1 inch below the top of the overflow tube. If water is trickling into the overflow tube constantly, the fill valve float is set too high or the valve is failing.

5. Trip Lever and Handle

The trip lever is the arm that connects the external handle (or button) to the flapper chain. Pressing the handle rotates the trip lever arm, which lifts the chain and flapper. Trip levers are made from plastic or metal, and plastic versions crack over time especially in hard-water regions. A loose or broken handle is one of the simplest toilet repairs: most universal trip levers (sold as a lever-and-nut assembly) install in under five minutes by unthreading the mounting nut inside the tank. Note that the nut is reverse-threaded on most toilets and tightens counter-clockwise.

6. Tank-to-Bowl Bolts and Gasket

Two (sometimes three) bolts with rubber washers pass through the bottom of the tank and thread into the toilet bowl below, with a large sponge rubber donut gasket creating a watertight seal between the tank and bowl. When these bolts corrode or the gasket hardens and shrinks, water seeps from the joint between tank and bowl. A complete tank bolt kit (bolts, washers, nuts, gaskets) typically costs under $15 and takes about 20 minutes to replace.

7. Toilet Handle (Trip Lever External)

The external handle or push button triggers the flush. Two-piece toilets like the TOTO Drake and Kohler Highline typically use a side-mounted lever handle. One-piece toilets like the Woodbridge T-0001 or Swiss Madison St. Tropez more commonly use a top-mounted chrome button or dual-flush push button. The button connects to the trip lever or dual-flush tower mechanism inside.

8. Toilet Bowl

The porcelain bowl is the main basin that holds water between flushes and channels waste into the trapway during a flush. Bowl shape affects both comfort and flushing efficiency. Elongated bowls (measuring about 18.5 inches front to back) provide more seating area and typically accommodate a better siphon jet position. Round bowls (about 16.5 inches front to back) save 2 inches of floor space, which matters in smaller bathrooms.

Bowl surface quality significantly affects long-term performance. TOTO coats its bowls with CeFiONtect glaze, an ionized surface treatment that reduces particle adhesion so waste slides cleanly. Kohler's CleanCoat and American Standard's EverClean surface serve the same purpose. An uncoated bowl accumulates mineral deposits and staining faster and requires more aggressive cleaning chemicals.

9. Trapway

The trapway is the S-shaped or P-shaped internal channel molded into the back of the bowl that creates the water seal and directs waste to the floor drain. It is the single most important factor in clog resistance. A larger trapway passage allows larger solids to pass without obstruction. The American Standard Champion 4 uses a 2.375-inch fully glazed trapway, one of the largest in the residential market. The TOTO Drake II uses a 2.125-inch fully glazed trapway. The Kohler Highline Arc uses a 2.125-inch trapway as well.

The term "fully glazed" means the glaze coating extends through the entire interior of the trapway, not just the bowl. Fully glazed trapways resist waste adhesion and maintain consistent flow resistance over years of use. Partial glazing or unglazed trapways develop rough surfaces that catch debris and contribute to chronic clogging.

Our guide on trapway size covers measurement, comparison by model, and what to look for if you deal with frequent clogs.

10. Siphon Jet

The siphon jet is a precisely angled hole at the base of the bowl, positioned directly below the trapway entrance. It directs a concentrated stream of water toward the trapway opening during a flush, which is what initiates the siphon action that pulls waste and water through the trap. The size, angle, and surface finish of the siphon jet are engineered by each manufacturer and are one of the key variables that distinguish a 500-gram MaP score from a 1,000-gram MaP score.

A blocked siphon jet is a common cause of weak flushing. Mineral deposits, particularly calcium carbonate in hard-water areas, can partially or fully block the jet opening over time. Cleaning with a toilet bowl cleaner containing hydrochloric acid or diluted muriatic acid typically dissolves these deposits. See our resource on clearing blocked jet holes for step-by-step instructions.

11. Rim Holes (Rim Jets)

Rim holes are small openings around the underside of the toilet bowl rim that release water during a flush to rinse the interior bowl surface. A standard two-piece toilet has between 12 and 20 rim holes depending on bowl size. The angle and direction of each hole is engineered to create a swirling or directional rinse pattern. TOTO's Tornado Flush design replaces traditional rim holes with two angled nozzles that create a powerful cyclone of water around the bowl, which eliminates the hard-to-clean rim area entirely and is one reason TOTO consistently scores near 1,000 grams on MaP testing.

Like the siphon jet, rim holes can clog with mineral deposits. If water dribbles from the rim rather than jetting, the rim holes may be partially obstructed.

