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Quick answer from a licensed plumber: TOTO’s parts manuals name a fill valve per model: TSU708 on the Drake and Entrada, TSU54A (flapper) or TSU53A (tower) on the Drake II CST454, TSU83.30-A on the newer Drake II MS454 tanks, TSU51A on the Ultramax II and TSU99A.X on the Aquia II. TOTO’s own parts store now lists just one universal fill valve, the TSU99A.XR, plus model-specific valves for the Maris, Connelly and in-wall tanks. Do TOTO’s overnight leak test first; a level that does not drop points at the fill valve. (American Standard’s version of the test is in our American Standard fill valve guide.)
Top pick: TOTO Adjustable Replacement Fill Valve Assembly — the Amazon listing says it is adjustable for all TOTO toilet tanks (Amazon-sold on September 24, 2026).
Step 1: Prove It Is the Fill Valve
TOTO’s FAQ says most toilets have “only four components that may need to be replaced if the toilet doesn’t shut off: The flapper The flush valve The fill valve The trip lever,” and it gives a “no tools needed” test to tell them apart: “Allow the tank to fill, then close the water supply at the shutoff valve. Mark the water level inside the tank, and let sit overnight. If the water level drops, it is either a problem with the flapper or with the flush valve.”
The fill valve is the suspect when the level does not move: “If the water in Step 1 did not drop at all, the problem is most likely with the fill valve.” TOTO lists the confirming symptoms: water “going over the top of the overflow tube on the flush valve,” hissing or dripping “from the end of refill tube into the overflow tube,” or a tank that is “not filling the tank at all, or is filling in erratic starts and stops.” For that last one TOTO says debris may be in the valve, and “cleaning the fill valve may eliminate the symptom.”
Step 2: Find the Tank Model Number
TOTO’s parts manuals are organized by model, and the fill valve part number changes with the tank. The TOTO Parts Store has a “How to identify toilet model” button that opens its video “Identifying Your TOTO Toilet Model Number.” On a two-piece toilet the tank has its own number (for example the newer Drake II parts manual PD-01354 lists tanks ST454EA and ST454ER for the MS454124CEF(R)(G) and Washlet+ MW454 models), and the store lists its model-specific fill valves by tank number (Maris ST484, Connelly ST494).
Step 3: Match the Part Number
These are the fill valves TOTO’s own parts manuals name for common models. The manuals we read are linked in the sources; the part sits in the tank drawing with the description shown here.
| TOTO model (parts manual) | Fill valve in the manual | Note |
|---|---|---|
| Drake CST744S / CST744SG (PD-00242) | TSU708 “Fill Valve for Flapper Type” | Tower-type tanks in the same manual use the TSU01D drain valve instead of a flapper |
| Drake CST744E / CST744EG (PD-00131) | TSU708 “Fill Valve” | |
| Entrada CST244EF / CST244EFR (PD-00757) | TSU708 “Fill Valve” | |
| Drake II CST454CEF / CST454CEFG (PD-00126) | TSU54A “Fill Valve for Flapper Type”; TSU53A “Fill Valve for Tower Type” | Look in the tank: a flapper on a chain or a tower (drain valve) |
| Drake II MS454124CEF(R)(G) and Washlet+ MW454 models (PD-01354) | TSU83.30-A “Fill Valve for Flapper Type” | Tanks ST454EA / ST454ER |
| Ultramax II MS604114CEF / MS604114CEFG (PD-00640) | TSU51A “Fill Valve” | Tower-type drain valve |
| Aquia II CST416M (PD-00191) | TSU99A.X “Fill Valve” | Dual-flush; the manual notes items used with the THU435 and THU224 flush valves |
The TOTO Parts Store’s “Flush & Fill Valves” category, read on September 24, 2026, lists only five fill valves: the TSU99A.XR “UNIVERSAL FILL VALVE ASSEMBLY,” the TSU42A “FILL VALVE FOR MARIS ST484,” the TSU46AR and TSU47AR for in-wall tanks (the TSU47AR for the WT171M), and the TSU83-A “FILL VALVE CONNELLY ST494.” The manual-specific numbers above (TSU708, TSU54A, TSU53A, TSU51A, TSU99A.X, TSU83.30-A) are not in that store list. So for a Drake, Drake II, Entrada, Ultramax II or Aquia II, the part TOTO itself now sells for the job is the TSU99A.XR universal, and the Amazon listing for TOTO’s adjustable fill valve says it is “Adjustable for all TOTO toilet tanks.”
