Fluidmaster 400H PerforMAX Toilet Tank Flapper Repair Kit is the best toilet repair kit for a slow fill because it tackles the tank-side wear that keeps refill speed dragging after a flush. If your toilet is a TOTO or Kohler and you want a brand-matched repair path, the dedicated TOTO TSU01R Fill Valve Replacement Kit or KOHLER K-46320 Fill Valve Service Kit fits better.
The cleanest buy leaves fewer loose parts to sort, bag, and store. That matters in a small bathroom, where a bag of extra seals turns into clutter fast. A kit that fixes the complaint without adding hardware clutter wins this category.
Quick Picks
| Pick | Repair scope | Best fit | Listed numeric detail | Main trade-off |
|---|---|---|---|---|
| Fluidmaster 400H PerforMAX Toilet Tank Flapper Repair Kit | Flapper and fill-side refresh | Most slow-fill complaints in standard tanks | Not listed | More parts to sort |
| Korky 528MP 2-in. Toilet Fill Valve Repair Kit | Fill valve replacement | Lower-cost refill fix | 2-in. | Flapper stays untouched |
| TOTO TSU01R Fill Valve Replacement Kit | Fill valve replacement | TOTO tanks | Not listed | Narrow compatibility |
| Danco 10705 Toilet Fill Valve Repair Kit | Fill valve replacement | Fast DIY swap | Not listed | Generic fit needs checking |
| KOHLER K-46320 Fill Valve Service Kit | Fill valve service kit | Kohler tanks | Not listed | Not a universal answer |
Fast read: the smaller the repair scope, the less cleanup and storage hassle you deal with. The broader kit handles more wear points, but it also puts more pieces on the sink counter.
Who This Guide Is For
This guide fits homeowners who open the tank lid, see a slow refill after flushing, and want a kit instead of a parts scavenger hunt. It fits first-time buyers who want one clear path from diagnosis to checkout, with fewer leftover pieces and less second-guessing.
It also fits buyers who care about reordering later. A matched repair path beats a random mix of washers, seals, and adapters when the same toilet stays in the house for years.
What We Looked For
The ranking leans on repair scope first. A fill-valve-only kit solves a narrow problem cleanly, while a broader kit earns its place when the tank needs more than one worn part replaced.
Compatibility sits right behind that. TOTO and Kohler toilets reward exact-match parts, and generic kits demand more checking before you click buy.
Cleanup and storage mattered too. A kit with fewer loose pieces leaves less mess during the repair and less hardware to label, bag, and stash afterward.
Parts ecosystem also mattered. A repair kit that points to a clear replacement path beats a loose bundle of generic extras when the toilet needs attention again later.
1. Fluidmaster 400H PerforMAX Toilet Tank Flapper Repair Kit: Best Overall
Fluidmaster 400H PerforMAX Toilet Tank Flapper Repair Kit leads because it covers more of the common slow-fill complaint without forcing a full toilet replacement. The appeal is simple: when the tank needs a broader refresh, a flapper-plus-tank-side repair path solves more of the wear pattern in one shot.
The trade-off is parts count. More coverage brings more pieces to sort, and that matters if the goal is the fastest one-part swap in a cramped bathroom. This is not the pick when the toilet only needs a fill valve and the rest of the tank hardware looks healthy.
Buy this for a standard slow-fill toilet where the tank parts look tired and the buyer wants the strongest all-around shot at stopping repeat trips to the store. Skip it when the fix is clearly isolated to one valve or when brand-specific parts are the safer route.
2. Korky 528MP 2-in. Toilet Fill Valve Repair Kit: Best Value
Korky 528MP 2-in. Toilet Fill Valve Repair Kit is the value play because it goes straight after the part that controls refill speed. That keeps the repair focused, which is the right move when the flapper still seals and the tank’s slow refill points at the valve.
The catch is scope. Saving money here means leaving the flapper and other tank parts alone, so this kit does not solve a broader tank refresh. If the tank has more than one worn component, the cheaper route stops short.
