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Reverse osmosis (RO)
A filtration method that forces water through a semi-permeable membrane, removing up to 99% of dissolved solids.
Category: Water Quality & Filtration
A water treatment method that pushes water through a semi-permeable membrane, removing nearly all dissolved solids — including hardness, minerals, chlorine, and contaminants. Output is very pure water with TDS under 10 ppm.
Why it matters — RO is the most thorough water treatment available. For very hard water areas where filtration alone isn't enough, RO followed by remineralisation produces ideal brewing water.
Good to know
- Pure RO water alone is too pure for coffee — it tastes flat and extracts poorly. Always remineralise after RO.
- RO systems waste water (typically 2–5 litres rejected per litre produced). Modern systems are more efficient but waste is part of the trade-off.
Related: Water Filtration