Wash your thermos daily with warm, soapy water.
Use a bottle brush to clean the interior and lid.
Disinfect weekly with a vinegar or baking soda solution.
👉 Note: Even plain water can become contaminated if the container isn’t hygienic.
3. Alkaline Water or Ionized Water
🚫 Why it’s problematic:
Alkaline water (typically with a pH of 8–10) is marketed for its health benefits, but it can be corrosive to certain metals — especially over time.
Many thermoses are made with stainless steel interiors, which are generally safe — but prolonged exposure to high-pH water can:
Degrade the metal lining, especially if the thermos has micro-scratches.
Leach metals like nickel or chromium into the water.
Damage the vacuum seal due to chemical reactions.
➡️ Risk: Long-term use may compromise both the thermos and your health.
✅ Safer alternatives:
Store alkaline water in glass or BPA-free plastic containers.
Drink it immediately rather than storing it for hours.
Check your thermos manufacturer’s guidelines — some explicitly warn against alkaline or ionized liquids.
Bonus: What Else Should You Avoid in a Thermos?
While not “water,” these liquids also pose risks:
Milk or plant-based milks – Can spoil quickly and harbor bacteria.
Juices with pulp – Hard to clean and ferment over time.
Acidic drinks (like lemon water) – Can corrode metal over time, especially if stored for hours.
Best Water to Store in a Thermos
✅ Plain filtered or bottled water
✅ Herbal teas (cooled slightly if using a glass-lined flask)
✅ Electrolyte water (if consumed within a few hours)
