Hydro Flask · Insulated Travel Mugs
Hydro Flask 12 oz Outdoor Tumbler
Stainless steel tumbler with no known PFAS hazards.
Double-wall stainless steel with foam insulation, inherently lower PFAS risk by design. Brand makes no PFAS disclosures, but core material and construction pose minimal typical concerns.
The better-graded swap
Thermos
Thermos Stainless Steel Mug
80/100 safety
Same rubric that flunked this product. The swap earned Excellent.
Still want this one anyway? Check the price on Amazon. We’d swap it.
Material
Stainless steel wall construction with foam insulation
Lab data
No public lab test
What Hydro Flask 12 oz Outdoor Tumbler is made of, ingredients and materials
The Hydro Flask 12 oz tumbler uses food-grade 18/8 stainless steel (outer and inner walls) with closed-cell foam insulation sandwiched between them. Stainless steel does not leach metals like aluminum or cadmium under normal use because it is a stable alloy that resists corrosion. The foam insulation is inert when sealed inside the walls and poses no direct contact risk to beverages. This material combination avoids the primary failure modes that affect other tumbler types (ceramic chip risk, plastic coating degradation, aluminum leaching).
What’s concerning
No PFAS disclosure
No public statement from the brand about PFAS in this product.
Category baseline
The starting point for this type of product, before anything specific to this product is counted.
Coating degradation and foam exposure
If the seal between stainless steel walls fails due to impact or manufacturing defect, foam insulation could come into direct contact with beverages. While the foam itself is inert, this represents a product failure mode rather than a chemical hazard. No recalled failures are on record for this specific model.
What’s reassuring
Base material not linked to PFAS
The main material recorded for this product is not one associated with PFAS.
Lid gasket and closure material safety
Hydro Flask does not publicly disclose the material composition of lid gaskets, seals, or closure mechanisms. Silicone is commonly used in similar products, but specific material data for this tumbler is unavailable in public sources.
Stainless steel leaching under extreme conditions
Stainless steel is highly resistant to leaching, but prolonged exposure to very acidic beverages or salt solutions at warm temperatures could theoretically cause minor nickel or chromium migration. This is not a documented hazard for this product under normal use conditions.
Lead
Hydro Flask tumbler exteriors feature printed logos and designs, but no public safety data on the inks used is available. No recalls or safety alerts related to exterior decoration have been recorded.
Source, ATSDR ↗Aluminum leaching
This product is stainless steel, not aluminum, so aluminum leaching is not applicable. Included here to clarify the material advantage over competing aluminum tumbler designs.
The full breakdown
The brand's record and disclosure
Hydro Flask does not publicly disclose detailed material sourcing, manufacturing processes, or third-party safety testing results on their website. The brand has not faced major product recalls or safety controversies in publicly available records. They market their products for beverages and food use, but transparency on chemical testing or PFAS avoidance strategies is minimal. No independent certifications (NSF, FDA pre-market approval) are claimed in marketing materials reviewed.
How it compares in its category
Stainless steel tumblers like this present lower concern than ceramic-coated alternatives (which can chip and expose lead-bearing glazes) or plastic tumblers with interior coatings prone to degradation. Compared to aluminum tumblers (which can leach if uncoated or damaged), stainless steel eliminates that risk entirely. The closed insulation design is superior to open-wall designs because it prevents foam contact with liquids. This product sits in a lower concern tier of the reusable tumbler market.
If you buy it
Hand wash only; dishwasher use can degrade seals between walls over time, risking foam exposure. Do not use for extended storage of acidic liquids (citrus, vinegar) beyond a few hours, as even stainless steel can develop micro-pitting under prolonged acid stress. Replace if the outer or inner wall develops visible dents or damage that might compromise the seal. The lid gaskets are the wear point; inspect them annually and replace if cracked or degraded to maintain insulation and prevent leaks.
What we don’t know
- Basis
- Model estimate, 72% confidence, not a lab result
- Lab test
- None on record for this exact product
- Brand statement
- Hydro Flask has made a specific claim
Formulations change between production runs, so check the current label. How we grade.
Better-graded alternatives in Insulated Travel Mugs
Owala
FreeSip Sway Stainless Steel
- Stainless steel body, no interior coating disclosed
- Silicone and plastic lid/valve leachables
3 hazards checked on this product. See all of them.
Owala
Stainless Steel Straw Tumbler Route 66
- Stainless steel tumbler, bare uncoated
- Coating degradation and microplastic shedding from exterior print
3 hazards checked on this product. See all of them.
Thermos
18 oz. Icon Vacuum Insulated Stainless Steel Mug
- stainless steel exterior, vacuum insulation, stainless steel interior
- We found no PFAS statement from the brand
- Nickel leaching from stainless steel
3 hazards checked on this product. See all of them.
More insulated travel mugs 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.