Reverse osmosis water filters have many advantages and a few significant disadvantages. Read our guide to help you choose the best reverse osmosis water filter for home use.
Reverse osmosis, the good, the bad and the ugly!
In your search for the best water filters for home use you will encounter a vast array of filtration methods and manufacturers. One of the most common of these is the reverse osmosis filtration system. Many people love it and many people dislike these filters.
Very few doubt its efficiency and this may be the problem. This system removes minerals that naturally occur in water and are a vital part of the health benefits of drinking water.
Is the trade-off between removing impurities and removing vital minerals worth it? You'll have to make up your own mind. Read on to get more information on how these types of filtration systems work as well as the advantages and disadvantages of a reverse osmosis water filter.
What is reverse osmosis?
The thinking behind reverse osmosis(RO) came about due to the needs of the printing and imaging industry for water without minerals.
The logic of the filtering process was then applied to developing water filters for home use.
In very basic terms it is a system that filters water by forcing that water, at high pressure, through a very fine material known as a semi-permeable membranne. The water is usually filtered before it reaches the membrane and after the membrane
This filter is referred to as semi-permeable as it does not let everything pass through it. Most sources of contamination have a larger molecular structure than water so the water passes through and most of the contaminants are left behind.
Reverse osmosis is very effective at removing contamination such as arsenic, chlorine, fluoride, sediment, iron, bacteria, viruses, heavy metals, nitrates, many microorganisms, bad tastes and odor.
All Reverse osmosis systems share the same basic process. However, there is a significant difference between the basic and the more advanced versions of this type of water filtration system.
The filtering process
Step 1 A valve is attached to your cold water supply line. A tube then goes from the valve to the filter. before it reaches the semi-permeable filter it pass through another filter.
This is known as pre-filtering.This stage of the process removes sediment and dirt. A more advanced system might use a carbon pre-filter which would remove Chlorine.
Step 2 The water has now passed through the first filter and goes through the reverse osmosis membrane. As it passes through this second filter most of the contaminants are removed.
Step 3 The cleaner water now flows into a storage tank. The storage tank contains an automatic shut-off valve. When the tank is full of cleaner water this valve is activated and no more water is let pass through the RO membrane.
Step 4 A water faucet comes with the reverse osmosis water filter and this is mounted on the sink separate to any other faucets.
Step 5 Turning on the RO faucet activates the next stage of filtration. When this happens the water leaves the water storage tank and passes through another filter on its way towards the faucet. This is know as post-filtration. This step removes any lingering odor or taste.
Basic and advanced reverse osmosis water filters
As with most things, this system is only as good as the quality of its components and how they are set-up. The types of pre- and post-filter cartridges used as well as the type of reverse osmosis membrane will greatly affect the results.
Pre- and post filter cartridges
There are 3 stage filter and 4 stage reverse osmosis water filter systems and there are also 2 types of reverse osmosis membranes.
A 3 stage filter system uses either a sediment filter or a combination filter of a sediment and activated carbon filter. The activated carbon filter deals with the Chlorine that is added at water treatment faciliies.
A 4 stage filter system employs 2 pre-filters. One filter specifically for sediment filtering and the other for Chlorine and chemical filtering
Types of reverse osmosis membranes
Cellulose Triacetate (CTA)membranes and Thin Film Composite (TFC) membranes. TFC provides better filtration than CTA but if TFC reverse osmosis membranes are used they need an activated carbon pre-filter to remove the Chlorine before it reaches the membrane. This type of membrane gets quickly destroyed by chlorine and an activated carbon pre-filter is essential.
Which is the best reverse osmosis water filter system?
It has to be the 4 stage filtering system using the TFC reverse osmosis membrane. Depending on useage and the quality of water going into the system the cartridges should last approximately six months. The reverse osmosis membranes can survive for several years depending on useage.