Fill valves are the most replaceable internal toilet component — and for most residential toilets, they are effectively universal. One Fluidmaster 400A or Korky 528 fits the majority of gravity-flush toilets sold in North America without any adaptation. But three conditions break that universality: tank height outside the fill valve’s adjustable range, pressure-assist toilet systems that use a sealed pressure vessel instead of an open fill valve, and TOTO’s proprietary fill system used on some of their tower-flush designs. Knowing which side of that line your toilet sits on takes 30 seconds.
This guide is for homeowners replacing a running, leaking, or failed fill valve. It identifies every condition that changes compatibility, explains the adjustable height range that makes most fill valves work across tanks, and gives a clear decision for each toilet type.
Universal fill valves ship at a mid-height setting. If the fill valve is installed without adjusting to match the tank depth, the water level will be too high (water runs into the overflow tube) or too low (weak flush). After installing any fill valve, set the water level to 1 inch below the top of the overflow tube. This single adjustment step is skipped in most amateur installs and causes the most post-installation running toilet complaints.
What Makes a Fill Valve Universal — and What Breaks That Universality
Fill valve universality is built on two design decisions: a standard 7/8-inch shank diameter that fits the water inlet hole at the bottom of every residential toilet tank, and an adjustable body height that telescopes to fit tanks of different depths. These two features cover the vast majority of residential gravity-flush toilets regardless of brand, age, or flush volume.
The 7/8-inch shank is the industry-wide standard connection size for residential toilet fill valves in North America. Every major fill valve manufacturer — Fluidmaster, Korky, Danco, and Watts — produces fill valves with a 7/8-inch shank. Every major toilet manufacturer — TOTO, Kohler, American Standard, Mansfield, and Gerber — installs a 7/8-inch inlet in their tank bottom. Brand does not affect connection size. This is genuinely universal across the residential market.
The adjustable height range is where universality has limits. Standard fill valves adjust from approximately 7.5 to 13.5 inches in total height. Tanks that are deeper than 13.5 inches (uncommon but present in some older low-profile tank designs) require a tall fill valve. Tanks shallower than 7.5 inches (found in some wall-hung toilet carrier systems) require a compact fill valve. For standard residential two-piece and one-piece toilets, the 7.5–13.5-inch adjustable range covers every tank without a specialty product.
Are Toilet Fill Valves Universal by Tank Height?
Tank height — the inside depth of the tank from bottom to the water level line — is the one fill valve dimension that occasionally requires a non-standard product. Measure the inside depth of your tank before purchasing a fill valve if the tank appears unusually shallow or deep.
If your tank inside depth measures 7.5–13.5 inches, any standard adjustable fill valve fits. This range covers the overwhelming majority of residential toilets, including all standard two-piece designs from TOTO, Kohler, American Standard, Mansfield, and Gerber. Fluidmaster 400A (adjusts 9–14 inches), Korky 528 (adjusts 8–14 inches), and Danco (adjusts 9–14 inches) are the three most installed universal fill valves in North America.
If your tank inside depth is shallower than 7.5 inches, you need a compact or short fill valve. Fluidmaster’s 400LS (low profile) and Korky’s 528T are designed for compact tanks with 6.5–9.5-inch depths. These appear in some wall-hung toilet tanks, certain slim-profile one-piece designs, and some European toilet designs that use narrow tanks.
If your tank is unusually deep — over 14 inches inside depth — a tall fill valve is needed. Fluidmaster’s 400AH (high performance) extends to 16 inches. These deep tanks appear primarily in older low-profile and close-coupled toilet designs from the 1960s–1980s, and in some commercial-grade residential toilets designed for reduced flush noise through greater tank depth.
Are Toilet Fill Valves All the Same Size? Connection and Float Types
Beyond height, fill valves differ in float type — the mechanism that senses when the tank is full and shuts off the water supply. Float type does not affect compatibility with the tank, but it affects installation ease and long-term performance.
Side-float fill valves (ballcock style) use a horizontal float arm with a float ball that rises as the tank fills and shuts the valve when it reaches the set water level. These were the residential standard for most of the 20th century. They are adjustable by bending the float arm or by a screw on the fill valve body. Ballcock-style fill valves are still sold and work correctly in any standard tank — but they are bulkier, more prone to float-arm corrosion, and take more skill to adjust precisely.
Vertical-float fill valves (tower or column style) use a float that slides up and down the fill valve body itself. These are the current professional standard — Fluidmaster 400A uses a side-float/arm configuration while Fluidmaster’s 400A replacement and Korky’s 528 use a tower-float design. Tower-float fill valves are more compact, easier to adjust, less prone to the rocking and corrosion that affects ballcock float arms, and the correct choice for any new fill valve installation. See our full buying guide for the best toilet fill valves for current model recommendations across tank configurations.
