In our opinion, the best technology for home or office applications served by municipal water utilities is a combination of high quality carbon and sub-micron filtration. One of the best examples of this technology that we’ve found is the ispring RCC7 system which offers:
- Simple installation,
- Dedicated faucet, (take back your fridge!)
- Minimal maintenance
- Visual filter change indicator and
- Reduction of harmful contaminants to NSF/ANSI permissible limits, without removing healthy minerals.
To understand how reverse osmosis works, it helps to understand the process of osmosis which is ubiquitous in nature. When two solutions having different dissolved mineral concentrations are separated by a semi-permeable membrane, water flows from the less concentrated solution to the more concentrated solution. Examples of semi-permeable membranes are cell walls of a living organism, the membrane on the inside of a chicken egg, the intestinal lining of mammals, or man-made materials (type of plastic) which demonstrate this characteristic.
Osmotic pressure is a measure of how badly the water wants to go from the “clean” side to the “dirty side” (low mineral to high mineral content side of the membrane) and that is governed by the mineral concentration differential. This pressure can be surprisingly high and accounts for one mechanism used by trees to move water from the deepest root to the tallest limb, frequently a vertical distance of 100 or more feet. As water moves through the membrane, most minerals it contains are left behind.
The mechanisms which enable the water molecules to pass through the membrane leaving most of the dissolved minerals (ions) behind are not fully understood but it is definitely much more complex than simple filtration. Diffusion and active transport are models which play a role. One definition calls osmosis “the migration of water molecules across a membrane caused by the attraction of the dipole moment of water molecules to ions and polar molecules on the other side of a membrane.”
Reverse osmosis systems utilize man-induced pressure on the “dirty side” (high mineral content side) to overcome the natural osmotic pressure trying to flow the other way, plus some added pressure to speed the process in order to force water across the semi-permeable membrane to the “clean side”. In the RO process, 98% or more of the dissolved minerals are left behind on the “dirty side”.