12. Bowl Water Level

The standing water level inside the bowl (between flushes) is determined by the height of the trapway's highest internal point, which is called the weir. The bowl water level typically sits between 2 and 4 inches above the floor of the bowl. A bowl with a larger water surface area is often considered more hygienic because waste is more likely to land in water rather than on dry porcelain. The fill valve controls tank refill, but the bowl refill tube (a small auxiliary tube that runs from the fill valve body to the overflow tube) is what replenishes the bowl water level after each flush.

13. Wax Ring

The wax ring is a molded ring of plumber's wax that creates a watertight and gas-tight seal between the bottom of the toilet bowl outlet and the top of the floor flange. It compresses under the weight of the toilet when the toilet is set in place. Wax rings are a single-use component: once compressed, they cannot reseal if the toilet is removed. Any time a toilet is pulled up (for floor replacement, flange repair, or repositioning), the wax ring must be replaced with a new one.

Standard wax rings are approximately 3 inches tall when uncompressed. When the floor flange sits below the finished floor level (a common issue after tile installation), an extended wax ring or a wax ring with a plastic extension horn bridges the gap. Gerber, TOTO, Kohler, and American Standard all recommend their respective OEM wax rings, but generic plumber's wax rings from any hardware supply chain perform identically.

14. Floor Flange (Closet Flange)

The floor flange is the circular fitting secured to the subfloor that connects the toilet drain to the household drain-waste-vent system. It is typically made from PVC (in modern installations), cast iron (in older homes), or ABS plastic. The flange provides the anchor points for the two closet bolts (also called T-bolts or johnny bolts) that hold the toilet base down. A cracked or corroded flange allows the toilet to rock, which in turn damages the wax ring seal and leads to floor-level leaks and sewer gas infiltration.

Closet bolts sit in slots on the flange and can be repositioned before setting the toilet. After the toilet is set and leveled, the protruding bolt ends are cut to length and capped with decorative plastic covers. Our toilet flange repair guide covers both PVC and cast-iron flange scenarios.

15. Supply Line

The supply line is the flexible hose that connects the shut-off valve (angle stop valve) on the wall or floor to the fill valve inlet at the bottom of the tank. Most modern supply lines are 12 or 16 inches long, braided stainless steel over a rubber core, and terminate in 3/8-inch compression fittings. Older homes may have rigid chrome or copper supply tubes that are less flexible and more prone to cracking at connection points.

A supply line that drips at either connection point is typically resolved by hand-tightening the fitting, then a quarter-turn with pliers. Over-tightening plastic fill valve nuts cracks them. Braided stainless lines should be replaced every seven to ten years or any time the rubber core shows external cracking or swelling.

16. Shut-Off Valve (Angle Stop Valve)

The shut-off valve (formally called an angle stop or straight stop depending on pipe orientation) is mounted to the wall or floor directly behind or beside the toilet and allows you to stop water flow to the toilet without shutting off the whole house water supply. It connects to the home's copper or CPVC supply piping on one side and the toilet supply line on the other. Most angle stops use a quarter-turn ball valve or a multi-turn compression valve.

A shut-off valve that fails to fully close (a common problem in homes over 20 years old) makes any toilet repair much harder because you must shut off water at the main. Replacing an aging shut-off valve is a low-cost preemptive repair that costs under $20 in parts. Our shut-off valve guide covers installation and recommended brands.

17. Toilet Seat

The toilet seat contacts the user and provides comfort and hygiene. Seat materials include polypropylene plastic (most common), wood composite (warmer to the touch), and thermoset (a dense plastic that resists scratching). Elongated seats measure approximately 18.5 inches from hinge to front tip; round seats measure about 16.5 inches. Mismatching a round seat on an elongated bowl or vice versa leaves gaps that create comfort and hygiene problems.

Soft-close seats use a damped hinge mechanism that prevents the seat from slamming shut. This is now a standard feature on most seats in the $30-and-above category. TOTO's SoftClose seats and Kohler's Grip-Tight bumpers represent two different engineering approaches to the same goal.

18. Seat Hinges and Mounting Hardware

Standard seat hinges bolt to the toilet bowl through two holes located at the back of the bowl rim, typically 5.5 inches apart (center-to-center). Some European-style toilets use a different hole spacing, so confirm your bolt hole spread before ordering a replacement seat. Hinge bolts are typically plastic or stainless steel, with plastic wing nuts that tighten by hand. Corrosion of metal hardware in humid bathrooms is one of the most common reasons a toilet seat loosens over time.