Fill valve shank connection size — the 7/8-inch shank that threads through the tank bottom — is uniform across all residential fill valve types, both ballcock and tower styles. Connection size never changes which fill valve you can use. Height range and float type are the only variables that affect selection.
Pressure-assist toilets — including Kohler Pressure Lite, American Standard Pressure Assist, and Sloan Flushmate-equipped models — use a sealed pressure vessel inside the tank rather than an open fill valve and flapper system. The pressure vessel charges under incoming water pressure and releases it in a pressurized burst during the flush. A standard fill valve cannot be installed in a pressure-assist toilet because the tank has no standard flapper or fill valve configuration — it houses only the pressure vessel and its supply connection. Pressure vessel replacement requires the Flushmate cartridge specific to your toilet model.
Fill Valves for Pressure-Assist and Dual-Flush Toilets
Two toilet types do not use standard fill valves — and identifying whether you have one of them is the most important pre-purchase step for fill valve replacement.
Pressure-assist toilets use a Flushmate or equivalent pressure vessel. The tank on a pressure-assist toilet looks like a standard tank from outside, but inside there is a sealed plastic vessel that fills with pressurized water from the supply line. There is no open water surface in the tank — no flapper, no standard fill valve, and no float ball. To identify a pressure-assist toilet: open the tank lid and look inside. If you see a sealed plastic vessel (usually white or gray) rather than open water, you have a pressure-assist toilet. Replacement requires the Flushmate model-specific cartridge at $60–$120.
Dual-flush toilets with tower-style flush valves do use a standard fill valve — but the fill valve must account for the dual-flush tower mechanism in the tank. Most dual-flush towers are designed around standard 7/8-inch fill valve connections, and a standard fill valve installs normally. The dual-flush mechanism is the flush valve (flapper equivalent), not the fill valve. After a dual-flush replacement flapper or tower cartridge, the fill valve is unaffected. Standard fill valves are compatible with dual-flush gravity toilets.
TOTO toilets — including the Drake II, UltraMax II, and Aquia IV — use standard 7/8-inch fill valve connections and accept universal fill valve replacements. TOTO’s G-Max and E-Max flush systems are gravity-flush designs that do not require proprietary fill valves. The TOTO WASHLET+ integrated toilet seat, however, has an integrated water supply connection that bypasses the fill valve — replacing a WASHLET+ fill valve requires confirming the supply routing before purchasing.
What Competitor Guides Don’t Tell You About Fill Valve Universality
Standard fill valves are rated for 20–80 PSI inlet water pressure. At pressures above 80 PSI — common in homes near water tower supply lines or in multi-story buildings with unregulated pressure — fill valves cycle rapidly, wear out in 1–2 years, and sometimes produce a high-pitched whining sound during tank fill. At pressures below 20 PSI — common in rural areas with low-pressure wells — fill valves fill slowly and may not fully shut off, causing a slow run. If you are replacing fill valves repeatedly at shorter-than-expected intervals, check water pressure with a gauge at the toilet shut-off valve. Fluidmaster’s 400AH is rated for higher pressure ranges and is the correct choice for high-pressure supply situations.
Fill valve water level and overflow tube height work together. The overflow tube sets the maximum safe water level — water above the overflow tube drains continuously into the bowl, causing a running toilet. The fill valve’s float adjustment sets the target fill level. The correct fill level is 1 inch below the top of the overflow tube. If you replace a fill valve without measuring the existing overflow tube height and setting the float accordingly, the odds of a running toilet after installation are high. Before purchasing any fill valve, note the overflow tube height in your tank. Standard overflow tubes are 9–11 inches tall in most residential tanks — well within the fill valve’s adjustable range.
Fill valve noise during tank refill varies by design, and the difference is audible through bathroom walls. Ballcock-style fill valves produce the loudest refill sound — water turbulence in the open tank creates noise that carries. Tower-style fill valves with anti-siphon refill tubes direct water quietly into the overflow tube and are significantly quieter. Fluidmaster’s 400A is among the quieter standard fill valves. Korky’s QuietFILL Platinum is the quietest standard residential fill valve currently in production — specifically designed for bedrooms and master baths where tank refill noise is a real concern. Noise is not a compatibility issue, but it is the most common reason homeowners replace a recently installed fill valve.
If your toilet is a standard gravity-flush two-piece or one-piece model from any major brand with a tank inside depth between 7.5 and 13.5 inches — and it is not a pressure-assist design — any standard adjustable fill valve is universal for your toilet. In that configuration, which describes the vast majority of residential toilets installed in North America, Fluidmaster 400A and Korky 528 both work without modification. The tank height, shank connection, and float mechanism are all compatible. The only required step is adjusting the float height after installation to set the water level 1 inch below the overflow tube. The conditions that break universality are specific and identifiable in 30 seconds by looking inside the tank.
