Reverse osmosis systems for the home

12 models in this section

Reverse osmosis: the deepest water filtration

Osmosis differs from every other filter in that it does not trap impurities but separates the water. All its advantages and all its inconveniences follow from that.

How it works

Water is pushed under pressure through a membrane with pores so fine that practically only water itself passes. Everything else, hardness salts included, stays on the other side and is flushed to the drain. That is why osmosis has something flow filters do not: part of the water goes to waste, and that is the operating principle rather than a fault.

What a system consists of

Part	What it is for
Pre-filters	Several stages ahead of the membrane. They take out chlorine and particles, without which the membrane fails quickly.
Membrane	The heart of the system. It outlasts the cartridges and is changed less often; each model has its own.
Storage tank	Osmosis produces water slowly, so it collects in a tank. The tank is what takes up most of the space under the sink.
Post-filter	The final stage before the tap. On some systems this is a module with added magnesium.

Why a magnesium module

The membrane does not distinguish harmful from useful: along with hardness salts it removes minerals too. That is why the range includes modules with added magnesium, such as Pro Mg, which return it to the already filtered water. If that matters to you, check the stage list on the page of the specific system, because not every model has such a module fitted as standard.

Osmosis needs mains pressure. On upper floors and in areas with weak pressure the system works more slowly and the tank takes longer to fill. If your pressure is weak, it is worth saying so before buying: models with a pump exist, and the choice between those and an ordinary system turns on exactly this.