Insufficient Functional Disclosure Sinks Brita’s Water Filtration Patent at the Federal Circuit

By: Nayyer Siddiqi

In Brita LP v. International Trade Commission (Case 2024-1098, decided October 15, 2025), the Federal Circuit affirmed the International Trade Commission’s determination that certain claims (1–6 and 23) of U.S. Patent No. 8,167,141 are invalid for lack of written description, lack of enablement, and indefiniteness. This ruling emphasizes the strict boundaries around functional claiming.

Background

Back in 2012, Brita LP (which is a subsidiary of Clorox) received U.S. Patent No. 8,167,141 for a gravity-fed water filtration system. The key independent claim describes a filter with “filter media including at least activated carbon and a lead scavenger” that has a Filter Rate and Performance (FRAP) factor of around 350 or below. Moving forward to December 2021, Brita took several companies to the International Trade Commission, claiming patent infringement.

Findings of the Court

The Federal Circuit undertook a de novo review of the Commission’s legal conclusions, while examining the factual findings under a substantial evidence standard.

With respect to written description issues, the Court held that the patentee failed to demonstrate possession of the full claimed scope. While the claims covered any filter media that could meet the functional FRAP requirement, the patent specification only described carbon block filters as being able to achieve those performance numbers. The examples and diagram only showed carbon-block setups. Additionally, the specification explicitly acknowledged that none of the mixed media filters they tested could satisfy the FRAP range they were claiming, and the patent characterized their carbon block formulations as uniquely capable of meeting these standards. Brita argued that since those skilled in the art already knew about other filter media types, their carbon-block disclosure was sufficient. The Court disagreed, emphasizing that for broad functional claims to satisfy the written description requirement, “the patentee must demonstrate he has invented species sufficient to support a claim to the functionally-defined genus,” citing Ariad, 598 F.3d at 1349. According to the Court, the specification did not explain what carbon-block filters had in common with other filter types that would let them achieve the FRAP factor and did not show that achieving the FRAP factor was something that could be separated from the specific properties of carbon blocks.

With respect to enablement, the Court found that the specification failed to enable one skilled in the art to make and use the entire claimed class without undue experimentation, applying Amgen Inc. v. Sanofi, 143 S. Ct. 1243 (2023). According to the Court, there was no guidance on how to achieve the FRAP value using anything other than carbon blocks. The Court held that the specification itself, not the knowledge of skilled artisans, should supply the novel aspects of an invention to constitute adequate enablement.

Implications

This decision underscores the limits of functional claiming. Patent attorneys should ensure that broad functional limitations are backed up by sufficient disclosure covering as much of the claims scope as possible. The patentee may not overcome unpredictability in achieving functional results by pointing to the general knowledge of those skilled in the art. The specification has to provide clear direction for practicing each claimed version of the invention, especially when claims seek extensive functional coverage.

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Background

Findings of the Court

Implications

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