Decision Matrix: Are Toilet Fill Valves Universal for Your Toilet?
| Your Toilet Type | Tank Type | Tank Depth | Fill Valve to Buy |
|---|---|---|---|
| Standard gravity-flush, any major brand | Open water tank | 7.5–13.5 in | Fluidmaster 400A or Korky 528 ✓ |
| Compact or wall-hung tank | Open water tank | Under 7.5 in | Fluidmaster 400LS or Korky 528T ✓ |
| Older low-profile tank | Open water tank | Over 14 in | Fluidmaster 400AH (tall fill valve) ⚠ |
| Dual-flush gravity toilet | Open water, tower flush | Standard range | Standard fill valve — compatible ✓ |
| Pressure-assist toilet (Flushmate) | Sealed pressure vessel | N/A | Flushmate pressure cartridge — no fill valve ⛔ |
| Noisy bathroom / master bath | Open water tank | Standard range | Korky QuietFILL Platinum ✓ |
Frequently Asked Questions
Are toilet fill valves universal?
Yes — for standard gravity-flush toilets with open water tanks, fill valves are effectively universal. Every major residential toilet brand uses a standard 7/8-inch tank inlet, and adjustable fill valves cover the tank depth range of virtually all residential designs. Universality breaks down for pressure-assist toilets (sealed pressure vessel, no fill valve), compact wall-hung tanks shallower than 7.5 inches (require low-profile valves), and unusually deep tanks over 14 inches (require tall fill valves). Identify which side of this line your toilet is on before purchasing.
Are toilet fill valves all the same size?
The shank connection size — the 7/8-inch threaded shank that secures through the tank bottom — is the same across all residential fill valves. Height varies, but adjustable fill valves cover the 7.5–13.5-inch range that fits nearly all residential tanks. Fill valves sold for residential use in North America are dimensionally interchangeable at the connection point — the brand name on the valve does not affect whether it connects to the tank inlet.
How do I know if my fill valve needs replacing?
Three symptoms indicate a failing fill valve: (1) Running water sound that continues more than 90 seconds after the flush cycle — the fill valve is either failing to shut off or set too high. (2) Slow tank fill — more than 3 minutes to refill after a full flush suggests a clogged fill valve screen or a failing diaphragm seal. (3) Intermittent running in the middle of the night (phantom flush) — often caused by the fill valve slowly leaking enough water that the water level drops below the float shutoff point. In all three cases, a fill valve replacement at $8–$18 is the correct repair.
Can I replace my toilet fill valve myself?
Yes — fill valve replacement is one of the most DIY-accessible plumbing repairs. The process: turn off the water supply at the shut-off valve, flush the toilet to empty the tank, disconnect the supply line from the tank bottom, unscrew the fill valve locknut from below the tank, lift out the old valve, insert the new valve, adjust height to set the float stop 1 inch below the overflow tube, reconnect the supply line, and turn water back on. Total time: 15–25 minutes with basic tools. No soldering, no pipe cutting, no experience beyond tightening a locknut by hand.
What is the best fill valve brand?
Fluidmaster 400A is the highest-volume fill valve in North American residential plumbing — installed in more toilets than any other model. Korky 528 and QuietFILL Platinum are the leading alternatives, with QuietFILL offering noticeably lower fill noise for bedrooms and master baths. Danco is a budget option that performs adequately in low-pressure supply situations. For toilets with water pressure above 60 PSI, Fluidmaster’s 400AH or Korky’s 528BP are the more durable choices. Brand matters more for longevity under high pressure than for compatibility — all major brands are compatible with standard tanks.
How long does a toilet fill valve last?
In normal water pressure conditions (30–60 PSI) with chlorinated municipal water, a quality fill valve lasts 5–8 years. In high-pressure conditions (above 70 PSI), fill valves wear the diaphragm seal faster and typically need replacement every 3–5 years. In chloramine-treated water, standard rubber diaphragms degrade faster — chloramine-resistant fill valves extend service life in treated water. A fill valve that needs replacement every 2 years is signaling high water pressure or aggressive water chemistry, not a product defect. See our guide on diagnosing running toilet problems for a full diagnostic of fill valve vs. flapper as the failure source.
Do TOTO toilets need a special fill valve?
No — TOTO gravity-flush toilets sold in North America (Drake, Drake II, UltraMax, UltraMax II, Entrada, Aquia IV, and related models) use standard 7/8-inch fill valve connections and accept Fluidmaster 400A, Korky 528, and other universal fill valves without modification. TOTO’s proprietary components are the flush valve (tower cartridge) and the washlet seat electronics — not the fill valve. TOTO’s tower flush system does not affect fill valve compatibility. Replace with any standard adjustable fill valve of the correct height range.
