How to Find Your Toilet Model Number [2026]

Pop the tank lid to fix a running toilet or order a new flapper, and the part you actually need depends on a number you probably haven’t looked for since the toilet was installed. How to find your toilet model number comes down to checking three specific spots inside the tank in the right order – most homeowners never look past the first one, and that’s usually enough. Get the number wrong, or grab the water-use rating instead of the model number by mistake, and you’ve ordered the wrong flapper, fill valve, or seal.

This guide walks through exactly where Kohler, TOTO, American Standard, Mansfield, and store-brand toilets hide their tank number, how to read the date stamp when the model number is gone, and what to do when nothing on the toilet is legible at all.

Quick answer – where is my toilet’s model number? Remove the tank lid and look at the inside back wall of the tank, usually near or just above the waterline. That’s where most manufacturers stamp, mold, or print the tank model number – the number that determines most of your repair parts. If it’s not there, check the underside of the tank lid next, then the bowl itself.

How to Find Your Toilet Model Number: Start Inside the Tank

Lift the tank lid straight up and set it on a towel – porcelain chips easily, and the lid is one of the more expensive single parts to replace. Look at the inside back wall, and for TOTO toilets also check the right-hand wall opposite the trip lever.

Kohler’s identification guide treats a two-piece toilet as three separately marked parts: a tank model number, a bowl model number, and a lid part number, each in a different location Kohler identification guide. TOTO model numbers are stamped or engraved directly into the porcelain, usually on the back wall and sometimes on the right-hand wall, and typically combine letters with a three-digit number PlumbingSupply Toto parts finder. American Standard tanks often carry a printed inside-tank label – a Home Depot listing for an American Standard Champion 4 tank shows the label reading 4149A alongside the flush rating and a date stamp, all on the same interior surface Home Depot American Standard Champion 4 tank.

Don’t confuse the flush-volume rating with the model number – they’re printed close together and homeowners mix them up constantly. 4149A is the model; 1.28 gpf next to it is only the water-use rating, not an identifier Saving Water Partnership. If the stamp is hard to read through mineral buildup, wipe the wall with a cloth and shine a flashlight across it at an angle rather than straight on – the raking light catches the depressions in the porcelain.

Check the Underside of the Tank Lid Next

If the tank wall is blank, worn smooth, or covered by an insulating liner, flip the lid over and look at the underside. Korky’s identification diagram marks the underside of the tank lid as a common label location, alongside the inside back wall for the tank number and the front exterior of the tank for the brand name Korky identification diagram.

One catch: a lid number usually identifies the lid, not the whole toilet. Kohler’s guide treats the lid part number as its own separate identifier from the toilet or tank model number Kohler identification guide. That’s genuinely useful if you need to replace a cracked or mismatched lid, but it won’t always get you to the right internal repair parts. Photograph whatever you find under the lid before setting it back down – if you end up calling a manufacturer or parts retailer, a lid number plus photos of the flush valve mechanism can help them work backward to the original model.

Check the Bowl if the Tank Number Doesn’t Match

On a two-piece toilet, the tank and bowl can technically be different model lines if a previous owner swapped one half during an earlier repair – so it’s worth checking both, especially before ordering a seat, a bowl-specific gasket, or a full replacement fixture. Kohler’s diagram calls out the bowl model number as a distinct identifier from the tank number, found on the bowl itself rather than inside the tank Kohler identification guide.

For most day-to-day repairs – a flapper, a fill valve, a flush valve – the tank number is the one that matters, since Mansfield’s parts workflow (and most manufacturers’) starts from the tank model number to find compatible parts Mansfield model number guide. Treat the bowl number as a backup when the tank is unmarked, or as a requirement when you’re ordering something bowl-specific.

No Model Number Visible? Use the Date Stamp Instead

Toilets don’t carry a faucet-style serial number – there’s no rotating code that pins down a production batch the way there is on a faucet cartridge. What toilets do carry, in roughly the same spots as the model number, is a manufacture date stamp, and it’s the next best clue when the model number is gone Saving Water Partnership.

Date stamps typically appear on the tank’s back wall or the underside of the lid, often near the model number, and are commonly formatted as month-day-year with a two-digit year – a stamp reading 4 5 87 means April 5, 1987 Saving Water Partnership. Paired with the gallons-per-flush (gpf) rating, a date narrows down the toilet’s generation even without a legible model number: pre-1982 toilets commonly used 5-7 gpf, 1982-1992 toilets commonly used 3.5 gpf, 1993-present toilets commonly use 1.6 gpf, 2004-present models may use 1.28 gpf, and 2014-present models may use 1.1 gpf or less Saving Water Partnership.

