Stages involved in the reverse osmosis process

What do the various stages do in a reverse osmosis system?

It is in your best interests to spend some time deciding how much water you require per day when it comes to choosing your Reverse Osmosis Water Filter, for example how many people will be using the system, are you going to use the water for cooking purposes, are you going to hook up a supply line to your fridge, how much water will be required in the warmer months. The reason for this is that Reverse Osmosis Systems are very slow and require a holding tank to store the water in. There are many sizes of tank available, we can supply 12, 16, 25, 35, 50 or 75 Litre tanks. We supply a 12 Litre tank as standard as this tank is generally suitable for a family of 4 and will fit under most kitchen sinks.


How long do you have? Dr Oz from Oprah states that he has difficulties understanding Reverse Osmosis and he has performed open heart surgery!

Systems can come in 3, 4 or 5 stages any more than this is overkill and may be more based on marketing hype than performance.

Here are the basics of a 5 Stage Reverse Osmosis Water Filtration System:


Sediment filter

Removes suspended matter such as silt, rust sand, algae, sediment, scale particles,

dirt and cloudiness from the water (requires replacement every 12 months).

Stage 2

Carbon Cartridge

Removes herbicides, pesticides, chlorine, chlorine bi-products and organic

chemicals to protect the membrane (requires replacement every 12 months).

Stage 3


 Removes 98% of impurities including the organic and in-organic chemicals.

Such as FLOURIDE!!! In a low waste system this will produce 1 litre of pure water and

send 1 litre of water to drain, this may go as high as 1 litre of pure water sending 2-3

litres of water to drain. (requires replacement every 3 - 6 years).

Stage 4

Carbon Post Filter

Polishes the water and removes any taste or odour water may have picked up while

sitting in the tank, (requires replacement every year).

Stage 5

Varies depending on system, may be another carbon filter, a deioniser or a remineralsier. In the case of our 5 stage system we use a natural calcite remineraliser which balances the pH and as the name suggests adds natural minerals into the water.


As in diagram above water is taken from your cold water connection under the sink and is then fed into the first stage sediment filter, it is then fed through the second stage carbon filter before being squeezed through the reverse osmosis membrane, anything that cannot pass through the membrane is sent to waste, this will require a connection to your existing drainage under the sink, the pure water is then sent to the holding tank, once this tank is full and automatic shut off valve will stop the production of water. When the drinking water tap is opened, the water from the tank passes through a carbon filter before providing the user with clear pure water on tap. There is only one connection on the holding tank which allows water to flow in both directions.

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