A metallic taste in water carries straight through into coffee, and it usually comes from the pipes rather than the supply.
Household plumbing
Copper pipes, especially new ones or after standing overnight, leach small amounts of copper. It tastes distinctly metallic.
Iron from old steel pipes gives a blood-like or rusty note, sometimes with visible discoloration.
Lead, in very old properties. Not something to taste-test for — if you suspect lead plumbing, have the water tested properly.
The standing-water effect
Water that has sat in pipes overnight picks up far more metal than water that has just flowed.
Run the cold faucet for 30 seconds before filling for coffee. This alone solves a lot of complaints.
The machine
A new aluminum moka pot tastes metallic until seasoned — brew and discard two or three times.
A scaled or corroding boiler, particularly one run on RO or very soft water, which is aggressive to brass and copper.
Old, worn tubing in super-automatic machines.
Low-mineral water
Very soft or RO water is corrosive, and it will dissolve metal from whatever it passes through. A metallic taste appearing after switching to RO water is this.
Remineralize it.
The fixes
Run the faucet before filling. Carbon filtration, which reduces dissolved metals somewhat. Have the supply tested if it persists on freshly run water.
When to take it seriously
Persistent metallic taste from a fresh-run cold faucet in an old building warrants a proper water test.
Last reviewed 30 October 2026