How Does Reverse Osmosis Work?
What is the Reverse Osmosis Process?
Simply put, water pressure from your water supply forces water molecules through a very fine membrane leaving contaminants behind which are flushed down the drain.
The pores in a reverse osmosis membrane are between 0.0001-0.0005 µm (one-ten-thousandth to five-ten-thousandths) microns in diameter, which is only slightly larger than individual water molecules. Using your house water pressure, water molecules are forced through these microscopic pores, leaving behind a myriad of contaminants, too large to pass through. This purified water or "permeate", is stored in a holding tank, while the water that didn't pass through the membrane, containing a higher concentration of contaminants, is flushed down the drain.
Stages of Filtration- What is Reverse Osmosis?
Reverse Osmosis systems for home drinking water are units that consist of several filters. Depending on the system you chose, there is either one, two, or three prefilters that will filter the incoming water. This filtration takes place before the water is filtered through the RO membrane. After the RO filter, the purified water is then stored in the pressurized holding tank.
Usually, there is at least one pre-filter (before the RO membrane) in the system - an activated carbon filter, which removes chlorine and other chemicals. This pre-filter helps to prevent fouling of the RO membrane filter. On some RO systems, there are sometimes two pre-carbon filters.
Note: Activated carbon: means that the carbon filter has been chemically treated to improve its adsorption properties and filtration capacity.
There are RO systems that are well adapted for water wells. In these Reverse Osmosis Systems, the first filter is a sediment filter. The sediment filter removes rough particles, sand, dirt, rust, and silt. This helps keep the subsequent filters from fouling too quickly. The second stage is either one or two carbon pre-filters.
After passing through the pre-filters (before the RO membrane), and also passing through the RO membrane, the purified water is then stored in the holding tank.
When someone opens the counter-top RO tap, the pressurized holding tank forces the purified water through yet another carbon filter. This filter is called the post-filter (after the RO membrane), also known as a "polishing" filter. This activated carbon filter removes any tastes or odors the RO water may still have. This last filter gives your drinking water a final polish, removing any lingering impure smells or tastes.
The result is pure, healthy, and clean tasting water, free of chemicals and other contaminants!
Use Reverse Osmosis Filtration at Home for Pure Water - Video
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Note: If you have a refrigerator with an ice-maker and water dispenser, it's highly recommended that you tee into the supply line between the polishing filter and the counter-top tap of your Reverse Osmosis System. This way you can have your 'fridge dispensing ice-cubes and water with the same crisp and clean RO filtered water!
Visit our Particle Size Chart Page for more discussion on the sizes of contaminant particles, and understanding the filters that will successfully eliminate them.