That generation window matters for one more reason: TOTO’s “Eco” versions can share the same base model number as a non-Eco version but add an E suffix, and the only real difference is flush volume – commonly 1.6 gpf versus 1.28 gpf – which can change which flush valve or flapper actually fits PlumbingSupply Toto guide. A date stamp and gpf rating help you catch that distinction even when the model number itself looks identical.

How to Find Your Toilet Model Number by Brand

Once you know where to look, brand-specific format cues confirm you’re reading the right thing:

Brand	First place to look	Model format	Best lookup path
Kohler	Inside tank for the tank number; bowl for the bowl number; lid underside for the lid part number Kohler identification guide	Commonly a K- style product number Kohler parts diagram guide	Search the model number on Kohler.com, then use the interactive Parts & Support diagram Kohler parts diagram guide
TOTO	Inside back wall, and the right-hand wall opposite the trip lever PlumbingSupply Toto guide	Letters plus a three-digit number; color code starts with # plus two digits, e.g. #01 Cotton White, #11 Colonial White PlumbingSupply Toto guide	Use the model number, not the marketing line name, with a picture-based parts reference PlumbingSupply Toto guide
American Standard	Inside-tank printed label near the waterline Home Depot American Standard tank	Four-digit tank number such as 4149A, often next to a gpf/lpf rating and date stamp Home Depot American Standard tank	American Standard’s Toilet Parts collection and Replacement Part Service Guide American Standard toilet parts
Mansfield	Inside the tank, underside of the lid, or underside of the tank itself Mansfield model number guide	Numeric tank model number Mansfield model number guide	Select the tank number from Mansfield’s model listing Mansfield model number guide
Glacier Bay / store brands	Tank label or stamp, cross-checked against the retailer’s product page Home Depot American Standard tank example	Varies – retailer SKU and model number both matter	Retailer product page (Home Depot) plus a universal parts finder Korky identification diagram

Manufacturer Lookup Tools

Once you’ve narrowed how to find your toilet model number down to a specific string of letters and digits, each major manufacturer has its own lookup path for turning that number into an actual parts list.

Kohler. Search the model number on Kohler.com, open the product’s Parts & Support section, and use the interactive parts diagram, which lets you click blue part numbers to see the name, part number, and price Kohler parts diagram guide. The tool only works once you already have a correct model number, which is why the tank check above comes first.

American Standard. The Toilet Parts collection covers replacement flush valves, trip levers, dual-flush seals, fill valves, and tank-coupling kits, and the main site links out to a Toilet Replacement Part Service Guide American Standard toilet parts. Because the catalog is broad, cross-check your tank label rather than guessing from a photo alone.

TOTO. TOTO USA’s own site can be blocked by bot checks in some lookup tools, so PlumbingSupply’s picture-based Toto reference is a practical workaround – click through toilet images to reach the matching parts schematic, and prioritize the model number over the marketing line name, since TOTO has renamed lines while keeping the underlying model number the same PlumbingSupply Toto guide.

Mansfield. Mansfield’s dedicated model-number guide has you find the tank number first, then select it from a listing to see compatible parts Mansfield model number guide. A missing or unreadable tank number here usually means photo comparison or a call to Mansfield support.

Korky / universal lookup. For common 2-inch gravity toilets, Korky’s universal kit lists compatible model groups across American Standard, Gerber, Glacier Bay, Kohler, Mansfield, and TOTO without requiring an exact model match Korky identification diagram. It won’t help with a canister, dual-flush tower, or pressure-assist system, where an exact model still matters.

Once you’ve got a number to search, our free Repair Finder can help match it to the correct replacement part instead of guessing off the shelf.

What to Do If You Still Can’t Find the Model Number

Before you take anything apart, build a photo set: the tank’s front logo, the interior back wall, the right-hand wall, the underside of the lid, the flush valve, the fill valve, the trip-lever side, the bowl shape, the area between the seat bolts, and any date or gpf stamp – these are the same spots identified across Korky, Mansfield, TOTO, and Saving Water Partnership’s guidance Korky identification diagram Mansfield model number guide PlumbingSupply Toto guide. InspectAPedia’s toilet manufacturer directory is a useful next stop when only a logo, trademark, or stamp style survives InspectAPedia toilet manufacturers.