If you have a standard gravity-flush toilet with an open water tank — yes, fill valves are universal. Buy Fluidmaster 400A or Korky 528, adjust height after installation, and set float level 1 inch below the overflow tube. Brand does not matter beyond noise preference and pressure rating.
If you have a pressure-assist toilet — no fill valve replacement applies. Open the tank and confirm whether you see open water or a sealed pressure vessel. If sealed vessel, purchase a Flushmate model-specific pressure cartridge — not a fill valve.
If you have high water pressure (above 70 PSI) or a compact tank — standard fill valves technically fit but underperform. High pressure requires a pressure-rated fill valve (Fluidmaster 400AH). Compact tanks under 7.5 inches require a low-profile fill valve (Fluidmaster 400LS). Measure tank depth and check supply pressure before purchasing.
Are Toilet Fill Valves Universal Across Kohler, American Standard, and TOTO?
Across all three major brands — and every other major North American toilet manufacturer — fill valve compatibility is determined by tank inlet size and tank depth, not brand. Kohler tanks accept Fluidmaster and Korky fill valves identically to how they accept OEM Kohler fill valves. American Standard tanks work the same way. TOTO gravity-flush tanks, as noted, accept standard fill valves without any brand-specific adapter.
OEM fill valves from toilet manufacturers are almost always rebranded Fluidmaster or Korky products sold at a premium. A Kohler-branded fill valve in the $25–$35 range is typically a Fluidmaster 400A variant with Kohler packaging and a slightly higher margin. For most homeowners, purchasing a Fluidmaster 400A at $8–$12 produces the same result as purchasing the OEM fill valve at two to three times the price.
The one exception to cross-brand fill valve universality: some Sloan commercial flush valve systems and some Moen residential toilets use proprietary fill mechanisms that require brand-specific parts. These are the minority of residential installations. If the toilet brand is not one of the major five residential brands — TOTO, Kohler, American Standard, Mansfield, Gerber — confirm fill valve compatibility with the manufacturer before assuming standard fill valve universality. For more on what components are and are not standardized across toilet brands, see our guides on are toilet flappers universal and are toilet tanks interchangeable.
Are Toilet Fill Valves All the Same Size for 1.28 GPF WaterSense Toilets?
WaterSense-certified 1.28 GPF toilets use the same 7/8-inch fill valve connection as all other residential toilets — fill valve universality is not affected by the toilet’s flush volume certification. The distinction for WaterSense toilets is in the flapper or flush valve, which is calibrated to release exactly 1.28 gallons per flush. The fill valve refills the tank to the set water level regardless of what that level is — it does not control flush volume.
One practical consideration for 1.28 GPF toilets: the tank water level may be set lower than in older 1.6 GPF toilets, because less water is needed per flush. After installing a universal fill valve in a WaterSense toilet, set the float stop to the manufacturer’s marked fill line inside the tank — not to 1 inch below the overflow tube if that mark is lower. Many 1.28 GPF toilets have a fill line indicator on the overflow tube or tank interior wall that represents the engineered water volume. Following that mark rather than the generic 1-inch-below-overflow rule preserves the toilet’s WaterSense performance.
For a comprehensive look at fill valve selection, installation, and brand-specific recommendations, see our dedicated guide on the best toilet fill valves. The question of whether are toilet fill valves universal resolves quickly for most homeowners — standard gravity-flush toilet, standard tank depth, standard brand — universal fill valve, adjust height, done.
When to Replace the Fill Valve vs. When to Replace the Whole Toilet
A fill valve replacement makes sense when the toilet is otherwise in good condition — bowl intact, flapper sealing correctly, flange and wax ring sound, no cracks in the tank or bowl. In that case, an $8–$18 fill valve and 20 minutes of work solves the problem for another 5–8 years. The fill valve is not the expensive component — it is the easiest and cheapest component to replace in the entire toilet assembly.
Fill valve replacement does not make sense when the toilet is over 20 years old with a 3.5 GPF or higher flush volume, when the bowl has surface crazing or a cracked vitreous china body, or when the fill valve failure is the third or fourth repair on the same toilet in a short period. In those cases, the toilet itself is the problem — not the individual components. A WaterSense toilet at 1.28 GPF saves $50–$100 per year in water costs compared to a 3.5 GPF toilet, meaning a $400 installed replacement pays back in water savings in 4–8 years.
For homeowners deciding between repair and replacement, our guide to the best toilets of 2026 covers the models with the best long-term value at every price point. Fill valves are universal enough that the replacement decision is almost never about finding the right part — it is about whether the toilet is worth the repair at all.
