Parts of a toilet: a plumber’s glossary of every piece in the tank and bowl

By Ariel, last updated August 12, 2026.

Every homeowner learns the parts of a toilet the hard way, standing over an open tank at 11 p.m. trying to figure out why the thing will not stop running. This is the reference I wish people had before that moment. It names every piece in the tank and bowl, tells you what each one does, what it looks like, what fails first, and roughly what the replacement part costs at a hardware store. Bookmark it and come back to it whenever a toilet acts up.

TL;DR

A two-piece residential toilet has about a dozen parts that matter, split between the tank and the bowl. In the tank, the two you replace most are the flapper (the rubber seal that drops open when you flush) and the fill valve (the tower that refills the tank). A universal flapper like the Korky 2001 runs about $6 to $10, and a Fluidmaster 400A fill valve runs about $9 to $12. Those two parts fix the overwhelming majority of running-toilet and weak-refill complaints, and both are a 15-minute job with no tools beyond a sponge.

In the bowl, the parts almost never fail on their own. What fails is the wax ring underneath, the seal between the toilet and the floor drain. An Oatey wax ring costs about $5 to $10 and is the fix for water or smell at the base.

The single most common mistake is throwing money at the wrong part. People buy a whole new fill valve when only a 2-dollar seal failed, or a new toilet when a 6-dollar flapper would have done it. Learn the parts first, diagnose second, buy third. Prices here were observed at Home Depot, Lowe’s, and the Fluidmaster and Korky sites in August 2026.

What you actually need to know before diagnosing

A toilet is two water systems bolted together. The tank holds a measured charge of water and dumps it fast. The bowl uses that fast dump to create suction in a curved pipe and pull its contents into the drain. Nothing is pressurized inside the toilet itself. The only pressurized part is the supply line feeding the tank, and it is controlled by a shutoff valve on the wall.

Because there is no pressure inside the toilet, almost every failure is a seal that stopped sealing or a mechanism that stopped moving freely. Rubber hardens with age and chlorine exposure. Mineral scale builds up on moving surfaces. Plastic clips get brittle. That is the whole story of toilet repair, and it is why parts are cheap and jobs are short.

Two numbers govern how a modern toilet is built. Since 1994, federal law has capped residential toilets at 1.6 gallons per flush (GPF), and toilets that earn the EPA WaterSense label flush with 1.28 GPF or less, which is about 20 percent below the federal cap (EPA WaterSense). That lower water volume is why newer toilets rely on well-designed rim jets and a wide flush valve to move waste with less water. When a low-flow toilet flushes weakly, the cause is usually a partly clogged rim, not a design flaw.

One more thing before you open the tank. Turn off the shutoff valve on the wall, flush to empty the tank, and sponge out the last inch. You cannot see or feel most tank parts clearly with water in the way, and you will not diagnose anything staring at a full tank.

The parts of a toilet, grouped by system

I have grouped every part by the system it belongs to. For the major parts I list what it does, what it looks like, what fails first, and the current replacement cost.

Tank parts

Fill valve (also called the ballcock)

The fill valve is the vertical tower, usually on the left side of the tank, that refills the tank after each flush. Water comes up through it from the supply line, and it shuts off when the tank reaches its set level. Older toilets used a brass rod with a floating ball on the end, which is where the old name “ballcock” comes from. Modern fill valves use a plastic float cup that rides up and down the tower body.

What fails first is the internal seal and the diaphragm. When they wear, the valve either will not shut off fully (a toilet that runs or hisses forever) or will not open fully (a tank that fills slowly). A fill valve that whistles or screams is almost always the diaphragm.

The Fluidmaster 400A anti-siphon fill valve is the default replacement, around $9 to $12 at Home Depot, and it fits nearly every standard tank (Fluidmaster 400A at Home Depot, Fluidmaster). If you want a quieter refill, the Fluidmaster 400H PerforMAX runs about $14 to $16 (Home Depot), and the Korky 528 QuietFILL is about $8 to $10 (Korky). Full walk-through in our fill valve replacement guide.