For a common failure – a worn flapper or a failing fill valve – a universal kit sized to the flush-valve opening (2-inch or 3-inch) is a reasonable fallback once you’ve measured, since flush valves are generally sold in those two sizes and the replacement needs to match the existing opening The Spruce flush valve types. Universal parts are not a fallback for a Kohler-style canister, a TOTO Eco flush valve, an American Standard Champion tower, or a pressure-assist vessel – those need a model-matched part.

Replacing the whole toilet becomes the more sensible option once the model is truly unidentifiable, the toilet uses an obsolete proprietary mechanism, or the tank or bowl itself is cracked. The Spruce reports toilet installation commonly runs $240 to $695 and averages around $470, with plumber labor running $75 to $150 per hour on top of that The Spruce toilet installation cost – context worth weighing before you spend another weekend chasing an unmarked part.

When to Call a Plumber for Identification

Call a plumber when identification would require disassembly, when the toilet has a sealed pressure-assist vessel, or when the tank-to-bowl connection is already leaking. The Spruce specifically flags overflowing toilets and clogs that won’t clear with a plunger or auger as call-a-plumber situations, not DIY-identification situations The Spruce common toilet problems. Pressure-assisted toilets use a sealed internal vessel that’s a meaningfully different repair than a standard gravity-flapper tank The Spruce pressure-assisted toilets.

A 30-minute identification visit can be cheaper than two or three wrong parts orders, especially on a TOTO Eco variant or an American Standard tank with several similar-looking flush valves in the parts catalog American Standard toilet parts. The Spruce reports plumber rates from $75 to $150 per hour for installation-adjacent work, and separately an average plumber hourly cost of $105 for repairs with a $35-$170 range depending on location The Spruce toilet installation cost The Spruce plumber cost. Budget for a minimum trip or diagnostic fee on top of the hourly rate – a 2026 MarketWatch consumer column describes a $160 diagnostic fee charged for a single toilet cistern issue, which is a useful reminder that a “quick look” isn’t always priced by the half-hour MarketWatch plumber diagnostic fee.

Quick Reference: What You Found and What to Do Next

What you found	What it means	Next step
A clear tank number inside the tank	Your primary identifier – most repair parts are matched to this	Search the manufacturer’s parts tool or our Repair Finder
Only a bowl number	Good for bowl-specific parts (seat, rim gasket)	Use it for bowl orders; keep checking for the tank number for other repairs
Only a lid part number	Identifies the lid, not the whole toilet	Order the lid directly; use photos for anything else
A date stamp but no model number	Narrows the toilet’s generation and likely gpf rating	Combine with brand logo and visual cues, or call the manufacturer
Nothing legible, brand logo visible	Use brand-specific cues, then a manufacturer photo/parts tool	Contact manufacturer support with your photo set
Nothing legible at all	Treat as unidentified	Try universal parts for common repairs, or weigh replacement

What to Do Next

Once you have a model number, our companion guide covers the fuller identification workflow – including flush-valve sizing and rough-in measurements for a replacement – in How to Identify Your Toilet Brand and Model. If your next question is why the toilet is acting up in the first place, see Why Is My Toilet Running? 6 Common Causes. Bookmark the Toilet Repair Guide (Pillar 2 hub) as the index for the rest of this cluster as new identification and repair guides publish.

Sources

• Kohler: Identifying Your Toilet Model
• Kohler: Troubleshooting and Identifying Product Replacement Parts
• American Standard: Toilet Parts Collection
• Mansfield: Toilet Model Number Guide
• Korky: 2-Inch Universal Complete Repair Kit
• PlumbingSupply: TOTO Toilets Parts Finder and FAQ
• InspectAPedia: Toilet Manufacturers and Parts Sources
• Home Depot: American Standard Champion 4 Tank
• Saving Water Partnership: How Much Water Does Your Toilet Use
• The Spruce: Toilet Flush Valve Types
• The Spruce: Repairing Common Toilet Problems
• The Spruce: Best Pressure-Assisted Toilets
• The Spruce: Toilet Installation Cost
• The Spruce: How Much Does a Plumber Cost
• MarketWatch: Plumber Diagnostic Fee Column

Educational content only. Not a substitute for licensed professional advice. Local plumbing codes vary by jurisdiction. Use of any guidance from this guide is at your own risk.

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