Best toilet repair kit for a running toilet: Fluidmaster and Korky fill valve and flapper kits compared by height range, flapper size and what the box contains
Maker pages compared: Fluidmaster 400H kits adjust 9 to 14 in, Korky 528MP kits 8-1/2 to 14 in; measure the old flapper, 3 in across means a 2 in flapper.
- Verified
- Updated
- 11 min read
- 16 sources
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OwnerSpec compares published manufacturer specifications, certification listings and sourced technical documents. Unless a page explicitly states otherwise, OwnerSpec has not laboratory-tested or used the products it compares. Editorial policy
Short answer
The best toilet repair kit depends on two measurements, not on the toilet brand. For a 2 in flush valve the pick is the Fluidmaster K-400H-039: its guide pairs the PerforMAX 400H fill valve, which Fluidmaster’s product page rates at 9 to 14 in of adjustment and 1.28 to 3.5 gpf, with a 502 Universal 2 in flapper. For a 3 in flush valve the pick is the Korky 830MP: Korky’s page pairs the QuietFILL Platinum 528MP, adjustable from 8-1/2 to 14 in, with the 3060 large 3 in flapper. Measure the old flapper end to end: 3 in across means a 2 in flapper, 4 in across means a 3 in flapper, per Fluidmaster’s sizing rule. If you cannot tell, the Fluidmaster K-400H-043-T4 ships one flapper that adjusts to both. Skip every kit if the leak test names the refill tube or chain, and skip the Korky 5010MP complete kit on any Kohler or one-piece toilet, because Korky says so.
The picks
Old flapper measures 3 in across and the fill valve is tired too
Fluidmaster K-400H-039 PerforMAX fill valve and 2 in flapper kit
Fluidmaster's K-400H-039 guide: PerforMAX fill valve plus a 502 Universal 2 in flapper with its dial preset to 9; the 400H page gives the valve 9 to 14 in of adjustment and 1.28 to 3.5 gpf
Cannot tell whether the flush valve is 2 in or 3 in
Fluidmaster K-400H-043-T4 PerforMAX fill valve and 2 in / 3 in Super Flapper kit
Fluidmaster's kit page and guide: one adjustable flapper for 2 in (red guide) and 3 in (blue guide) flush valves, anti-siphon fill valve, 1.28 to 3.5 gpf, fits most 2 and 3 in flush valve toilets including Kohler, American Standard and TOTO
3 in flush valve, or an overflow tube under 9 in
Korky 830MP QuietFILL Platinum fill valve and large 3 in flapper kit
Korky's 830MP page: 528MP fill valve adjusting 8-1/2 to 14 in, 3060 large 3 in flapper for HET toilets since 2000, refill tube with metal clip, refill adjuster; ASSE and UPC marks shown without a standard number
3 in tank with a pitted flush valve seat, not Kohler, not one-piece
Korky 5010MP QuietFILL Platinum large 3 in complete toilet repair kit
Korky's 5010MP page: 528MP fill valve, 3060 3 in flapper, 5030 flush valve, 3 bolts, 3 rubber washers, 3 metal washers, 3 nuts; Korky states it does NOT fit Kohler toilets or 1-piece toilets
2 in tank leaking at the tank-to-bowl gasket or the flush valve seat
Korky 4010X 2X Long Life standard 2 in complete toilet repair kit
Korky's 4010X page: 528X fill valve, 2017 flapper, adjustable 2 in flush valve with tank-to-bowl gasket, 3 bolts, washers and nuts; brand list includes Kohler, American Standard and TOTO; 10-year warranty; made in USA
If the toilet runs because the refill tube sits down the overflow pipe or the chain is too short, no kit on this page fixes it: run the 10-minute dye test first, because it names the part before you spend anything.
How was this shortlist built?
A fill valve refills the tank; a flapper is the hinged rubber disc that seals the flush valve at the tank floor; a complete kit adds the flush valve itself plus the tank-to-bowl bolts and gasket.
