TOTO Toilet Parts: OEM vs Aftermarket and Where to Buy

Why TOTO Parts Sourcing Matters More Than It Does for Other Brands

TOTO has been manufacturing toilets since 1917 and sells more bathroom fixtures in Japan than any other brand. In North America, the Drake series (CST744SL / CST744EL) and the UltraMax II (MS604114CEFG) together represent the majority of the brand's installed base, so the parts ecosystem for those models is mature. For newer lines like the Aquia IV dual-flush or the Nexus compact elongated, parts availability is more limited and OEM sourcing is especially important.

Understanding which parts are interchangeable with universal aftermarket components -- and which are brand-specific assemblies -- saves money without compromising performance. This guide covers every major part category, maps OEM versus aftermarket viability, lists authorized sources, and flags common mistakes homeowners and plumbers make when ordering TOTO replacement parts.

What Are the Main Replaceable Parts Inside a TOTO Toilet?

Breaking down the full parts list helps clarify where aftermarket options are safe and where they are not:

Fill Valves

TOTO uses a float-cup-style fill valve on most of its two-piece models. The Drake and Drake II both ship with the TOTO TSU99A.X fill valve assembly. This part is readily available through TOTO's authorized parts program. Aftermarket alternatives from Fluidmaster (the 400A and 400AH) and Korky (Model 528 series) are mechanically compatible with the Drake's 2-inch shank and standard 7/8-inch locknut. Both Fluidmaster and Korky are EPA WaterSense-compliant components and do not affect flush certification for the bowl itself, since the bowl's WaterSense rating is based on trapway geometry, not fill valve brand. Aggregated owner reviews on Amazon and Home Depot indicate that both aftermarket fill valves are accepted without modification by the vast majority of Drake and Drake II owners.

Flappers and Flush Valves

This is the most critical area of differentiation between two-piece and one-piece TOTO toilets.

Two-piece models (Drake, Drake II, Eco Drake, Entrada) use a 3-inch flapper on models built after approximately 2007. The TOTO THU175 is the OEM flapper. Korky's 3-inch red silicone flapper (model 2030BP) and Fluidmaster's model 5403 are both widely cited by plumbers as compatible alternatives. Silicone flappers outlast rubber flappers in chloraminated municipal water by a factor of three to five, which matters in markets like Phoenix, Las Vegas, and much of the Southeast where chloramine disinfection is standard. Rubber flappers typically last 3 to 5 years in these systems; silicone typically lasts 10 or more.

One-piece models (UltraMax II, Carlyle II, Soiree, Nexus, Vespin II) use a tower-style canister flush valve assembly. The canister seal inside the tower is the most commonly replaced sub-component. TOTO sells the replacement seal separately as the THU808 (for most one-piece models built after 2011). Aftermarket canister seals exist from Danco and other suppliers, but fit can be inconsistent, and owner reviews reveal a higher rate of incompatibility compared to OEM. The safest approach for one-piece tower-valve maintenance is to use the OEM seal unless a specific aftermarket part has confirmed compatibility for your model number.

Trip Levers and Handles

Trip levers are primarily aesthetic components, but they must match the tank's side hole (left-hand or right-hand) and the chain attachment point. TOTO sells trip levers in cotton white (01), sedona beige (12), colonial white (11), and bone (03) finishes. Universal chrome or brushed nickel handles are widely available and generally fit TOTO tanks with the standard 5/16-inch nut, but color matching to TOTO's proprietary palette requires OEM or TOTO-licensed parts. The TOTO THU030S trip lever is a common replacement for two-piece models.

Tank-to-Bowl Gaskets and Bolts

The tank-to-bowl gasket is a high-wear part in humid climates. TOTO's original gasket (part THU141) is a sponge-foam type. Universal sponge gaskets in the same diameter are widely compatible. Standard 5/16-inch stainless-steel brass tank bolts from any plumbing supplier fit TOTO two-piece models.

Wax Rings

TOTO toilets have the same 4-inch horn as any standard residential toilet. Universal wax rings from Harvey's, Fernco, or Danco are fully compatible. Wax-free options like the Fernco Wax Free Ring are also compatible and popular for floor-level installations where repeated reinstalls are anticipated.

OEM vs Aftermarket: Which Parts Are Safe to Swap?

Where Can You Buy Genuine TOTO Replacement Parts?

TOTO Direct (us.totousa.com)

TOTO's U.S. website has a dedicated parts and accessories section organized by model series. This is the most reliable source for OEM part numbers, model compatibility charts, and installation documentation. Shipping times are typically 3 to 7 business days for standard parts. TOTO also operates a parts support line that can cross-reference a toilet's serial number (stamped inside the tank) to confirm which parts apply.