Flapper and flush valve

These two work as a pair, so it helps to picture them together. The flush valve is the large opening at the bottom center of the tank, a plastic tube several inches across that leads down into the bowl. The flapper is the rubber flap that sits on top of that opening and seals it. When the flapper is down, water stays in the tank. When you flush, the flapper lifts and the tank empties through the flush valve.

The flapper is the single most-replaced part in any toilet. Rubber degrades, especially in tanks with in-tank cleaner tablets, and once it hardens or warps it stops sealing. A leaking flapper is the classic cause of a toilet that runs, refills on its own every few minutes (the “phantom flush”), or wastes hundreds of gallons a day silently.

A universal replacement like the Korky 2001 premium flapper costs about $6 to $10 (Korky, Home Depot 2001CM). Match the size to your flush valve opening: most older toilets use a 2 inch flapper, many newer high-efficiency toilets use a 3 inch. Our flapper replacement guide covers sizing.

Flush valve seat

The flush valve seat is the rim of the flush valve opening, the surface the flapper actually presses against. On many toilets it is molded into the flush valve as one piece. When mineral scale or a pitted surface develops on that rim, a brand-new flapper still will not seal, because the problem is the seat, not the flap. You can feel it: run a finger around the rim and it should be smooth. If it is rough or crusty, that is the leak.

The cheap fix is a seat repair kit (a stick-on ring the new flapper seals against) for about $5 to $8. The thorough fix is replacing the whole flush valve, which means pulling the tank off the bowl, so most people either use the repair kit or replace the toilet if it is old.

Overflow tube

The overflow tube is the open vertical pipe in the center of the tank, usually molded as part of the flush valve. Its job is safety: if the fill valve ever fails to shut off, water pours down the overflow tube into the bowl instead of onto your floor. The tank water level should sit about an inch below the top of this tube. If water is trickling into the tube constantly, your fill valve is set too high or is not shutting off.

The overflow tube almost never fails on its own. It matters mostly as a landmark for setting water level and diagnosing an overfilling tank.

Refill tube

The refill tube is the thin flexible tube, usually black or clear, that runs from the fill valve to the top of the overflow tube. It is easy to overlook, and it does something important: after a flush, it squirts a small stream of water down the overflow tube to refill the bowl to its proper standing level. The tank refills the tank; the refill tube refills the bowl.

If someone pushed this tube down inside the overflow tube (a common mistake), it can siphon tank water out continuously and cause phantom refills. It should clip to the rim of the overflow tube and point down into it, never below the waterline. This part rarely needs buying; it usually comes attached to a new fill valve.

Float

The float tells the fill valve when to stop. On modern valves it is a plastic cup that slides up and down the valve body. On older valves it is a ball on a metal arm. As the tank fills, the float rises, and at a set height it shuts the valve off. If your water level is wrong, you adjust the float, not the valve. On a cup-style Fluidmaster you pinch a clip and slide the cup; on a ball style you gently bend the arm. Full method in our float adjustment guide.

Floats fail by cracking and taking on water (a waterlogged ball sinks and the toilet overfills), or by binding on scale so they stop moving. A cup float that sticks half-open keeps the valve running.

Trip lever and handle

The trip lever is the handle on the outside of the tank and the arm that reaches inside. Press the handle, the arm lifts, the chain pulls the flapper open. The metal or plastic arm corrodes or cracks at the point where it threads into the handle, and the handle itself can strip. A universal replacement handle runs about $6 to $12. Note that the mounting nut inside the tank is reverse-threaded, so it loosens clockwise, which trips people up every time.

Lift chain

The small chain (or occasionally a plastic strap) connecting the trip lever to the flapper. Too much slack and the flapper will not lift enough for a full flush; too little slack and the flapper cannot seat fully, so the tank runs. The chain should have just a little slack when the flapper is closed. It is a common cause of both weak flushes and running toilets, and it costs nothing to adjust. Chains rust and break; a new one comes with any flapper.

Tank-to-bowl gasket

On a two-piece toilet, this is the large spongy rubber ring sealing the joint where the tank sits on the bowl. It sits around the flush valve outlet under the tank. When it hardens, you get a leak between the tank and bowl every time you flush, water running down the back of the bowl and pooling on the floor. A Korky 481BP tank-to-bowl gasket and hardware kit runs about $7 to $12 (Korky 481BP, Lowe’s). Replacing it means lifting the tank off, so most people do the tank bolts at the same time.

