The model number is the fastest way to identify what parts your toilet actually needs. It’s how manufacturers separate one design from another, even when two toilets look almost identical from the outside. If you’re replacing a flapper, fill valve, trip lever, or flush valve, the model number helps you stay compatible and avoid wasting time on parts that don’t fit.
In this guide, you’ll learn where to find your toilet model number on most toilets, what to do if you can’t find it, and how to use that information to pick the right toilet replacement parts. You’ll also get a quick breakdown of common toilet part names so you can confidently identify what you’re looking at inside the tank.
Quick Answer: Where Is the Toilet Model Number?
Most toilet model numbers are stamped or printed inside the tank, on the back wall near the water line, under the tank lid, or on the back of the bowl near the tank connection.
If the marking is faded, use a flashlight and check for porcelain stamps or ink markings.
Why the Model Number of Your Toilet is Important
Accurate Repairs and Replacements: Toilet parts are not always interchangeable, and the model number ensures you get parts that match your exact toilet instead of guessing.
Model Variations Over Time: Even within the same toilet line, manufacturers make internal changes over the years that can affect which parts fit correctly.
Faster Troubleshooting and Ordering: A model number removes guesswork when speaking with a plumber or parts specialist, speeding up identification and helping pick correct parts.
Warranty and Support: If your toilet is under warranty, the model number is required for claims, replacements, and manufacturer support.
Maintenance Accuracy: Some models have specific maintenance or compatibility requirements.
Simple Steps to Find the Model Number
Start Inside the Toilet Tank: Carefully remove the tank lid and look along the back wall, side walls, near the water line, or around the flush valve area. The number may be stamped into the porcelain or printed in ink. If it’s difficult to read, use a flashlight and wipe away any mineral buildup with a damp rag.
Check the Toilet Bowl: If you don’t find the model number inside the tank, check the bowl. Some manufacturers place identifying information under the rim or on the back of the bowl near the tank connection (more common on older toilets and certain one-piece models).
Look Under the Tank Lid: Flip the tank lid over and check the underside. In some cases, you’ll find a marking that helps identify the toilet. It’s not always the full model number, but it can still be useful when you’re narrowing down replacement parts.
Manufacturer's Website: If you can't find the model number on the toilet, check the manufacturer's website. They often have resources to help you identify your model based on the toilet's design and features.
Still Can’t Find It? Take a few clear photos of the inside of the tank, especially around the fill valve and flush valve areas. Our customer support team can help confirm the toilet model and point you toward compatible replacement parts without the guesswork.
Quick Guide to Toilet Parts
Most people don’t just need a model number. They also need to identify what part is failing. Here are the most common toilet part names you’ll run into:
Fill Valve: Refills the tank after each flush. If your toilet is running, hissing, filling slowly, or filling inconsistently, the fill valve is often the culprit.
Flapper (or Seal): Seals the flush valve opening. When it gets warped, slimy, stiff, or cracked, the tank can leak water into the bowl and run randomly. Flappers are “universal” in a lot of cases, but size and style still matter.
Flush Valve: The assembly that releases water from the tank into the bowl during a flush. The size is commonly 2” or 3”, and that sizing impacts which flappers and kits will work.
Trip Lever (Handle): Connects to the chain or mechanism that lifts the flapper or activates the flush system. Handle mounting position matters more than people expect, especially with side-mount, angled, or oddball placements.
Tank-to-Bowl Gasket and Bolts (Two-Piece Toilets): If you have a two-piece toilet and you notice moisture at the seam between tank and bowl, the gasket and bolts deserve a close look. Old bolts corrode, gaskets compress, and leaks can start slowly.
Supply Line: Feeds water from the shutoff valve to the toilet. If you’re replacing the fill valve, replacing the supply line at the same time is a smart best practice because it’s cheap insurance against leaks.
If you’re already in the tank for one repair, take a quick look at the other wear parts too. On older toilets, replacing a couple items together often means fewer leaks, fewer phantom runs, and a more reliable flush.
Universal Toilet Replacement Parts
“Universal” toilet parts aren’t magic parts that fit every toilet ever made. In the plumbing world, universal usually means it fits the most common gravity-flush toilets that use standard 2” or 3” flush valve openings.
You can avoid almost every wrong-part scenario with one quick check: simply lift the flapper and measure the diameter of the flush valve opening straight across inside edge to inside edge with a tape measure or ruler. Once you know the size, choosing replacement parts becomes much easier.
