RO vs UV vs UF
The three technologies in almost every water filter, what each one removes, and which combination suits your water.
RO, UV and UF are the three technologies you’ll see in almost every water filter. They are not interchangeable: each one solves a different problem, and many systems combine them.
RO (reverse osmosis)
Water is pushed through a very fine membrane that holds back most dissolved salts, metals and other contaminants. It is the only one of the three that lowers TDS. It needs enough water pressure (often a booster pump) and sends some water to the drain.
UV (ultraviolet)
Water passes a UV lamp that inactivates bacteria and viruses. It adds nothing and removes nothing, so it doesn’t change taste or TDS, and it only works well on clear water. It needs electricity.
UF (ultrafiltration)
A membrane with larger pores than RO removes particles, cloudiness and many bacteria without removing dissolved salts. It usually works without electricity.
Side by side
A quick comparison of what each technology does.
| Feature | RO | UV | UF | Sediment + carbon |
|---|---|---|---|---|
| Removes dissolved salts (lowers TDS) | Yes | No | No | No |
| Protects against bacteria and viruses | Yes, the membrane is a barrier | Yes, inactivates germs | Partly, removes bacteria | No |
| Reduces chlorine, smells and bad taste | Yes, with carbon pre-filters | No | No | Yes |
| Removes sand, rust and cloudiness | Yes, with a sediment pre-filter | No, water must already be clear | Yes | Yes |
| Needs electricity | Usually, for the pump | Yes | No | No |
| Sends some water to the drain | Yes | No | No | No |
| Best suited to | Water with high TDS, salty or bitter taste | Clear water with low TDS where germs are the worry | Low-TDS water that is cloudy or may carry bacteria | Taste and smell problems in otherwise good water |
Most home systems combine stages, for example sediment and carbon pre-filters, an RO membrane and a UV or mineral stage. A water test shows which combination you need.
Which one do I need?
Answer a few questions for a suggestion based on your water.
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