Tank bolts

Two (sometimes three) bolts running down through the bottom of the tank into the bowl, holding the tank on and compressing the gasket. Older sets are brass or plated steel with rubber washers. They corrode, and a corroded tank bolt is a slow leak or a bolt that snaps when you try to tighten it. Kits like the Korky 481BP above include fresh brass bolts and washers. Never overtighten these; porcelain cracks, and a cracked tank is a dead toilet.

Water supply line

The flexible hose running from the wall shutoff up to the bottom of the fill valve. Braided stainless steel lines are the standard now because the old rigid or vinyl lines fail. A braided line like a Fluidmaster toilet connector runs about $7 to $12 (Home Depot). The plastic coupling nuts crack over time; hand-tight plus a quarter turn is correct, and a wrench-cranked plastic nut is a future leak.

Shutoff valve (angle stop)

The valve on the wall or floor below the tank that cuts water to the toilet. Modern quarter-turn versions, like the BrassCraft G2 angle stop, turn 90 degrees to shut off cleanly and cost about $10 to $18 (BrassCraft at Home Depot, BrassCraft). Old multi-turn stops seize up and weep from the stem packing, and the classic homeowner discovery is that the shutoff will not shut off when you finally need it. If yours does not close fully, replace it before any tank work, and know where your home’s main shutoff is as a backup.

Bowl parts

The bowl is a single piece of glazed vitreous china with no moving parts. What look like separate components are shaped features of the casting. They rarely fail, but understanding them tells you why a toilet flushes well or poorly.

Rim and rim jets

The rim is the top edge you sit near, and it is hollow. Water from the tank enters the rim and pours out through a series of small holes on the underside called rim jets (or rim holes). These wash the bowl walls and start the swirl. Over years, mineral scale clogs these holes, especially in hard water, and a toilet that suddenly flushes weakly with water dribbling instead of rinsing the sides usually has clogged rim jets. You clear them with a piece of wire and a scale remover, not a new part.

Siphon jet

On many toilets there is a single larger jet at the front of the bowl bottom, aimed into the throat of the trapway. This siphon jet delivers a concentrated shot of water that helps trigger the siphon. Not every toilet has one (some use a wash-down design instead of a siphon-jet design), but on those that do, a clogged siphon jet means a lazy, incomplete flush.

Bowl sump

The sump is the low pool at the bottom of the bowl, the standing water you see. Its depth and surface area (the “water spot”) affect how clean the bowl stays and how well it handles waste before flushing. A larger water spot keeps the bowl cleaner but uses design tricks to stay within the 1.28 or 1.6 GPF limit.

Trapway

The trapway is the S-shaped or P-shaped channel inside the base of the toilet that carries waste from the sump up over a hump and down to the floor drain. That hump is what holds the standing water in the bowl and blocks sewer gas from coming up. The trapway is where clogs happen, because it is the narrowest point water and waste pass through. If a plunger will not clear it, a closet auger is the next step; see our unclogging guide.

You will see “fully glazed trapway” in toilet listings. It means the inside of the trapway is coated with the same slick glaze as the visible bowl. Bare casting inside the trapway is rougher and grabs waste, so a fully glazed trapway passes waste more smoothly and clogs less. It is a real advantage worth paying a little for on a new toilet, and it does not affect repair of an existing one.

Wax ring and closet flange

The closet flange is the metal or plastic ring fixed to the floor over the drain pipe, and it is what the toilet bolts to. The wax ring is the soft seal, shaped like a thick doughnut, that gets compressed between the bottom of the toilet and the flange when you set the toilet down. It seals the joint against both water and sewer gas.

Wax rings are the reason a toilet leaks or smells at the base. Wax dries out over decades, or the toilet rocks and breaks the seal. An Oatey Johni-Ring wax ring costs about $5 to $10 depending on whether you get the standard, the extra-thick, or the version with a plastic horn (Oatey 90230 at Home Depot, Oatey). Replacing it means pulling the toilet, which sounds worse than it is; our wax ring replacement guide walks it. If the toilet also rocks, fix that too, since a rocking toilet destroys a fresh wax ring; see how to fix a wobbly toilet.