Authorized Plumbing Distributors

Ferguson Enterprises, F.W. Webb, Hajoca, and Winsupply all carry TOTO as an authorized brand. Distributor pricing is generally lower than MSRP for the same OEM part, and these suppliers often stock less common parts that are not available at big-box retailers. Counter staff at these locations typically have access to TOTO's parts catalog and can pull exact replacements by model number. This channel is especially useful for WASHLET electronic components, Tornado Flush rim assemblies, and discontinued model parts.

Home Depot and Lowes

Both retailers carry common TOTO parts such as the THU175 flapper, TSU99A fill valve, and THU030S trip lever in-store or available for order. Stock varies significantly by location, and availability is concentrated on the most popular models (Drake, UltraMax II). For less common parts, in-store purchasing often requires a special order, which adds 5 to 10 days of lead time. That said, both retailers are convenient for emergency same-day repairs on mainstream models.

Amazon

Amazon lists both genuine TOTO parts and compatible aftermarket alternatives. The key to safe purchasing is filtering for items "sold by TOTO" or "fulfilled by Amazon" with an authorized seller verification. TOTO genuine parts on Amazon are typically priced comparably to TOTO's own eStore. For aftermarket alternatives like the Korky 2030BP flapper or Fluidmaster 400AH fill valve, Amazon is highly competitive on price and ships quickly via Prime. Aggregated reviews on these aftermarket listings are a useful signal for Drake and UltraMax II compatibility, with many reviewers confirming specific model fits in question-and-answer sections.

Browse TOTO fill valves and replacement parts: Check prices on Amazon

Specialty Online Plumbing Retailers

Sites like PlumbersStock, SupplyHouse.com, and ToyletParts.com specialize in replacement parts and tend to have deeper inventory for TOTO's full product line including discontinued and older-generation models. SupplyHouse.com in particular carries TOTO parts alongside brands like Kohler, American Standard, Gerber, and Woodbridge, making it useful for multi-brand repair projects. These specialty sites often provide parts diagrams and exploded-view drawings that make it easier to identify the correct sub-component before ordering.

How Do TOTO Parts Compare to Kohler and American Standard Parts Availability?

American Standard's Champion 4 and Cadet 3 use a fully proprietary PowerWash rim system but standard flappers and fill valves that Fluidmaster and Korky both cover with confirmed-compatible parts. Kohler's Highline and Cimarron use 3.25-inch canister flush valves that require Kohler-specific replacements but are widely available through any plumbing supply house. Woodbridge uses standard tank internals similar to American Standard, making aftermarket sourcing straightforward for most of their models.

TOTO falls between these extremes. The brand's two-piece Drake line is accessible through standard aftermarket channels for flappers and fill valves. The one-piece and integrated WASHLET lines require OEM sourcing, which narrows the purchasing channel but still allows online ordering through TOTO's eStore with reasonable shipping times. For homeowners choosing between brands with long-term ownership cost in mind, this parts access difference is a real consideration -- though TOTO's documented durability means owners generally replace parts less frequently than comparable American Standard or Kohler installations. For more context on how these brands compare, see our full best flushing toilets guide.

What Are the Most Common TOTO Repair Issues and the Parts That Fix Them?

Running Toilet

A running toilet on a Drake or Drake II is almost always caused by a degraded flapper that no longer seats tightly against the flush valve seat. The TOTO THU175 (OEM) or Korky 2030BP (aftermarket) resolves this in the vast majority of cases. If the flapper is intact, the fill valve may be allowing water to siphon past the overflow tube, in which case replacing the fill valve with a TOTO TSU99A or aftermarket equivalent corrects the issue. The food-coloring dye test (add dye to the tank, do not flush, and observe whether color appears in the bowl within 15 minutes) confirms a flapper leak before purchasing parts.

Ghost Flushing

Ghost flushing -- where the toilet briefly refills on its own without being flushed -- is a symptom of water leaking from the tank into the bowl. On two-piece TOTO models, the flapper is the usual culprit. On one-piece models, the canister seal (THU808) degrades over time and allows a slow drip that eventually triggers the fill valve. Replacing the seal typically resolves ghost flushing on UltraMax II and Carlyle II models without requiring full tank disassembly.

Weak Flush

A weak flush on a TOTO Tornado Flush model is rarely a parts failure. The Tornado Flush system uses two angled rim ports to create a cyclonic water flow rather than the traditional rim holes found on most American-made toilets. These ports can accumulate calcium and mineral deposits over time, particularly in hard-water markets, which reduces cyclone intensity and can drop flush performance below the originally certified MaP level. Cleaning the ports with a wire brush or dental pick and a diluted muriatic acid or CLR solution restores performance in most cases. If performance does not recover after cleaning, the flush valve itself may have a partial blockage and TOTO's support line should be consulted. For step-by-step guidance, see our article on how to improve toilet flush power.

