Just How Does Reverse Osmosis Work?

How does reverse osmosis work? If you can grasp the idea, you will realize that, except in very rare occasions, a whole house reverse osmosis water treatment system is just a waste of money. And in this economic climate you need to hold onto all the cash you can for a rainy day. First, what is osmosis? It is defined as the movement of a solvent through a semipermeable membrane into a more concentrated solution until the concentration is the same on both sides. Water is known as the universal solvent. A semipermeable membrane will allow some molecules to pass, but not others. For example, cell walls are semipermeable membranes. Another example would be Gore-tex fabric. It contains a thin plastic film with minute pores. The pores are large enough to allow water vapor out, but small enough to prevents water from entering.

The semipermeable membrane allows passage of water molecules but not the salt that is dissolved in the water. The water will continue to cross the membrane until the salt concentration is the same on both sides of the membrane. When equilibrium is reached osmosis will stop.

By adding pressure to reverse the osmotic process the membrane becomes an extremely fine filter. Salty water is placed on one side and the pressure squeezes the water molecules through. This leaves the salty side even more salty, but only pure water on the other side. It takes a lot of pressure to do this and the process is slow. Did you ever wonder why we cannot drink salt water to survive? It is because of osmosis. When you put salty water in your stomach, osmotic pressure tries to dilute the salt by pulling water from your body. This causes severe dehydration, and eventually, death.

Hopefully, this cleared up the question: How does reverse osmosis work? There are many commercial applications for which reverse osmosis is vital. And whole house reverse osmosis applications are also found. But there are serious down sides to using this type of filtered water. The water is acidic because the alkaline minerals are removed. And drinking this type of water can be dangerous because it takes calcium and other essential minerals from bone and teeth to neutralize the acidity.

Besides the health issues of the water produced, there are many other issues to figure out if a whole house reverse osmosis filter is to be installed. The sizing of the unit depends, not only of the amount of water that you use, but how much water pressure you have and the temperature of the water. Reverse osmosis is very slow. And it is even slower when the pressure is low and the water is cold. That may require a large holding tank. The tank will need to be sanitized with chlorine on a regular basis. If water has all of the minerals removed, as it does with a whole house reverse osmosis product, it can become corrosive. The manufacturers get around this by using a calcite contactor (a tank with limestone that will dissolve into the water) to make it less corrosive.

So, you pay to take all the minerals and contaminants out of the water with a whole house reverse osmosis system, and then add back bleach and limestone. Wow, that does not make much sense. The idea is to have clean healthy water. There are better choices out there for excellent water filtration, that leave in the healthy minerals and remove unwanted pollutants.