Hydro Flask · Insulated Drink Tumblers
Hydro Flask Tumbler
Low risk. Stainless exterior, interior coating unknown.
Hydro Flask tumblers use stainless steel exterior with an unspecified interior coating. The brand hasn't disclosed PFAS status; interior lining remains unclear.
We flunk more products than we pass. This one earned its grade. How we grade
Material
stainless steel with unspecified interior coating/lining
Lab data
No public lab test
What Hydro Flask Tumbler is made of, ingredients and materials
Hydro Flask tumblers are double-walled stainless steel with an unspecified interior polymer or epoxy-based coating designed to enhance insulation and durability. The stainless steel exterior (typically 18/8 or similar food-grade alloy) is highly corrosion-resistant and does not leach under normal beverage conditions. The interior coating composition is not publicly disclosed by the brand, which limits independent assessment of potential lining degradation or migration of coating components into liquids.
What’s concerning
Category baseline
The starting point for this type of product, before anything specific to this product is counted.
No PFAS disclosure
No public statement from the brand about PFAS in this product.
Interior coating composition and migration
The interior coating material is not disclosed; if it contains epoxy or other polymeric liners, long-term exposure to hot or acidic beverages could theoretically cause minor migration. No documented cases reported for Hydro Flask, but lack of transparency prevents full assessment.
Coating degradation and flaking
Double-walled stainless tumblers can experience interior coating wear with repeated thermal cycling or dishwasher use. Flaking would be visible and signal product replacement; acute toxicity risk is low but indicates loss of insulation integrity.
Bacterial or mold growth in lid/seam
Like all insulated tumblers with tight seals, the lid threads and inner seam can trap moisture and become breeding grounds for bacteria or mold if not dried completely. This is a maintenance issue, not a material hazard, and applies to all similar products.
What’s reassuring
Base material not linked to PFAS
The main material recorded for this product is not one associated with PFAS.
Stainless steel alloy leaching (nickel, chromium)
Food-grade stainless steel (18/8) does not leach detectable nickel or chromium under normal beverage storage conditions. This risk applies mainly to lower-quality alloys or damage to the steel surface, neither of which is established for this brand.
Seal or gasket off-gassing
Hydro Flask tumblers typically use silicone or rubber gaskets; no VOC off-gassing or odor complaints are documented. Seals should be inspected for cracks but do not contact liquid directly in this design.
The full breakdown
The brand's record and disclosure
Hydro Flask has not issued public statements on PFAS use, PFOA avoidance, or material transparency regarding interior coatings. The brand is owned by Helen of Troy Limited and markets products as durable and insulated but does not provide third-party certifications (e.g., NSF, Cradle to Cradle) for food-contact safety. No major recalls specific to leaching or coating failure have been documented in public records for this product line.
How it compares in its category
Stainless steel insulated tumblers have lower concern because the exterior material is inert and the interior does not contact hot liquids at the container walls. Compared to plastic tumblers (which carry BPA/phthalate and microplastic heating risks) or ceramic-lined alternatives (which risk glaze lead contamination), stainless steel with a sealed interior coating is lower-risk. However, competitors like Klean Kanteen and S'well publish more detailed material disclosures, and some brands certify PFOA/PFAS-free coatings explicitly.
If you buy it
Avoid prolonged storage of acidic beverages (citrus, vinegar-based drinks) which may degrade the interior coating over time. Hand wash rather than dishwasher to reduce coating wear. Do not use boiling water repeatedly in the tumbler as thermal stress may compromise the seal or coating adhesion. Replace if you notice flaking, discoloration, or metallic taste in stored liquids, which would signal coating failure.
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 Drink Tumblers
Klean Kanteen
20oz TKWide with Café Cap, Tofu
- Stainless steel bottle, stainless steel cap
- The brand calls it PFAS-free, which we have not verified
- Powder-coat cap degradation over time
3 hazards checked on this product. See all of them.
Klean Kanteen
16oz Rise Tumbler
- Stainless steel body, powder-coat finish
- The brand calls it PFAS-free, which we have not verified
- Powder-coat finish degradation
3 hazards checked on this product. See all of them.
Klean Kanteen
Insulated TKWide Cap
- Stainless steel bottle, plastic cap and silicone gasket
- The brand calls it PFAS-free, which we have not verified
- Silicone gasket degradation and leaching
3 hazards checked on this product. See all of them.
More insulated drink tumblers 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.