We now have an understanding of the working of the membrane that allows osmosis to take place. The next step is to understand how this technology can be applied to filtering tap water. 

Reverse Osmosis water filter uses a pressure pump to force osmosis to happen in the opposite direction.

                                            
This has proven to work! It requires a substantial amount of energy for operation and produces anywhere between 4 – 6 glasses of wastage water per glass of purified water. In some countries this has been a very effective method to purify water that may contain viruses which cannot be removed by micron filtration systems. 

The membrane will need to be replaced every so often based on the usage and quality of tap water. Overall it is an expensive technology but is life saving in areas where treated municipal water is unheard of. 

The water produced from a Reverse Osmosis water filter unit is completely stripped of all its contents, which includes trace minerals such as Calcium, Magnesium etc. which are essential for our body.
If our municipal water is treated for microbial growth using different methods – the common being Chlorination, our main concern for in-home filtration would be removal of these Chemicals as well as heavy metal deposit which could have taken place due to the age old pipes that bring water to our homes.

Activated Carbon is the most effective method of removing Chlorine, heavy metals and other Chemicals. In addition to the Carbon filter, a micron filter can be used to remove sediments.