Closet bolts

The two bolts that come up through the flange and pass through holes in the base of the toilet, holding it to the floor. They corrode and, like tank bolts, must not be overtightened, because that cracks the base. Fresh brass closet bolts come with most wax ring kits for a couple of dollars.

Seat and hinges

The seat and lid, mounted to the bowl with two hinge bolts through holes at the back of the rim. This is the one bowl part that is entirely replaceable and consumable. Hinges loosen, plastic yellows, and slow-close dampers wear out. Match the shape (round or elongated) to your bowl when replacing. We cover options in our best toilet seats roundup.

How a flush actually works, start to finish

Here is the whole cycle, tracing the water. Understanding it makes diagnosing almost any problem obvious.

1. You press the handle. The trip lever pivots and lifts the lift chain.
2. The chain pulls the flapper up off the flush valve seat. The flapper floats open on its own for a moment.
3. Tank water rushes down through the now-open flush valve into the bowl. A tank of water dumps in a few seconds, which is the entire point of having a tank.
4. That water enters the bowl through the rim jets and, on many toilets, a siphon jet. The rim jets rinse the walls; the siphon jet fires into the trapway throat.
5. The rush fills the trapway completely and pulls its contents over the hump. Once the trapway runs full, it siphons, and the siphon is what actually empties the bowl. That sucking finish at the end of a flush is the siphon breaking when air reaches it.
6. The tank empties, the flapper drops back onto the seat, and the flush valve is sealed again. Meanwhile the fill valve, which opened the instant the water level dropped, refills the tank. The refill tube sends a side stream down the overflow tube to restore the bowl’s standing water. As the tank fills, the float rises, and at the set level the fill valve shuts off. The toilet is ready again.

When any single step above is off, the symptom points straight at the part. A flapper that will not seat means step 6 never completes and the toilet runs. Clogged rim jets mean step 4 is weak and the flush is lazy. A float set too high means step 6 overfills and water trickles down the overflow tube.

Which part is causing your problem

Match your symptom to the likely part and the repair guide.

• Toilet runs constantly or hisses. Almost always the flapper not sealing (worn rubber or a bad flush valve seat), or a fill valve that will not shut off. Start with the flapper. See how to fix a running toilet.
• Phantom flush (tank refills by itself every few minutes with no one using it). A slow flapper leak letting tank water seep into the bowl, or a refill tube pushed down inside the overflow tube siphoning water out. Check both. Also running toilet.
• Weak or incomplete flush. Clogged rim jets or siphon jet (mineral scale), too little water in the tank (float set low), or too much slack in the lift chain so the flapper does not open fully. Clear the jets and check the chain first.
• Tank fills very slowly, or the valve whistles. A worn fill valve diaphragm or a partly closed shutoff. Replace the fill valve. See how to replace a toilet fill valve.
• Water or smell at the base of the toilet. The wax ring has failed, often because the toilet rocks. Replace the wax ring and stabilize the toilet. See how to replace a toilet wax ring and how to fix a wobbly toilet.
• Leak between the tank and bowl on a two-piece toilet. The tank-to-bowl gasket has hardened, or the tank bolts are loose or corroded. Replace the gasket and bolts as a set.
• Handle limp or the toilet will not flush at all. A broken trip lever arm or a disconnected lift chain. Reconnect the chain or replace the handle.

If you are planning a new toilet or a move rather than a repair, the measurement that governs everything is the rough-in; see our toilet rough-in guide.

Parts people replace unnecessarily

Diagnosing wrong costs money. These are the mistakes I see most.

Replacing the whole fill valve when only the seal failed. A fill valve that hisses or overfills often just needs its cap and seal cleaned or a $3 diaphragm seal, not a $12 new valve. Fluidmaster sells replacement seals for the 400 series. Pop the cap, rinse out the grit, and check before you swap the tower.

Buying a new flapper when the flush valve seat is the problem. If a fresh flapper still leaks, the seat is pitted or scaled, and the third and fourth flapper will leak too. Feel the rim. Use a seat repair ring, not another flapper.