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Flappers
A worn flapper is one of the most common causes of a running toilet. If the rubber is stiff, warped, or no longer sealing consistently, replacing it is usually a quick fix.
For standard 2” gravity-flush toilets, the Fluidmaster PerforMAX Adjustable Toilet Flapper and Lavelle Vinyl Flapper are both dependable replacements that fit many common toilet models.
For toilets with a larger 3” flush valve opening, the Korky Universal Toilet Flapper is widely used because it adjusts easily and works across many newer toilet designs.
Fill Valves
The fill valve controls how the tank refills after each flush. If the toilet runs intermittently, fills slowly, or makes hissing noises long after flushing, the fill valve is often the problem.
The Fluidmaster PRO45 Fill Valve is a reliable replacement for many standard toilets because it adjusts easily, installs cleanly, and holds up well over time. The Korky PRO GRADE 528PRO Fill Valve works especially well in tighter toilet tanks where space around the trip lever can become an issue. Its compact design makes installation easier in slimmer tank layouts.
If several toilets in the home are around the same age, the Fluidmaster 400A Contractor 3-Pack can be a practical option to keep extra fill valves ready for future repairs.
Flush Valves
If the flush valve is cracked, scaled, or no longer sealing properly, replacing the full assembly can solve recurring leak and flushing issues more reliably than replacing the flapper alone.
The 2” Fluidmaster PRO57K Complete Flush Valve Kit is a popular choice for many older flapper-style toilets because it includes the flush valve, flapper, gasket, and tank-to-bowl hardware in one package. The 2” Korky Adjustable Flush Valve & Gasket Kit is another solid option, especially for toilets that benefit from adjustable overflow height and additional tank bolt support.
For many newer toilets that use larger flush openings, the Korky 3” Adjustable Flush Valve & Tank-to-Bowl Gasket Kit is commonly used across a wide range of flapper-style models manufactured since the early 2000s.
Trip Levers
Trip levers seem simple, but mounting angle and tank layout matter more than most people expect.
The Korky StrongARM Trip Lever is popular because it adjusts to fit front-mount, side-mount, angled, and right-hand tank configurations without much trial and error. It’s also available in Chrome, Brushed Nickel, and Matte Black for matching bathroom hardware.
When to Call in an Expert
If you’re dealing with a leak at the tank-to-bowl seam, a toilet that’s cracked, or a setup where parts don’t match what you expected, don’t keep forcing it. Porcelain doesn’t forgive much. Over-tightened bolts can crack a tank, mismatched gaskets can cause slow leaks that rot subfloors, and the wrong flush valve setup can turn into repeat repairs.
If you can’t find the model number and you’re not confident about sizing, it’s smart to get a second set of eyes on it. Sometimes that means calling a plumber. Sometimes it just means sending photos to a parts expert so you don’t buy the wrong thing.
FAQ
Where to find toilet model number?
Most toilets have the model number stamped or printed inside the tank, usually on the back wall or side wall. If you don’t see it there, check the bowl and the underside of the tank lid.
Is a toilet serial number the same as the model number?
No. A toilet serial number usually tracks manufacturing. The model number identifies the toilet design and helps match compatible parts.
Where to find Kohler toilet model number?
The Kohler toilet model number location is most often inside the tank. If it’s not there, check the underside of the tank lid and the back of the bowl near the tank connection.
What about TOTO toilet model number location?
For most TOTO toilets, start inside the tank first. If markings are faint or missing, checking the bowl and sending photos is often the quickest path.
Do universal toilet parts fit every toilet?
Not every toilet. Universal parts cover most standard tank designs, but proprietary canister systems and uncommon setups can require model-specific parts.
What if I’ve got an older toilet like Mansfield toilets?
Older toilets can have faint stamps or discontinued models. Photos of the inside of the tank and the flush valve size usually help narrow down compatible options.
Find The Model Number On Your Toilet Today!
Finding your toilet model number is the quickest way to take control of a repair. Once you have it, you can match the right parts, avoid wrong-size surprises, and choose replacement parts that are built to last.
If the stamp is missing or the tank is confusing, you’re not stuck. A couple photos and a quick message to Plumbing Deals support can save you from buying parts twice. To speak with one of our plumbing specialists and get guidance before you place your order, call our toll-free line at 1-888-682-5956.
When you’re ready to fix it or upgrade your setup, we’ll help you get the right parts and products to keep everything straightforward!
