The 4 stages of water filtration system are:
1st PP, sediment:
To eliminate the rust and silt that affects the taste and appearance of your water.
2nd Activated Carbon:
It reduces chloramines, chlorine and other materials that cause bad taste and odors.
3rd 50/75/100 GPD RO membrane:
The membrane will effectively reduce TDS, total dissolved solids, Sodium and a wide range of contaminants such as Lead, Arsenic, Perchlorate, Chromium, Copper and Radium.
4th Post Carbon:
A high quality carbon filter, which filters water after the membrane.