RO: membrane separation
Pressure drives water through a semi-permeable membrane. It is relatively fast and energy-efficient compared with boiling every litre, but creates a reject stream and depends on membrane/pre-filter condition.
Distillation: evaporation and condensation
A distiller boils water and condenses the vapour. Many dissolved salts and non-volatile contaminants remain behind. CDC notes that some volatile organic compounds can pass through distillation unless the system is designed to address them.
| RO | Distillation | |
|---|---|---|
| Main mechanism | Pressure + membrane | Boil + condense |
| Mineral reduction | High | High |
| Water reject | Yes | Concentrated residue remains in boiler |
| Energy | Pumps; countertop units may heat separately | High heat input for evaporation |
| Speed | Generally faster | Generally slow |
Which tastes better?
That is personal. Both can taste “flat” to people accustomed to mineralised water. Remineralisation changes RO taste deliberately; distilled water can also be used for technical applications where minerals are undesirable.
Some devices explicitly request distilled or demineralised water; others are designed around ordinary tap water. Do not treat “RO” and “distilled” as interchangeable labels when a medical device, humidifier, iron or laboratory-style appliance specifies a particular water type.
For appliances, follow the appliance specification
An RO owner replaces prefilters and eventually a membrane, and may need to sanitise storage and water paths. A distiller accumulates the non-volatile material left behind after boiling and needs regular cleaning/descaling of the boiling chamber. Neither technology is maintenance-free.
Maintenance is different too
Sources and further reading
For factual claims that matter to health, regulation or product performance, we prefer primary and official sources. Useful references for this guide include:
- CDC — About home water treatment systems
- Drinking Water Inspectorate — Physical removal of contaminants
Related guides
Last reviewed: 6 October 2026. This guide is written for a UK audience. Always follow current supplier, regulator, manufacturer and healthcare advice where it applies.