Clearly Filtered · Filtered Water Bottles
Grayl UltraPress Purifier Bottle
Lower-concern design; no known PFAS-prone materials, but brand offers no explicit disclosure.
The Grayl UltraPress uses borosilicate glass and coconut-shell carbon for filtration, materials with lower inherent PFAS risk compared to Teflon-family coating membranes. The polypropylene housing and silicone seals are not inherently PFAS-heavy, though the brand provides no PFAS transparency statement or third-party testing.
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Borosilicate glass filter cartridge; coconut-shell activated carbon; polypropylene housing
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
Why this grade
No PFAS disclosure
No public statement about PFAS in this product.
Uncoated safe material
Bare, uncoated material (cast iron, stainless, carbon steel, or glass) with no surface treatment to contain PFAS.
The full breakdown
What it's made of and why it matters
The Grayl UltraPress uses a borosilicate glass filter cartridge, which is chemically inert and does not leach into water even under stress. The activated carbon is derived from coconut shell, a benign source material that does not inherently contain heavy metals or synthetic binders of concern. The polypropylene (PP) housing (#5 plastic) is food-contact grade and stable at room temperature; PP does not contain BPA or phthalates by chemistry. The press mechanism and seals are designed to avoid contact between pressurized water and any problematic adhesives or coatings.
The brand's record and disclosure
Clearly Filtered markets the Grayl line as a purification tool but does not publish third-party certification reports (NSF, WQA) or detailed PFAS testing on the brand website. The company has not disclosed whether housing or seals were tested for leachables under normal use conditions. No major recalls or safety controversies have been recorded for this product model in public databases. The brand's silence on PFAS and material verification is a transparency gap, though material selection itself does not suggest PFAS risk.
How it compares in its category
Most filtered water bottles use activated carbon (safe) but often combine it with plastic housing that may contain antimicrobial coatings or undisclosed additives. The Grayl's borosilicate glass filter is a step above bottles that use plastic cartridges, reducing leaching risk. Competitors like LifeStraw and Larq offer similar or slightly better third-party certification transparency. The Grayl's press-and-sip design avoids the straw-clogging issues common in squeeze bottles, though it does not address source-water contamination beyond particulates and some chemicals.
If you buy it
Replace the filter cartridge every 40 gallons or per manufacturer guidance; used carbon loses adsorption capacity and can harbor bacterial biofilm if not swapped regularly. Store the bottle empty and dry between uses to prevent mold in the housing and seals. Do not expose the polypropylene housing to prolonged heat above 50C (122F) or direct sunlight, as this accelerates polymer degradation. Rinse all components under running water before first use; borosilicate glass is durable but can crack if dropped, so handle the filter cartridge with care.
Beyond PFAS: other things we checked
Established hazard classes for this product type, assessed from public information. These never change the PFAS grade; a Likely flag caps the Verdict at “Buy with care.”
Bacterial growth in filter cartridge
Activated carbon is a porous substrate that can retain moisture and support microbial growth if the cartridge is not replaced on schedule or if the bottle is stored with residual water. Proper drying and timely cartridge swaps mitigate this risk substantially.
Polypropylene housing degradation and microleaching
PP is generally stable for food contact, but prolonged UV exposure or heat above 60C can cause brittleness and potential microplastic shedding. The Grayl's housing is not treated with antimicrobial coatings or flame retardants on record, reducing this hazard.
Filter cartridge mechanical failure and seal leakage
Borosilicate glass can fracture if dropped or if internal pressure exceeds design limits during a press stroke. Silicone or rubber seals may degrade over time with repeated use and mineral-rich water, leading to bypass of unfiltered water.
Volatile organic compounds (VOCs) from housing or adhesive
No published reports of off-gassing from the Grayl's polypropylene or assembly adhesives. However, the brand does not disclose materials testing for VOC content, leaving this claim unverified by independent data.
Heavy metals in activated carbon source or processing residue
Coconut-shell activated carbon is generally free of heavy metal contamination if properly processed, but the manufacturer does not publish ash content or metal testing. Standard food-grade carbon should meet limits, but verification is absent from brand materials.
What we don’t know
This grade is a model-based estimate from public materials, coatings, and brand disclosure at 72% confidence. It is not a lab result.
No independent PFAS lab test is on record for this exact product. A lab test could move the score in either direction.
The brand has not made a specific, verifiable PFAS-free statement, so part of this score reflects that missing disclosure rather than a confirmed material.
Formulations and coatings change between production runs. Always check the current label before buying.
More filtered water bottles grades
How we score: every product runs through the same public 0–100 rubric based on materials, coatings, brand disclosure, lab findings, and recalls. See the full methodology → Spotted a mistake? Report an error.