Fluidmaster K-400H-039 Fill Valve and Flapper Repair Kit
- Outlet Connection Size: 2 inches
- Inlet Connection Size: 2 inches
- Thread Size: 2 inches
- Valve Type: PerforMAX Toilet Fill Valve
Last refreshed Sep 8, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A two-in-one fix for a running or slow-filling 2-inch-valve toilet, replacing the fill valve and flapper together instead of guessing which part failed.
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ASIN: B09NYLJ1FZModel: K-400H-039Category: Toilet Flappers
Overview
Fluidmaster's K-400H-039 kit pairs a PerforMAX fill valve with an adjustable 2-inch flapper to address a toilet that runs continuously or fills slowly, replacing both wear-prone parts in one kit for tanks with a 2-inch flush valve.
Rather than guessing whether the fill valve or the flapper caused a running toilet, this kit replaces both at once. Fluidmaster is the name most tank hardware is already built to match, which helps with fit in older tanks.
- PerforMAX fill valve included
- Adjustable 2-inch flapper
- Fixes running or slow-filling toilets
- Replaces two wear parts in one kit
Who it's for
Homeowners whose toilet keeps running or fills slowly and want to replace both the fill valve and the flapper together, on a tank with a 2-inch flush valve opening. It is not sized for 3-inch valve toilets like many Gerber models.
Pros and cons
- Replaces two common failure parts in one kit
- Flapper is adjustable to tune flush volume
- Only fits tanks with a 2-inch flush valve
- Two parts to install instead of one if only the flapper failed
Performance notes
The PerforMAX fill valve controls how the tank refills after a flush, while the adjustable 2-inch flapper controls how long the valve stays open during a flush, so together they govern both refill and flush volume. Replacing both parts at once removes the guesswork of diagnosing which one wore out.
Specifications
| Brand | Fluidmaster |
|---|---|
| Model | K-400H-039 |
| Dimensions & fit | |
| Outlet Connection Size | 2 inches |
| Inlet Connection Size | 2 inches |
| Thread Size | 2 inches |
| Item Weight | 0.84 pounds |
| Size | Universal, For 2 In. |
| Item Dimensions | 3.5 × 6.3 × 2.4 inches |
| Construction & materials | |
| Material Type | Plastic |
| Exterior Finish | Plastic |
| Included components | |
| Number Of Pieces | 1 |
| Number Of Packs | 1 |
| Unit Count | 1 |
| Included Components | PerforMAX Toilet Fill Valve, 2-Inch Flapper |
| 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 |
| Number Of Ports | 2 |
| Connector Type | Female Iron Pipe, FNPT |
| Thread Type | NPT |
| Number Of Items | 1 |
| Item Type Name | Toilet Repair Kit |
| Item Highlight | Includes high-performance fill valve and adjustable 2 in. flapper, Helps fix running or slow-filling toilets |
| Set Name | SET |
| Maximum Pressure | 80 psi |
| Specification Met | CSA, ULC |
Frequently asked questions
What does the K-400H-039 kit include?
A PerforMAX fill valve and an adjustable 2-inch flapper.
What problem is this kit meant to fix?
A toilet that runs continuously or fills slowly because of a worn fill valve or flapper.
Does this fit a 3-inch flush valve?
No, the included flapper is sized for a 2-inch flush valve opening.