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How Reverse Osmosis Water Filters Work

How Reverse Osmosis Water Filters Work

Reverse Osmosis (RO) is a water purification method which works by a semi-permeable membrane separating water molecules from larger ions or pollutants.

It is a very efficient method for purifying water and relies solely on water pressure.

Our filter uses the latest technology RO membranes for efficient performance and high yield production.

The membrane filters down to 0.0001 microns.

(Just for comparison: a Human hair is 100 microns wide. Bacteria are between 0.2 to 1 microns. Viruses are between 0.02 to 0.4 microns).

The separation is usually 95-98% efficient with the recovery of purified water being around 15-20% of the volume processed in a single pass.

Our Reverse Osmosis systems offer advanced filtration and control which extends membrane life, reduces water loss and ensures reliable operation in a compact and easy to maintain module.

What are Reverse Osmosis Stages?

When researching which RO unit is the best for your needs you will probably come across terms like "5 stage" or "6 stage".

Stages refers to the number of filtering steps the water goes through before coming out of the tap into your glass or kettle.

Usually you have two or three pre-filters to clean the water before it goes through the "membrane" filter - which is the main part of the reverse osmosis process.

Then you have one or two post filters to improve the taste and odour and "polish" the water.

So if you have 3 prefilters, plus 1 membrane and 2 post filters that is a six stage RO (ie 3+1+2 = 6).

The thing to bear in mind is that Reverse Osmosis is a "yes or no process". You cannot have "light vs heavy RO".

Some RO manufacturers put on extra stages/filters because it sounds better. But to be honest, to filter mains water in a "developed" country, having more than 5 stages is overkill.

It's akin to a boy racer putting extra "go faster" stripes on his awe-inspiring car. It neither makes the young lad look cooler or go faster.

The other issue is that the manufacturers and dealers will get more money from you in the long term because you will need to change the pre and post filters - usually every 6 months.

(The membrane needs changing every 3 years - depending on local water quality).

The more stages, the more replacement RO filters you'll need to buy...

Our domestic RO unit is a 5 stage unit. You get two prefilters (which is more than enough), a membrane and two post filters

The second post filter is the remineralising / re alkalising filter. This stops the water being too acidic and also remineralises the water.

Unfortunately not many UK suppliers offer this important filter.

Their extra stages are often only more carbon filters which have almost zero effect on water that's already been filtered well. But it does sound good !

For full performance details click here

For information on High Flow / High Capacity Reverse Osmosis systems click here

Drink to your health

Our water filter systems can remove harmful pathogenic bacteria, cysts, parasites, and unhealthy chemical contaminants such as Chlorine, while at the same time leaving in the essential minerals your body needs.


Save money on bottled water purchases by regularly usingfiltered water. Get your highest quality water filters at the best price here.


We supply the widest range of water filters for any needs - residential or commercial.