
Kohler GP1078440
Score: 80/100
Kohler 1138648
Score: 75/100Rankings

The Kohler GP1078440 is a genuine 2-inch shark-fin style toilet flapper designed as a replacement part for select Kohler one-piece toilets. It features a corrosion-resistant rubber construction with a red finish and includes an adjustable chain for secure sealing and efficient flushing. This part is specifically engineered for bottom outlet flush valves to ensure a reliable fit.

The Kohler Genuine Part 1138648 Flapper Assembly is an OEM replacement component designed for Kohler toilets, specifically compatible with two-piece models manufactured prior to 2004 that utilize a 2-inch flapper design. It controls water flow from the tank to the bowl and is constructed from durable, chemical-resistant materials to ensure optimal performance and warranty protection. This part is essential for routine maintenance and DIY repairs on compatible units like the San Raphael K-3722.
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2 inchesbest | 2 inchesbest | |
1 countbest | 1 countbest |
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| Attribute | ![]() | ![]() |
|---|---|---|
Material & Durability(2) | ||
Material | Rubber | Chemical-resistant |
Seal Type | Shark-fin | null |
Design & Features(3) | ||
Chain Material | Not specified | null |
Chain Adjustability | true | false |
Flapper Type | Shark-fin | Flapper Assembly |
Compatibility & Fit(2) | ||
Flush Valve Compatibility | Bottom outlet | null |
Toilet Type Compatibility | One-piece | Two-piece |


Products in the top-left offer the best value (high score, low price).

No independent professional reviews, editorials, or expert analyses from recognized plumbing authorities or consumer reports are available in the source data. Retailers and Kohler's service pages describe the part positively as an essential component for reliable flushing and meticulously designed for performance, emphasizing its OEM quality.
There is a complete absence of consumer reviews, ratings, or testimonials in the available data. One listing explicitly notes zero customer reviews, making it impossible to identify common praise, complaints, or recurring themes from everyday users.