OwnerSpec compared the maker pages and installation guides for Fluidmaster’s 400H, K-400H-039, K-400H-043 and 400AKR and Korky’s 830MP, 818MP, 5010MP and 4010X, read on 10 October 2026, on five points: fill valve adjustment range, flapper size, box contents, certification wording as printed, and the toilets each maker says the kit fits. Nothing was installed or flushed.
Two kits are missing on purpose. Danco’s site refused every request, so no Danco or Next by Danco kit is compared. Fluidmaster’s 400AKRP10 listing is not on Fluidmaster’s instruction index, so this page cites the 400AKR guide and leaves that listing out.
The numbers below agree with the fill valve by model page and the 2 in versus 3 in flapper page: a Kohler canister or an American Standard Champion takes a seal, not a flapper, and fits none of these kits.
How do the kits compare on paper?
Every figure is the maker’s published one. “Not printed” means the page does not state it.
| Kit | Fill valve and adjustment range | Flapper size | What the box contains, per the maker | Certification wording as printed | Fits, per the maker |
|---|---|---|---|---|---|
| Fluidmaster K-400H-039 | PerforMAX 400H, 9 to 14 in (400H page) | 2 in | Fill valve, 502 Universal flapper preset to 9, refill tube | “CSA certified and code-approved” (400H page) | 2 in and 3 in flush valve toilets, 1.28 to 3.5 gpf (400H page) |
| Fluidmaster K-400H-043-T4 | PerforMAX fill valve, range not printed on the kit page (400H: 9 to 14 in) | 2 in or 3 in, one adjustable flapper | Fill valve, Super Flapper, hardware, guide | “Anti-siphon valve” (kit page) | Most 2 and 3 in flush valve toilets including Kohler, American Standard and TOTO, 1.28 to 3.5 gpf |
| Fluidmaster 400AKR (guide only) | 400A-style valve, range not printed; C.L. mark 1 in above the overflow pipe | Adjustable flapper preset to #9; 2 in or 3 in not stated in the guide | Tank lever, flush valve with tank-to-bowl gasket, fill valve, flapper | Not printed in the guide | 3.5 gpf or larger toilets may need a 501 or 504 flapper instead |
| Korky 830MP | QuietFILL Platinum 528MP, 8-1/2 to 14 in | 3 in (3060) | Fill valve, 3060 flapper, refill tube and metal clip, hardware, refill adjuster | “UPC and ASSE” marks, no number | HET toilets since 2000: American Standard, AquaSource, Briggs, Crane, Delta, Eljer, Gerber, Glacier Bay, Kohler, Mansfield, TOTO and more |
| Korky 818MP | QuietFILL Platinum 528MP, 8-1/2 to 14 in | 2 in (100, adjusts 1.28 to 5 gpf) | Fill valve, 100 flapper, refill tube and clip, hardware | “CUPC and ASSE” marks, no number | “99% of toilets” |
| Korky 5010MP | QuietFILL Platinum 528MP, 8-1/2 to 14 in | 3 in (3060) | Fill valve, 3060 flapper, 5030 flush valve, 3 bolts, 3 rubber washers, 3 metal washers, 3 nuts | “CUPC and ASSE” marks, no number | American Standard, TOTO, Mansfield, Eljer, Gerber, Glacier Bay; “does NOT fit Kohler toilets”, “does NOT fit 1-piece toilets” |
| Korky 4010X | 2X Long Life 528X, 8-1/2 to 14 in | 2 in (2017) | Fill valve, 2017 flapper, adjustable flush valve and tank-to-bowl gasket, 3 bolts, washers, 3 nuts | “CUPC and ASSE” marks, no number | American Standard Cadet I and II, Calais, Colony; Briggs, Eljer, Gerber, Glacier Bay, Kohler, Mansfield, Seasons, TOTO |
No page opened for either maker prints a standard number next to its certification mark, so this page prints none. Fluidmaster’s K-400H guides put the cap about 3 in above the top of the overflow pipe, the water level 1/2 in below it, and the overflow top at least 1 in below the tank lever hole.