I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.
Step 4: Set the Water Level and Chain
A new valve is only half the fix if the settings are wrong. TOTO’s FAQ: “The water level in the tank should be about ½ inch below the top of the overflow tube. The chain on the flapper should only have 1 or 2 links of slack and the black refill tube from the fill valve, should be flowing water into the overflow tube during the refill.” TOTO adds that a weak flush, or one that only works every other time, can be “Incorrect settings or worn out toilet parts,” naming “A worn out flapper, fill valve, trip lever or flush valve.”
Erratic Flushing
If the flush itself is erratic rather than the fill, TOTO points at the handle: “Erratic flushing may also occur if the trip lever is wearing out. Replacement should solve the problem.” The trip lever for the Supreme, Ultimate, Ultramax and Carolina tanks (ST701, CST854, CST884) is the THU808 on the store list, and other tanks have their own; check the store by tank number.
FAQ
What fill valve does a TOTO Drake use?
TOTO’s parts manuals list the TSU708 fill valve for the Drake CST744S/SG and CST744E/EG. That number is not in the TOTO Parts Store’s current fill valve list; the store sells the TSU99A.XR universal fill valve assembly, and TOTO’s listing says its adjustable valve fits all TOTO tanks.
What fill valve does a TOTO Drake II use?
The Drake II CST454CEF/CEFG manual lists the TSU54A for flapper-type tanks and the TSU53A for tower-type tanks; the newer MS454124CEF and Washlet+ MW454 manual lists the TSU83.30-A. Look in the tank to see whether it has a flapper or a tower.
Is the TOTO TSU99A.XR a universal fill valve?
Yes. The TOTO Parts Store lists it as the UNIVERSAL FILL VALVE ASSEMBLY, and the Amazon listing for TOTO’s adjustable fill valve says it is adjustable for all TOTO toilet tanks with a standard 7/8-inch inlet.
How do I know whether the fill valve or the flapper is the problem?
TOTO’s test: fill the tank, shut the supply valve, mark the level and leave it overnight. If the level drops, the flapper or flush valve is leaking. If it does not drop, the fill valve is the likely problem, especially if water runs over the overflow tube or the valve hisses.
How high should the water be in a TOTO tank?
TOTO says about half an inch below the top of the overflow tube, with one or two links of slack in the flapper chain and the refill tube flowing into the overflow tube while the tank fills.
Why Trust Plumbing Picks
Plumbing Picks is written by a licensed Georgia journeyman plumber. Every part number, model list, size, setting and fit on this page comes from the manufacturer pages and documents listed below, which we opened and read; product details come from those makers and from the Amazon listings, not from hands-on testing. Each linked product was shipped or sold by Amazon, new and in stock, when we checked on September 24, 2026. Where a link goes to Amazon we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.
Sources
- TOTO USA: Product FAQ (leak test, replacement parts, water level)
- TOTO Parts Store: Flush & Fill Valves
- TOTO Parts Store (all parts)
- TOTO parts manual PD-00242: Drake CST744S / CST744SG
- TOTO parts manual PD-00131: Drake CST744E / CST744EG
- TOTO parts manual PD-00757: Entrada CST244EF / CST244EFR
- TOTO parts manual PD-00126: Drake II CST454CEF / CST454CEFG
- TOTO parts manual PD-01354: Drake II MS454124CEF(R)(G) and Washlet+ MW454 models
- TOTO parts manual PD-00640: Ultramax II MS604114CEF / MS604114CEFG
- TOTO parts manual PD-00191: Aquia II CST416M
Bottom Line
Run the overnight test, read the tank number, then check the table. Unless you have a Maris, Connelly or in-wall tank, the part TOTO sells today is the TSU99A.XR universal, and the Amazon listing says it fits every TOTO tank. Set the level half an inch below the overflow tube and give the chain one or two links of slack.