IP Law Daily, PATENT—Fed. Cir.: Invalidity of Brita’s gravity-flow water filter patent affirmed on appeal, (Oct 15, 2025)

By Ravindra Kumar Singh, B.L.

ITC correctly found that Brita's patent failed to satisfy the written description and enablement requirements under 35 U.S.C. §112.

In a precedential disposition, the U.S. Court of Appeals for the Federal Circuit upheld a U.S. International Trade Commission (ITC) ruling invalidating key claims of Brita LP’s gravity-fed water filter patent for lack of written description and lack of enablement under 35 U.S.C. §112. The court held that the patent’s specification disclosed only carbon-block filters, failing to demonstrate possession or enablement of other filter media types claimed under the same performance metric. The Federal Circuit affirmed the ITC’s decision in full on these grounds and declined to address indefiniteness (Brita LP v. International Trade Commission, No. 24-1098 (Fed. Cir. Oct. 15, 2025)).

Background. The appellant, Brita LP, is a leading manufacturer of water filtration products widely used in residential and consumer markets. The appellee, the U.S. International Trade Commission, is a federal agency empowered under Section 337 of the Tariff Act of 1930 to investigate unfair import practices, including patent infringement. The intervenors—Vestergaard Frandsen Inc. (doing business as LifeStraw), Kaz USA, Inc., and Helen of Troy Limited—are competitors engaged in designing, importing, and selling household filtration products. Kaz USA and Helen of Troy jointly market the PUR filter line, while Vestergaard produces LifeStraw, a portable water purification system. The intervenors were the respondents before the ITC, successfully defending against Brita's allegations of patent infringement.

The patent in question, U.S. Patent No. 8,167,141 (the ’141 patent), titled “Gravity Flow Filter,” was issued on May 1, 2012, and arose from a continuation-in-part application filed in September 2008. The ’141 patent covers gravity-fed water filtration systems designed to remove contaminants such as lead from drinking water. The key claim, claim 1, recites a “filter media including at least activated carbon and a lead scavenger” that achieves a Filter Rate and Performance (FRAP) factor of about 350 or less—a performance metric defined by the inventors through a mathematical formula incorporating flow rate, contaminant removal, and filter lifespan.

While the specification purports to apply the claimed FRAP performance to multiple types of filters—such as carbon blocks, mixed media, and membranes—all of its working examples, figures, and test results involve carbon-block filters alone. The patent itself acknowledges that no mixed media filters tested met the claimed FRAP range, and it describes carbon blocks as “unique in their ability to meet the required FRAP factor.”

Brita filed a complaint with the ITC on December 27, 2021, alleging that the intervenors imported and sold water filters infringing the ’141 patent. The ITC instituted an investigation (No. 337-TA-1294) in early 2022. Following a Markman hearing, the ITC’s Administrative Law Judge (ALJ) construed the key claim term “filter usage lifetime claimed by a manufacturer or seller of the filter” and found no indefiniteness, ultimately concluding that the asserted claims were valid and infringed—thus establishing a violation of Section 337.

On review, however, the full Commission reversed. In its September 22, 2023, decision, the ITC found the asserted claims invalid for lack of written description and lack of enablement, and held that the disputed term was indefinite. The Commission determined that the patent failed to show possession of or enable the full range of filter media purportedly covered by the claims, specifically non-carbon-block filters. Brita appealed to the Federal Circuit.

Written description. The Federal Circuit affirmed the ITC’s conclusion that Brita’s patent lacked adequate written description. The court applied the standard articulated in Ariad Pharmaceuticals, Inc. v. Eli Lilly & Co., 598 F.3d 1336 (Fed. Cir. 2010) (en banc), under which a patent’s specification must “reasonably convey to those skilled in the art that the inventor had possession of the claimed subject matter as of the filing date.”

The appellate court found substantial evidence supporting the ITC’s determination that the ’141 patent disclosed only carbon-block filters capable of meeting the claimed FRAP factor. All examples and test results involved carbon-block filters, and the patent explicitly stated that “no mixed media filters tested met the claimed FRAP factor range.” The inventors' own testimony confirmed that they “changed technology from a granular media to a carbon block” to achieve the claimed performance, evidencing a lack of possession of non-carbon-block embodiments.

Citing Regents of the University of California v. Eli Lilly & Co., 119 F.3d 1559 (Fed. Cir. 1997), the court reiterated that a “mere wish or plan” to obtain the claimed result cannot satisfy the written description requirement. It further emphasized that while claim 1 was broadly written to encompass any filter media achieving the FRAP factor, the patent failed to identify a representative number of species or common structural features uniting the genus of claimed filters.

The court rejected Brita’s argument that references to multiple filter types in the specification demonstrated possession of a broader genus. Relying on Enzo Biochem, Inc. v. Gen-Probe Inc., 323 F.3d 956 (Fed. Cir. 2002), the panel held that including general categories of filter media without specific, enabling examples does not satisfy §112. The ’141 patent's express limitation to carbon-block filters as the only working examples underscored that the inventors were in possession of only one species within the claimed genus.

Enablement. Turning to enablement, the court affirmed the ITC’s conclusion that Brita’s patent failed to enable the full scope of its claims without undue experimentation, consistent with Amgen Inc. v. Sanofi, 598 U.S. 594 (2023) and In re Wands, 858 F.2d 731 (Fed. Cir. 1988). The panel agreed that while the specification disclosed how to make carbon-block filters achieving the FRAP factor, it provided no teaching or roadmap for achieving comparable performance using mixed or granular media.

The ’141 patent itself described significant technical drawbacks in mixed-media filters, including long contact times, large spatial requirements, and hydrophobicity limiting water absorption. Yet, it offered no disclosure or guidance on overcoming these deficiencies. The court held that reproducing the claimed invention across all media types would require extensive experimentation, contrary to the enablement standard.

Expert testimony further supported the ITC’s findings. Brita’s own witnesses conceded that the variables in the FRAP equation—volume, filtration time, effluent concentration, and lifespan—were “interrelated in a nonlinear and unpredictable manner.” The inventors also admitted that achieving similar performance with non-carbon-block media would require “new technology.” Citing Genentech, Inc. v. Novo Nordisk A/S, 108 F.3d 1361 (Fed. Cir. 1997), the court emphasized that “it is the specification, not the knowledge of one skilled in the art, that must supply the novel aspects of an invention.”

The panel thus concluded that a skilled artisan could not make and use the claimed invention without undue experimentation, rendering the claims invalid for lack of enablement.

Indefiniteness. Having affirmed on written description and enablement, the court declined to reach the issue of indefiniteness, noting that under Solomon Technologies, Inc. v. ITC, 524 F.3d 1310 (Fed. Cir. 2008), it need not address every potential ground for sustaining the Commission’s decision.

The Case is No. 24-1098.

Judge: Prost, S.

Attorneys: Deanne Maynard (Morrison & Foerster LLP) for Brita LP. Panyin Hughes for the U.S. International Trade Commission. Adam Swain (Alston & Bird LLP) for KAZ USA, Inc., and Helen of Troy Limited. Jeffrey R. Gargano (K&L Gates LLP) for Vestergaard Frandsen Inc.

Companies: Brita LP; KAZ USA, Inc.; Helen of Troy Limited; Vestergaard Frandsen Inc.

Cases: Patent FedCirNews