Fluidmaster K-400H-039: buy it or skip it?
Buy it if the old flapper measures 3 in across and the fill valve is old enough to replace at the same time. Fluidmaster’s guide pairs the PerforMAX fill valve with a 502 Universal 2 in flapper, its dial preset to 9, and the 400H page gives the valve 9 to 14 in of adjustment and a 7-year limited warranty.
The flaw is the floor of that range. An overflow tube under 9 in is outside the 400H’s printed adjustment, and the Korky 528MP reaches 8-1/2 in; measure before ordering.
Skip it if the flapper measures 4 in across: that is a 3 in flush valve, and the Korky 830MP is the matching kit. If only the flapper has failed, a single Korky 100 is the smaller purchase.
Fluidmaster K-400H-043-T4: buy it or skip it?
Buy it if you cannot tell which flush valve the tank has. Fluidmaster’s kit page describes one adjustable flapper for 2 in and 3 in flush valves rated 1.28 to 3.5 gpf, and its install guide says a 2 in flapper fits the red sizing guide on the packaging and a 3 in flapper the blue one. The page names an anti-siphon valve and lists Kohler, American Standard and TOTO among the toilets it fits.
The flaw is that the kit page prints no height range in inches. The 9 to 14 in figure on this page is from the 400H product page and applies because the kit’s valve is the PerforMAX.
Skip it if you already measured a 3 in flapper on a Kohler Class Five tank: the flapper page shows Kohler’s catalog calls that size 3-1/4 in and lists its own GP1078441, and the Korky 3060 is the aftermarket part that names those Kohler numbers.
Korky 830MP: buy it or skip it?
Buy it if the old flapper measures 4 in across, or if the overflow tube sits below 9 in. Korky’s page pairs the QuietFILL Platinum 528MP, adjustable from 8-1/2 to 14 in, with the 3060 large 3 in flapper, a refill tube with a metal clip and a refill adjuster, and lists American Standard, Gerber, Glacier Bay, Kohler, Mansfield and TOTO among the HET toilets since 2000 it fits.
The flaw is that the 3060 is a flapper, and Korky’s own 5010MP page excludes Kohler toilets outright. Lift the lid: a tall cylinder in the middle of the tank is a canister seal, and no flapper kit fits it.
Skip it if the 2 in flapper is the right size: the Korky 528MP is sold alone and the 818MP is the same valve with a 2 in flapper.
Korky 5010MP: buy it or skip it?
Buy it if the flush valve seat itself is pitted or the tank leaks at the tank-to-bowl gasket on a 3 in tank. Korky’s page lists the 528MP fill valve, the 3060 flapper, the 5030 flush valve, 3 bolts, 3 rubber washers, 3 metal washers and 3 nuts, and says the flapper adjusts for toilets made after 2000.
The flaw is written on the box by the maker: “The 5010 kit does NOT fit Kohler toilets” and “Does NOT fit 1-piece toilets”. Korky lists American Standard, TOTO, Mansfield, Eljer, Gerber and Glacier Bay as fits.
Skip it if the leak test named only the flapper or the fill valve: replacing a flush valve means lifting the tank off the bowl, and the 830MP needs no such step.
Korky 4010X: buy it or skip it?
Buy it if the tank is a 2 in flush valve with a failed gasket or seat and you want the longest printed warranty here. Korky’s page lists the 528X fill valve, the 2017 flapper, an adjustable flush valve with tank-to-bowl gasket, 3 bolts, rubber and metal washers and 3 nuts, a 10-year warranty and a fit list that includes Kohler, American Standard Cadet I and II, Briggs, Eljer, Gerber, Glacier Bay, Mansfield and TOTO.
The flaw is that Korky’s Platinum 2 in complete kit, the 4010MP, could not be read from the maker this session, so the 4010X is the only 2 in complete kit on this page and its 528X valve is the 2X Long Life, not the QuietFILL Platinum.