WASHLET Not Working

WASHLET malfunctions -- no warm water, nozzle not extending, loss of heating function -- are electronic or mechanical issues that require TOTO-specific diagnosis and OEM parts. TOTO's WASHLET warranty covers most electronic components for one year (bidet seat) and the water supply system for five years. Out-of-warranty WASHLET repairs should go through TOTO's service network rather than a general plumber, since the diagnostic codes are model-specific and parts are not sold through standard retail channels. For an overview of available WASHLET models, our TOTO WASHLET reviews detail the C100, C200, S500e, and S550e feature sets.

TOTO Model-Specific Parts Reference

TOTO Drake (CST744SL / CST744EL)

The Drake is TOTO's best-selling two-piece toilet in North America. It uses G-Max 1.6 GPF flushing, which the MaP testing program rates at 1,000 grams (the maximum test load). The Drake uses the TSU99A fill valve, THU175 flapper (3-inch), and THU030S trip lever. The tank model is ST744E. All three internal components have confirmed aftermarket equivalents. Parts are available at Home Depot, Lowes, and Amazon in major markets. For a detailed product breakdown, see our TOTO Drake review.

TOTO Drake II (CST454CEFG / CST454CUFG)

The Drake II upgraded to Tornado Flush 1.28 GPF flushing with a wider 3-inch flush valve for improved efficiency. It carries EPA WaterSense certification. The fill valve is the TSU99A, flapper is the THU175 (same as Drake), and trip lever is the THU030S. The lower GPF means fill volume is less, so the fill valve cycle is slightly shorter. Owner reviews confirm Korky and Fluidmaster aftermarket fill valves are fully compatible.

TOTO UltraMax II (MS604114CEFG)

The UltraMax II is TOTO's flagship one-piece elongated model with Tornado Flush 1.28 GPF and integrated SoftClose seat. It uses a tower-style canister flush valve; the canister seal is the THU808. There is no standard flapper. The fill valve is integral to the tower assembly for this model, so fill-valve repairs typically involve replacing the entire tower module or the canister seal only. The UltraMax II does not accept standard aftermarket flappers. MaP score is 1,000 grams. See the UltraMax II review for full performance data.

TOTO Aquia IV (MS446124CEMFG / CT446FG)

The Aquia IV is a dual-flush toilet (1.28 / 0.9 GPF) with Tornado Flush technology and WASHLET+ compatibility. Its dual-flush activation requires a proprietary dual-flush trip lever assembly. The fill valve is a specialized low-profile unit designed for the Aquia IV's compact tank. Aftermarket compatibility is limited; sourcing directly from TOTO or an authorized distributor is recommended. The Aquia IV holds EPA WaterSense certification for both flush volumes and MaP certification at 1,000 grams on the full flush.

TOTO Neorest (NX1 / 750H)

The Neorest line represents TOTO's highest-tier integrated smart toilet. The Neorest 750H uses a 1.0/0.8 GPF dual-flush system with ewater+ electrolyzed water self-cleaning, automatic open/close lid, heated seat, air deodorizer, and WASHLET wand. Every internal component -- from the flush valve to the electronic control board -- is OEM-only. Neorest repairs should go through TOTO's authorized service network. The Neorest 750H carries EPA WaterSense certification and achieves MaP 1,000 grams on the full flush. These units fall outside typical DIY repair and are serviced under TOTO's premium warranty program.

TOTO Warranty Coverage and How Parts Affect It

TOTO's standard limited warranty covers the toilet (vitreous china) for one year on residential installations against manufacturing defects. Mechanical parts (fill valve, flush valve, trip lever) carry a one-year warranty. WASHLET seats carry a one-year parts warranty and a five-year warranty on the water supply components.

Installing aftermarket parts does not automatically void TOTO's warranty on the toilet itself (the bowl and tank ceramic). However, TOTO can decline warranty service on the specific mechanical assembly if a non-OEM part caused the failure. For example, if a third-party canister seal degrades and the resulting water hammer damages the tower flush valve, TOTO may decline warranty replacement of the tower valve while still honoring a separate claim on the ceramic. This is a meaningful distinction: the bowl is unlikely to crack from a parts choice, so the practical warranty risk from aftermarket flappers and fill valves is low for two-piece models.

For WASHLET seats, TOTO is explicit that unauthorized service or non-OEM parts void the electrical component warranty. This is standard across the smart toilet industry and applies equally to Kohler's Veil intelligent toilet, American Standard's Spalet, and other integrated electronic seats.

For a detailed breakdown of how TOTO's warranty compares to competitors, see our toilet warranty comparison guide.