- Water Quality: Most likely, the water you’re using might be causing the metallic taste. Certain waters, which may have a low ppm TDS (under 80), the water may be leaching the metallic taste from the espresso machine’s internal metal components. We have found that changing to a water that has more minerals up to 120ppm TDS, the situation improves. Keep in mind that measuring the TDS of a water today may change over time as well.
- Materials: Sometimes, the materials or oils used in the manufacturing of the espresso machine can affect the taste. We suggest running the aforementioned water to flush out the espresso machine.
- Descaling/Backflushing: Too much descaling and/or too much backflushing can expose the metals internally and water too low in TDS can create water that tastes metallic. Flush out the machine using the aforementioned water.
- Mineral Build-up: In some cases, hard water can cause metallic deposits from the water itself inside the espresso machine that might affect taste. Regular descaling can help keep things clean.
Some customers have stated that they did not have an issue with an older machine, including ones of the same make and model. Please keep in mind that manufacturers will over time change the internal components of the same model. For example, we had a customer with an old Rancilio Silvia espresso machine with a synthetic resin-made by polymerizing tetrafluoroethylene on the inside of the boiler with no issue of metallic taste. However, when the customer replaced it with a new Rancilio Silvia M espresso machine without the inside coating, the brand-new machine was emitting a metallic taste. The reason is that the water used did not react with the coating on the first unit, but it did react with the unit on the replacement espresso machine. Once the water was changed, the problem went away.
Hence, once can use the same water for years, but that same water can cause an issue on the same or different make and model espresso machine. And, sometimes the water source can change over the course of time or if the water comes from a different source or spring.
More can be read about water sources and choices. 1st-line Equipment, LLC also offers some videos about water choices, treatment, etc.
If you’ve tried these steps and the problem persists, it might be worth contacting the manufacturer, dealer or a professional technician to check for any underlying issues.