Skip it if the toilet is old enough that a new toilet is the better spend: the best toilet page sorts current models by maker spec sheet, and the rough-in page shows the one measurement that decides whether a replacement fits.
Measure twice, then buy one kit
Do not order a kit until you have two numbers: the old flapper end to end (3 in across is a 2 in flapper, 4 in across is a 3 in flapper, per Fluidmaster) and the overflow tube height from the tank floor (9 to 14 in for the Fluidmaster 400H, 8-1/2 to 14 in for the Korky 528MP). If the dye test showed no color in the bowl and the tank still refills on its own, the Fluidmaster 400H alone replaces the part that failed and the flapper stays.
Who should skip every kit?
The refill tube reader. Fluidmaster’s K-400H guides clip the refill tube to the rim of the overflow pipe; a tube pushed down inside it keeps the toilet running with every part in good order. Lift it and re-clip it.
The chain reader. A chain with no slack holds the flapper off its seat. Re-hook it before buying anything.
The seal reader. A Kohler canister or an American Standard Champion tower has no flapper, and the flapper page lists the seal part numbers instead.
The clog reader. A toilet that will not clear is a different problem: see the plunger versus auger guide.
What goes wrong?
The wrong flapper size. A 2 in flapper on a 3 in seat never seals. Korky’s 3060 page dates 3 in flush valves to toilets installed since 2005, and Fluidmaster’s 400AKR guide warns that a 3.5 gpf or larger toilet may need its 501 Harsh Water or 504 all-rubber flapper instead of the kit flapper.
Over-tightening. Fluidmaster’s guides say to hand-tighten the locknut and the supply connector only.
Drop-in cleaners. Fluidmaster’s 400H page rules out bleach or chlorine drop-in cleaners in the tank. A flapper replaced twice in a year on a tank that uses them is the cleaner, not the flapper.
The water level set wrong. Both makers put the finished water level 1/2 in below the top of the overflow pipe. Higher, and the tank trickles into the overflow and runs again with new parts.
Frequently asked questions
Do I need a complete kit or just a flapper?
Run the dye test first. Color in the bowl after 10 minutes names the flapper, and a single Korky 100 or Fluidmaster 502 fixes that. A tank that refills on its own with no color in the bowl, or a valve that never shuts off, names the fill valve. A complete kit with a flush valve is for a pitted seat or a leaking tank-to-bowl gasket.
How do I know if my toilet takes a 2 inch or 3 inch flapper?
Measure the old flapper end to end. Fluidmaster's sizing rule is 3 inches across for a 2 inch flapper and 4 inches across for a 3 inch flapper. Korky's 3060 page says its 3 inch flapper is designed for 3 inch flush valves installed since 2005. If you cannot measure, the Fluidmaster K-400H-043-T4 kit ships one flapper that adjusts to either size.
Which fill valve fits a short toilet tank?
Korky's QuietFILL Platinum 528MP adjusts from 8-1/2 to 14 inches, and the Fluidmaster 400H from 9 to 14 inches, so an overflow tube that sits below 9 inches needs the Korky valve and therefore a Korky kit: the 830MP for a 3 inch flapper or the 818MP for a 2 inch flapper. Measure the overflow tube from the tank floor before ordering.
Does a Korky complete kit fit a Kohler toilet?
Korky's 5010MP page states in its own words that the kit does not fit Kohler toilets and does not fit one-piece toilets. Korky's 4010X page, the 2 inch complete kit, lists Kohler in its fit list alongside American Standard, Briggs, Eljer, Gerber, Mansfield and TOTO. A Kohler canister tank takes a seal, not a flapper, so no flapper kit fits it.
Are these kits anti-siphon or ASSE certified?
Fluidmaster's 400H page says CSA certified and code-approved, and its kit pages name an anti-siphon valve; no Fluidmaster page opened prints a standard number. Korky's kit pages show ASSE and UPC or cUPC marks, again without a number. This page therefore names the certifier each maker names and prints no standard number for either brand.