This is the right buy for a budget-minded homeowner who wants the refill fixed with the fewest new parts possible. It is the wrong buy for a toilet that needs a brand-match repair or a more complete tank reset.
3. TOTO TSU01R Fill Valve Replacement Kit: Best Specialist Pick
TOTO TSU01R Fill Valve Replacement Kit earns its spot because TOTO toilets reward parts that match the tank system instead of forcing a generic fit. That brand-specific path removes guesswork, which matters when the slow-fill issue sits inside a toilet built around its own parts map.
The limitation is obvious. This kit belongs with TOTO tanks, not every toilet on the shelf. If the toilet is not a TOTO model, a generic fill-valve kit gives you a wider lane.
Buy this when the toilet is a TOTO and you want the replacement path to line up with the original design. Pass on it when the toilet brand is different or when you need a broader repair that includes more than the fill valve.
4. Danco 10705 Toilet Fill Valve Repair Kit: Best Simple Pick
Danco 10705 Toilet Fill Valve Repair Kit makes sense when the job is plain: the tank refills slowly, the fill valve is the obvious culprit, and speed matters more than brand specificity. It keeps the repair simple and keeps the parts bag from getting crowded.
The compromise is compatibility checking. A generic kit asks you to verify the tank layout and connection style before ordering, and that extra step matters in tighter or proprietary tanks. It also does nothing for a worn flapper that needs replacement at the same time.
This is the best fit for a quick DIY turnaround on a standard tank. It is not the right call for a TOTO or Kohler toilet that wants a matched parts path.
5. KOHLER K-46320 Fill Valve Service Kit: Best Premium Pick
KOHLER K-46320 Fill Valve Service Kit belongs on the list because Kohler toilets do better with the right service kit than with a generic part that asks the buyer to force a fit. The branded route cuts down on uncertainty and gives the repair a cleaner match to the tank setup.
The trade-off is narrow usefulness. This kit pays off inside a Kohler tank, and it stops being the right answer outside that brand family. That makes it more specialized than the top overall pick.
Choose it when the toilet is a Kohler and the repair should follow Kohler’s parts path. Skip it when the tank is generic or when the slow fill is only one piece of a bigger tank overhaul.
How to Narrow the List
The complaint pattern decides the winner faster than the label does. Slow fill is not one problem, and the right kit depends on whether the tank needs one valve, a broader refresh, or a brand-specific part match.
| What the toilet does | Best match | Why this pick wins | Skip it if |
|---|---|---|---|
| Tank refills slowly, flapper shows wear | Fluidmaster 400H | Refreshes more than one tank-side wear point | You want the fastest single-part swap |
| Slow refill, flapper still seals | Korky 528MP | Narrow budget fix with less parts hunting | The toilet is TOTO or Kohler and needs a brand match |
| TOTO tank, brand diagram matches | TOTO TSU01R | Brand-matched path trims guesswork | The toilet is a generic tank |
| Need the fastest straight swap | Danco 10705 | Simple valve replacement | You want a broader tank refresh |
| Kohler tank, service-kit route | KOHLER K-46320 | Brand-specific service path | The toilet is not Kohler |
The cleanest path also leaves the cleanest workspace. A narrow valve swap creates less clutter on the counter, and that matters when the repair happens in a tight bathroom with nowhere to stage extra parts.
Who Should Look Elsewhere
This list stops at the toilet tank. If the slow fill starts upstream, the kit is the wrong buy.
Look elsewhere when the shutoff valve is partly closed, the supply line is kinked, or the water issue traces back to the plumbing at the wall. A toilet kit does not fix those problems. It also misses cracked tanks, broken supply hardware, and any repair that belongs outside the tank itself.
If the toilet already has a proprietary fill system and the brand does not appear in the kit name, stop and match the exact replacement path first. Guessing here turns a simple repair into a return.
