Fluidmaster K-400H-039 Fill Valve and Flapper Repair Kit
- 2 inch adjustable flapper included
- PerforMAX fill valve in the same kit
- 80 psi maximum pressure
- 7 year limited warranty
- CSA and ULC listed
Last refreshed Sep 8, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A two-part repair kit for a toilet that runs on or fills slowly, replacing the fill valve and flapper together. Check that your flush valve opening matches the flapper size before ordering.
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ASIN: B09NYLJ1FZModel: K-400H-039Category: Toilet Flappers
Overview
Fluidmaster combines its PerforMAX fill valve with an adjustable flapper in one kit aimed at running or slow-filling toilets. The valve handles refilling the tank and the flapper seals the flush opening between flushes.
Replacing both wear parts in one go saves a second trip when a tank is leaking and filling poorly at the same time. The limit is fit, because the kit suits a flush opening of one particular size only.
Who it's for
A bathroom with a tank that hisses, refills slowly or never quite shuts off is the target here. Owners of toilets with a larger flush opening should measure first, because the flapper is sized for one opening only.
Pros and cons
- Fill valve and flapper in one kit
- Flapper is adjustable
- Seven year limited warranty
- CSA and ULC listed
- Flapper only suits one opening size
- Plastic housing throughout
- Inlet and outlet details are unusual for a fill valve
- No dimensions for the tank clearance
Performance notes
A fill valve stops water when the float reaches the set height, and a leaking flapper lets water trickle into the bowl so the valve refills again and again. Replacing both removes the two most common causes of a toilet that runs, though the flapper only seals if the flush seat is clean and undamaged.
Where it stands among toilet flappers
- #10 most-searched brand and model of the 11 toilet flappers lines we track (by search demand, not sales).
From the specs of the 31 toilet flappers we list; not a test result.
Specifications
| Brand | Fluidmaster |
|---|---|
| Model | K-400H-039 |
| Dimensions & fit | |
| Flush valve size | 2 inches |
| Size | Universal, for 2 In. |
| Item Dimensions | 3.54 x 6.3 x 2.38 inches |
| Construction & materials | |
| Material Type | Plastic |
| Included components | |
| Included Components | PerforMAX Toilet Fill Valve, 2-Inch Flapper |
| Number Of Packs | 1 |
| Warranty & support | |
| Manufacturer Warranty Description | 7 Year Limited |
| Other details | |
| Valve Type | PerforMAX Toilet Fill Valve |
| Outlet Connection Type | FNPT |
| Inlet Connection Type | Female Iron Pipe |
| Thread Type | NPT |
| Maximum Pressure | 80 psi |
| Specification Met | CSA, ULC |
| Item Type Name | Toilet Repair Kit |
| Set Name | SET |
Frequently asked questions
How do I keep the Fluidmaster K-400H-039 flapper working over time?
The flapper is adjustable, so set it to seal against the flush seat and recheck if the tank starts to run again. The listing gives no cleaning or replacement interval.
What is in the Fluidmaster K-400H-039 kit?
The listing includes a PerforMAX toilet fill valve and a 2-inch flapper.
Will the Fluidmaster K-400H-039 flapper fit a larger flush valve opening?
No. The listing says universal for 2 inch, so a different opening size needs a different flapper.