19. Toilet Lid

The lid covers the toilet tank (not to be confused with the seat lid that covers the bowl). The tank lid is a solid piece of porcelain that rests on the tank rim without being fastened. It can be lifted to access internal components for inspection or adjustment. Keep in mind that toilet lids are brand-, line-, and model-specific: a Kohler Highline Arc lid is not interchangeable with a Kohler Cimarron lid even though they are from the same manufacturer. OEM replacement lids are available directly from manufacturers or plumbing supply houses.

Two-piece toilets like the TOTO Drake (CST776CEFG), Kohler Highline (K-3978), American Standard Cadet 3, and Gerber Viper ship the tank and bowl as separate components that bolt together during installation. This design makes shipping, installation, and individual-component replacement easier. If the tank cracks on a two-piece toilet, you can replace just the tank. On a one-piece toilet like the TOTO UltraMax II (MS604114CEFG), a cracked tank means replacing the entire toilet.

One-piece toilets like the Woodbridge T-0001 and Swiss Madison St. Tropez (SM-1T803) tend to use proprietary flush valves and fill valves, which can make parts sourcing more difficult after the product line is discontinued. When purchasing a one-piece toilet, confirm that the manufacturer sells replacement internal components as a parts kit rather than requiring full-unit replacement.

Wall-hung toilets present a third configuration: the bowl is wall-mounted and the tank (called a carrier frame or in-wall tank) is hidden inside the wall cavity. Parts access requires opening the in-wall access panel. The Geberit in-wall tank system is the most widely installed in North America and has good parts availability, but general-contractor-level plumbing knowledge is typically needed for tank-internal repairs.

Since 2006, EPA WaterSense certification has required toilets to use no more than 1.28 gallons per flush (GPF) while maintaining a minimum MaP flush performance score of 350 grams. This standard forced manufacturers to redesign every component in the flush pathway to deliver adequate clearing power with one-quarter less water than the legacy 1.6 GPF standard. The result is a generation of internal components engineered to precise tolerances that older universal replacement parts may not match.

Specifically, the flush valve seat diameter, flapper geometry, and overflow tube height are interdependent on WaterSense-certified toilets. Installing a generic 2-inch flapper on a toilet engineered for a specific tower-flush valve can cause chronic incomplete flushes. On premium models like the TOTO Drake II and Kohler Cimarron, TOTO and Kohler publish OEM part numbers for every tank internal component, and many plumbing supply houses stock them alongside universal aftermarket options.

For the highest-performing WaterSense models by MaP score, see our complete list of the best flushing toilets with MaP data by model.

Dual-flush toilets add a layer of complexity to the standard tank assembly. Instead of a single flapper and handle, they use one of two mechanisms: a tower-flush (or canister-flush) system controlled by a dual push button on the tank lid, or a dual-flush trip lever that controls a modified flapper with two-position lift. The TOTO Aquia IV and Woodbridge T-0001 use tower-flush designs. The American Standard H2Option uses a dual-flush trip lever.

Dual-Flush Tower Valve

A tower valve (also called a canister valve) replaces the flapper with a cylindrical tower that lifts straight up when the flush button is pressed. The height it lifts determines whether it is a partial flush (0.8 GPF) or a full flush (1.28 GPF). Two separate push buttons on the tank lid connect via cables to a mechanism inside the tower. Tower valves have more moving parts than flappers and generally a higher replacement cost (typically $20 to $50 for an OEM tower assembly) but they seal more reliably than traditional flappers because the seal is a gasket on the base of the tower rather than a flexible rubber flapper.

Dual-Flush Fill Valve

The fill valve on dual-flush toilets is functionally identical to single-flush models but may be set to a lower float position (since the full-flush volume is 1.28 GPF rather than 1.6 GPF). Misadjusting the float height on a dual-flush toilet is one of the most common causes of incomplete liquid-waste flushes: if the tank is not filling to the correct level before the partial flush, there is insufficient water volume to clear the bowl. The correct water level is marked on the inside of the tank wall on most models.

Professional plumbers consistently recommend keeping three toilet parts on hand as low-cost insurance against late-night emergencies: a replacement flapper matched to your toilet model, a universal fill valve (Fluidmaster 400AH or equivalent), and an extra supply line. These three items cost under $40 combined and cover the vast majority of non-structural toilet failures. If your household has a toilet over 10 years old, adding a wax ring and a set of tank bolts to that supply list covers the most common floor-seal failures as well.

Model-specific parts (flush tower valves, OEM fill valves for TOTO or American Standard, specific flapper sizes) are worth sourcing before you need them if your toilet is outside standard configurations. TOTO's part finder tool at TOTO USA's website cross-references model numbers to part numbers. Kohler offers the same through their parts catalog. American Standard cross-references parts at as.com.