How Do Home Reverse Osmosis Systems Work?

Reverse Osmosis is the most effective water filtration possible, the process uses pressure to force a solvent (such as water) through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side.

Best known for removing the salt from sea water to get fresh water (desalinisation) Reverse Osmosis is also used to purify naturally occurring fresh water for industrial and medical processes.

The applications of Reverse Osmosis include; drinking water purification, aquarium keeping, hydrogen production, dialysis and various applications within the food industry.

What does a home based Reverse Osmosis System consist of?
To be effective home installed Reverse Osmosis Systems typically have 4 - 5 stages, most of the complexity of these units relates to the pre filters that are in place to prevent the Reverse Osmosis membrane becoming clogged up and becoming degraded and therefore prolong the systems life. The stages of a typical home based Reverse Osmosis System are as follows:

1. Sediment Pre Filter used to extract the larger contaminants from the water including dust, dirt, sand, rust particles and grit where present.

2. Optionally a Secondary Carbon Pre Filter used to extract most of the chlorine and organic chemicals, providing enhanced reduction of taste and odour and helping to protect the RO membrane which is vulnerable to chlorine.

3. The Reverse Osmosis Membrane normally made from a thin film composite (TFC) membrane.

4. Optionally a Carbon Post Filter used to capture any chemicals still present and which will help against any tainting which may occur within the units water storage tank.

5. Optionally an ultra-violet lamp is used to disinfect the water of any microbes that may have escaped the reverse osmosis membrane.

Is Reverse Osmosis appropriate for everyone?
By it’s very nature Reverse Osmosis is a wasteful process flushing away up to 1/3 of the water that passes through the system. Reverse Osmosis is definitely not appropriate for everyone, in the UK most people enjoy food grade quality water 24/7, if you are supplied via the mains then it’s likely that your water is absolutely fine to drink, if the water has a poor taste/smell then you could consider a carbon based filtration system which is more cost efficient than Reverse Osmosis. Disturbingly many UK homeowners are being encouraged down the route of Reverse Osmosis with the promise of pure water despite the fact that the system is generally considered to be overkill in most instances. If you intend to source your water from a private supply, or are in any doubt about your water quality we strongly advise you to contact your local water authority.

What Contaminants Does Reverse Osmosis actually remove?
According to the manufacturer of our Reverse Osmosis System the following contaminates are removed from the household water supply. NB: We can find no machine on the market that guarantees to remove 100% of all contaminants:
Aluminium 96 - 98%
Ammonium 80 - 90%
Bacteria 99+%
Boron 50 - 70%
Bromide 90 - 95%
Cadmium 93 -97%
Calcium 93 - 98%
Chlorine 98+%
Chloride 92 - 95%
Chromate 85 - 95%
Copper 96 - 98%
Cyanide 85 - 95%
Fluoride 92 - 95%
Hardness 93 - 97%
Iron 96 - 98%
Lead 95 - 98%
Magnesium 93 - 98%
Manganese 96 - 98%
Mercury 94 - 98%
Nickel 96 - 98%
Nitrate 80 - 95%
Phosphate 95 - 98%
Potassium 92 - 96%
Silica 80 - 90%
Silver 93 - 96%
Sodium 92 - 98%
Sulphate 96 - 98%
Thiosulphate 96 - 98%
Zinc 96 - 98%

Why are Reverse Osmosis Systems used in the home?
There are 3 key reasons why home users wish to own a reverse osmosis system.

Your water supply is not mains connected and contains one of the listed contaminants (see above) that you wish to remove.

Many reef aquarium keepers use reverse osmosis to help produce their artificial mixture of seawater, this is because ordinary tap water often contains excessive levels of chlorine or other impurities detrimental to the sensitive organisms in a reef environment.

You require a water softener to protect your house from the effects of hard water and are conscious of your salt intake, Reverse Osmosis can be used to remove the salt from the water.