Replacing a whole toilet for a running problem. A toilet that runs is a $6 flapper or a $10 fill valve, not a $300 replacement. Rebuild the tank first. The bowl almost never wears out; the tank guts do, and they are all cheap and universal.

Buying a matched brand-name repair kit when a universal part fits. You do not need the manufacturer’s proprietary flapper for most toilets. Universal Korky and Fluidmaster parts fit the vast majority of tanks for less. Match the flush valve diameter (2 inch versus 3 inch) and you are done.

Replacing the wax ring again and again without fixing the rock. If the toilet rocks, every new wax ring will fail. The wax is not the root cause; the loose toilet is. Shim and secure the toilet, then the wax ring lasts for decades.

FAQ

What are the two main systems in a toilet?

The tank and the bowl. The tank stores a measured amount of water and the mechanism to dump and refill it (fill valve, flush valve, flapper, float, handle). The bowl is a single glazed piece with no moving parts that uses the tank’s water dump to create a siphon in its curved trapway and pull waste to the drain. The two connect through the flush valve and, on a two-piece toilet, a tank-to-bowl gasket and bolts.

What is the difference between a fill valve and a flush valve?

They do opposite jobs. The fill valve brings water in and refills the tank after a flush, then shuts off when the tank is full. The flush valve lets water out, dumping the tank into the bowl when you flush. The flapper is the rubber seal on top of the flush valve. If your toilet runs, suspect the flapper or flush valve seal. If it fills slowly or will not shut off, suspect the fill valve.

What is a fully glazed trapway and does it matter?

The trapway is the internal S-shaped channel that carries waste out of the bowl. A fully glazed trapway has the same slick ceramic glaze on the inside as the visible bowl, so waste slides through instead of catching on rough bare casting. It genuinely helps a toilet resist clogs and is worth a small premium on a new toilet. On an existing toilet you cannot add it, so it only matters when buying.

Which toilet part fails most often?

The flapper. It is rubber, it sits in water constantly, and it degrades faster if you use in-tank cleaner tablets. A hardened or warped flapper stops sealing and causes running toilets and phantom flushes. It costs about $6 to $10 and takes 15 minutes to swap with no tools. The fill valve is a distant second.

How much does it cost to fix a running toilet in parts?

Almost always under $15. A universal flapper is about $6 to $10, and a fill valve is about $9 to $16 depending on model. Many running toilets are fixed by a free adjustment to the lift chain or float first. Buy the flapper only after you have ruled out a too-tight chain and a fill valve set too high. A whole tank rebuild kit, if you want to replace everything at once, is about $20 to $30.

Can I use a universal part or do I need the exact brand?

Universal parts from Fluidmaster and Korky fit the large majority of standard residential toilets, and they are usually cheaper than proprietary parts. The one thing you must match is the flush valve opening size for the flapper, either 2 inch (older and most common) or 3 inch (many newer high-efficiency toilets). Measure the opening or take a photo to the store. Pressure-assist toilets and some wall-hung and imported models use non-standard cartridges and do need specific parts.

Why does my toilet leak at the base?

The wax ring seal between the toilet and the floor drain has failed. Wax dries out over decades, or a toilet that rocks breaks the seal. Water appears around the base, sometimes only when you flush, and you may smell sewer gas. Replace the wax ring, and if the toilet rocks, shim and secure it first, because a rocking toilet will destroy a new wax ring quickly. An Oatey wax ring is about $5 to $10.

What is the overflow tube for?

It is a safety drain. The overflow tube is the open vertical pipe in the center of the tank. If the fill valve ever fails to shut off, water spills down the overflow tube into the bowl instead of overflowing onto your bathroom floor. It also receives the small refill stream that restores the bowl’s standing water after each flush. Your tank water level should sit about an inch below the top of the overflow tube.

Sources & references

• EPA WaterSense, residential toilets and the 1.28 GPF standard
• Fluidmaster installation help and fill valve support
• Korky toilet repair parts and flapper sizing
• Oatey flanges and wax rings
• BrassCraft water stops and supply lines

See also on My Best Toilet

• How to replace a toilet fill valve
• How to replace a toilet flapper
• How to fix a running toilet
• How to replace a toilet wax ring
• How to adjust a toilet float
• Toilet rough-in guide