# RO and UF Filtration: What Is the Difference?

How the two most common membrane systems work, where each one shines and what to weigh up.

- Page: https://demo.coway.one/en/articles/ro-vs-uf-filtration
- 24 Oct 2026

RO and UF are the membrane systems you will meet most often in home water purifiers. They work differently, so each suits a different kind of water.

## What is RO?

RO stands for reverse osmosis. Pressure pushes water through a membrane with pores of around 0.0001 microns, which removes much of what is dissolved in the water, minerals included. Some water goes to waste during filtering, and the system usually relies on a pump.

## What is UF?

UF stands for ultrafiltration. Its membrane has pores of around 0.01 microns, which catches fine sediment and many microorganisms while dissolved minerals pass through. It does not reduce dissolved substances.

## At a glance

| Topic | RO | UF |
| --- | --- | --- |
| Approximate pore size | 0.0001 microns | 0.01 microns |
| Reduces dissolved substances | Yes | No |
| Minerals in the water | Greatly reduced | Retained |
| Waste water while filtering | Yes | Generally less |

## Which should you choose?

RO often suits water that is high in dissolved solids or tastes brackish. UF is worth considering for good mains water when you want to keep the minerals. Decide alongside a water quality test.