What to Check on the Product Page
The product page should tell you three things fast: what part gets replaced, what toilet it fits, and how much hardware you need to store afterward.
| Listing clue | What it tells you | Storage and cleanup note |
|---|---|---|
| “Fill valve replacement kit” | Narrow repair scope | Fewer loose parts on the counter |
| “Flapper repair kit” | Broader tank refresh | More pieces to sort and bag |
| Brand name in the title | Compatibility is the point | Lower return risk, less duplicate hardware |
| Numeric size in the name, like 2-in. | Size match matters | Compare against the old part before ordering |
Keep the removed part in a labeled bag until the tank runs through a full refill cycle. That habit saves the model number for the next order and keeps mixed screws out of the junk drawer.
What We Did Not Pick
A few universal kits missed the cut because they ask the buyer to do more compatibility work than a slow-fill repair deserves. American Standard, Plumb Pak, Keeney, and Lasco all sell replacement parts in this space, but the broad kits from those brands do not beat the cleaner fit logic of the five picks above.
Generic packs also leave more spare bits behind. That is fine for a drawer full of plumbing odds and ends, not fine for a buyer who wants one repair with less cleanup and less second-guessing.
Final Buying Checklist
- Pick Fluidmaster 400H when the tank needs a broader refresh, not just one valve.
- Pick Korky 528MP when the flapper still seals and the refill valve is the weak spot.
- Pick TOTO TSU01R only for TOTO tanks.
- Pick KOHLER K-46320 only for Kohler tanks.
- Pick Danco 10705 for a straightforward generic swap.
- Stop and solve the supply-line or shutoff problem first if the slowdown starts upstream.
- Take a photo of the old assembly before removal, then keep the old part and the package together until the repair is done.
Final Recommendations
For most homes, Fluidmaster 400H is the best toilet repair kit for a slow fill because it covers the broadest common tank-side repair without turning the job into a parts hunt. The cost trade-off is extra hardware, and that buys coverage, not clutter.
The budget lane belongs to Korky 528MP when the flapper still seals and the fill valve is the only weak point. Danco 10705 wins when the job needs the simplest generic swap. TOTO TSU01R and KOHLER K-46320 belong in their branded tanks, where the parts match beats a universal guess.
If the main goal is one solid repair with the least risk of leaving half the problem behind, start with Fluidmaster. If the toilet is brand-specific, respect the brand. That is where the cleanest fix lives.
FAQ
Is a toilet repair kit enough for a slow fill?
Yes, when the slow refill starts in the tank hardware. A fill valve or flapper kit handles that repair path directly. It does not fix a kinked supply line, a partly closed shutoff valve, or low incoming water pressure.
Do TOTO and Kohler toilets need brand-specific kits?
Yes. TOTO TSU01R and KOHLER K-46320 make sense because the tank design calls for a matched path. Generic kits work on many toilets, but brand-specific parts cut down on fit problems and return risk.
Is the cheapest kit the right pick for most slow-fill toilets?
No. The cheapest kit wins only when the flapper still seals and the fill valve is the part that needs replacement. If the tank hardware shows broader wear, the more complete Fluidmaster route is the better buy.
Does a broader repair kit create more cleanup?
Yes. More parts mean more pieces to sort, bag, and store during the repair. The trade-off is better coverage when the tank needs more than one worn part replaced.
What slow-fill problem does no kit fix?
A supply-side problem sits outside the kit. A closed or failing shutoff valve, a kinked line, or a plumbing issue upstream needs a different repair than a toilet tank kit.
What should I check before ordering?
Check the toilet brand, the repair scope, and the shape or size marking on the old part. Those three checks stop the wrong kit from turning into a second store run.
See Also
If you want to pressure-test this shortlist, read Quiet Home Repairs: Best Noise-Reducing Power Tool for First-Timers, Best Silicone Sealant for Kitchen Sink Edges (2026): What to Buy, and Best Stud Finders for Home Use in 2026 next.
For more context beyond the main ranking, Quartz vs. Quartzite Countertops: Which Should You Choose? and Klein Tools Et310 Review: a No Nonsense Circuit Breaker Finder add useful comparison detail.