Is it safe to store bottled water in the garage over winter?
No. Cold and thaw cycles accelerate plastic aging and microplastic release.
What's actually in it
PET water bottles stored in an unheated garage go through repeated freeze-thaw cycles across winter months. Water expands when it freezes, stretching the plastic. The bottles then thaw and the process reverses. Each cycle creates micro-cracks in the plastic surface that accelerate microplastic shedding and chemical migration.
Many people buy cases of water in bulk and store them in the garage or basement. Rotation can be slow.
What the research says
A 2026 study in Environ Sci Technol examined suboptimal thermal storage of bottle-sourced PET microplastics and their effect on hepatic steatosis. Aged PET microplastics, produced by thermal cycling, caused greater liver injury and metabolic stress than fresh particles. Storage temperature fluctuations were a major driver of aging.
For emergency water supplies, store indoors at stable room temperature and rotate every 6 months. For daily drinking, a home carbon or reverse osmosis filter with a stainless or glass bottle avoids the whole storage question. If bulk bottled water is the only option, buy smaller quantities more frequently rather than stockpiling a winter's worth.
The research at a glance
| Study | Journal | Year |
|---|---|---|
| Suboptimal Thermal Storage Facilitates Aging of Bottle-Sourced Polyethylene Terephthalate Microplastics Fueling Hepatic Steatosis. | Environ Sci Technol | 2026 |
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