Why Does Water from a Plastic Kettle Taste Different to Water from a Metal One? The Science Behind the Sip

If you’ve ever brewed a cuppa and found it tasted a little… off, you’re not alone. Many people claim that water boiled in a plastic kettle doesn’t taste as nice as water boiled in a metal kettle, and this isn’t just snobbery or imagination. There’s real science behind the phenomenon.

Here’s a look into what might be going on in your kettle.

1. The Problem of Plastic Leaching

Plastic kettles are typically made from polypropylene or BPA-free plastics. While these materials are generally considered safe, heating them repeatedly—especially to boiling point—can cause trace chemicals to leach into the water.

Some of the common compounds include:

Phenols (like BPA substitutes)

Styrene monomers

Other manufacturing residues

Even in tiny amounts, these substances can alter the taste of the water. Your body might not notice it immediately, but your tongue certainly can. Many describe the taste as chemical, plasticky, or stale.

2. Off-Gassing and New Kettle Smell

Brand-new plastic kettles often emit a distinct "new plastic" smell when first used. This comes from volatile organic compounds (VOCs) used during manufacturing. These compounds are released (or "off-gassed") when the kettle is heated for the first few times.

This is why instructions often suggest boiling and discarding water several times before use. Even so, some kettles may retain that taint for weeks or longer.

3. The Inert Nature of Metal

Metal kettles, usually made of stainless steel, or sometimes copper, have a distinct advantage: they are chemically inert at high temperatures. This means:

No leaching of unwanted chemicals

No absorption of flavours over time

Easy to keep clean with no porous surfaces

Stainless steel doesn’t hold onto the taste of previous boils or absorb anything from the water, which results in cleaner-tasting water, ideal for tea and coffee purists.

4. Mineral and Limescale Interactions

Plastic kettles often have heating elements hidden beneath the base. In contrast, metal kettles (especially stovetop models) use exposed metal heating. This may influence how limescale and minerals accumulate, particularly in hard water areas.

Some studies suggest that mineral deposits may form differently on plastic versus metal, subtly influencing mouthfeel and flavour.

5. Sensory Psychology and Perception

There’s also a psychological angle: we often associate plastic with cheapness or artificiality, and metal with tradition and purity. These expectations can colour our sensory experience, particularly with taste and smell.

In blind tests, people may still prefer metal-boiled water, but the difference is often more pronounced when the participants know the source.

Conclusion: Is It All in the Kettle?

Not entirely. While personal preference plays a role, science supports the idea that plastic kettles can affect the taste of boiled water through leaching compounds, off-gassing, and minor chemical interactions. Metal kettles, especially stainless steel ones, tend to offer a cleaner, more neutral brew.

So, if you’re serious about your tea or coffee, or just don’t like that odd aftertaste, switching to a metal kettle could be a small change that makes a big difference.

Top Tip: Want the best of both worlds? Try a glass kettle with stainless steel elements, you’ll get taste neutrality, no plastic taint, and a good view of your boil.