3 Types of Water You Shouldn’t Store in a Thermos
A thermos is a fantastic tool for keeping your beverages hot or cold for extended periods. However, not all types of water are suitable for thermos storage.
Some can cause damage to the thermos or even pose health risks. Here are three types of water you should avoid storing in a thermos:
1. Boiling Water (Above 100°C)
It might seem logical to pour freshly boiled water into a thermos to keep it hot, but water that’s just come off a rolling boil (above 100°C) can be problematic. Here’s why:
- Pressure Buildup: Extremely hot water can cause steam to accumulate rapidly inside the thermos, increasing internal pressure. This might lead to leakage, difficulty opening the lid, or even damage to the seal over time.
- Scalding Risk: When you open a tightly sealed thermos with boiling water, there’s a risk of steam burns or hot water splashing out.
Tip: Let boiling water cool for a minute or two before transferring it to your thermos.
2. Carbonated Water
Sparkling or carbonated water should also be kept far from your thermos.
- Gas Expansion: The carbon dioxide gas in fizzy water expands in a sealed environment, especially when there’s a temperature change.
- Pressure Problems: This expansion creates pressure that can cause the lid to pop off unexpectedly or even damage the thermos’ structure.
- Loss of Fizz: The carbonation will likely dissipate quickly, defeating the purpose of storing fizzy water in the first place.
Tip: Store carbonated beverages in bottles designed to withstand internal pressure, like soda bottles or vacuum-sealed drink flasks made specifically for sparkling drinks.
3. Salt Water or Mineral-Rich Water
Water high in minerals (like hard water) or containing salt is another no-go for thermoses, especially stainless steel ones.
- Corrosion Risk: Salt and minerals can corrode the inner lining of a thermos, particularly if it’s made from metal.
- Metal Leaching: In some cases, prolonged contact may cause trace metals to leach into the water, which is not ideal for consumption.
- Residual Odors: These types of water can leave behind a metallic or musty smell that’s tough to clean out.
Tip: Stick to filtered or distilled water when storing it in a thermos long-term.
Final Thoughts
Thermoses are incredibly useful, but they’re not suitable for every kind of liquid. To prolong the life of your thermos and protect your health, avoid storing boiling hot water, carbonated water, and mineral- or salt-rich water. When in doubt, check the manufacturer’s guidelines—your thermos (and your tastebuds) will thank you.