Fact sheet and how to cite this page
- Answer
- For a 2 in flush valve the kit is the Fluidmaster K-400H-039 (400H fill valve, 9 to 14 in, 502 2 in flapper); for a 3 in flush valve the Korky 830MP (528MP fill valve, 8-1/2 to 14 in, 3060 flapper). Only the Korky 5010MP and 4010X complete kits replace the flush valve, and Korky says the 5010MP does not fit Kohler or one-piece toilets.
- Comparison basis
- Fluidmaster’s 400H product page, K-400H-043 kit page and the K-400H-043, K-400H-039 and 400AKR installation guides; Korky’s 830MP, 818MP, 5010MP and 4010X kit pages and its 3060 and 100TP flapper pages, compared on fill valve adjustment range, flapper size, kit contents, the certification wording each maker prints and the toilets each maker says the kit fits.
- Assumptions
- The leak test in the running toilet guide has already named the flapper, the fill valve or both as the failed part; a refill tube or chain fault needs no kit
- The tank has a flapper on a 2 in or 3 in flush valve, not a Kohler canister seal or an American Standard Champion tower seal
- The overflow tube height falls inside the fill valve’s printed range: 9 to 14 in for the Fluidmaster 400H, 8-1/2 to 14 in for the Korky 528MP
- Method
- OwnerSpec compared manufacturer-published specifications read on 2026-10-10 and confirmed each listing in stock the same day; it did not install, flush or run any kit, and reports only the figures the cited Fluidmaster and Korky documents state. Danco’s site refused every request, so Danco kits are not compared.
- Primary source
- Fluidmaster, 400H PerforMAX Fill Valve product page (manufacturer or vendor document)
- Facts verified
- Last updated
- Cite as
- OwnerSpec, "Best toilet repair kit for a running toilet: Fluidmaster and Korky fill valve and flapper kits compared by height range, flapper size and what the box contains", https://ownerspec.com/plumbing/reviews/best-toilet-repair-kit-fill-valve-and-flapper/, facts verified 10 October 2026.
Every figure above also appears, with its source, in the article. All sources ยท How OwnerSpec verifies numbers
Sources
- Fluidmaster, 400H PerforMAX Fill Valve product page (manufacturer or vendor document)
- Fluidmaster, K-400H-043-T4 fill valve and 2 in / 3 in Super Flapper kit page (manufacturer or vendor document)
- Fluidmaster, K-400H-043 Quick Install Guide (PDF) (manufacturer or vendor document)
- Fluidmaster, K-400H-039 PerforMAX Fill Valve and 2 in Flapper Quick Install Guide (PDF) (manufacturer or vendor document)
- Fluidmaster, 400AKR Complete Toilet Repair Kit installation instructions (PDF) (manufacturer or vendor document)
- Fluidmaster, Determining Whether You Have a 2 or 3 inch Flush Valve and Flapper (manufacturer or vendor document)
- Fluidmaster, Installation Instructions index (manufacturer or vendor document)
- Fluidmaster, PerforMAX high-performance toilet repair kit with tools page (manufacturer or vendor document)
- Fluidmaster, 523A-009-T4 Universal 2 in / 3 in Super Flapper page (manufacturer or vendor document)
- Korky, QuietFILL Platinum Fill Valve and Large 3 in Flapper Kit 830MP (manufacturer or vendor document)
- Korky, QuietFILL Platinum Fill Valve and 2 in Flapper Kit 818MP (manufacturer or vendor document)
- Korky, QuietFILL Platinum Large 3 in Complete Toilet Repair Kit 5010MP (manufacturer or vendor document)
- Korky, 2X Long Life Standard 2 in Universal Complete Toilet Repair Kit 4010X (manufacturer or vendor document)
- Korky, Toilet Repair Kits index (manufacturer or vendor document)
- Korky, Large 3 in Premium Universal Flapper 3060 (manufacturer or vendor document)
- Korky, 2 in Ultra High Performance Flapper 3-Pack 100TP (manufacturer or vendor document)