Total 4 stages of RO system

without booster pump; with or without tank

With Sediment filter

With Carbon Block filter 

with 50GPD RO membrane 

With Post line filter 

STAGE 1: 
(SED; 5 Micron Sedimentary Filter)
Sediment Removal / PP Commercial grade sediment filter. Sediment filtration extracts suspended sediment, dirt, rust, silt and sand ranging from filtration of 20 microns down to 5 microns. Reduces particles 8 times smaller than what the naked eye can see. 

STAGE 2: 
(CCB; 1 Micron Coconut Carbon Block for Chemicals)
Carbon Block Filter / CTO High efficiency pre-filter removes Chlorine, then reduces or entirely removes Pesticides, Nitrates, Herbicides, tastes, odor, and disinfection by-products (chloramines, THM, TCE), Volatile Organic Compounds (V. O. C). 
STAGE 3: 
( Reverse Osmosis Membrane)
Reverse Osmosis Membrane This semi permeable membrane filters and rejects tiny impurities down to 1/10, 000th of a micron removing at least 95% of all impurities such as colloid, heavy metal, dissolved solids, germs and other harmful substances. Virtually only water molecules and dissolved oxygen can pass through the Reverse Osmosis Membrane. The rejected contaminants are flushed to drain. The product water is the extremely pure, crisp healthy drinking water. 
STAGE 4: 
(PC; Post Carbon Final polishing filter for taste and odor)
Post Activated Carbon Filter / T33 This carbon filter does an excellent job of "polishing" any dissolved solids that although unlikely, may have slipped through the 95% removal rate of the Reverse Osmosis Membrane and also through the DI Resin Bead Stage to give added assurance that you are getting the highest quality drinking water possible. The Final Polishing Filter also adds the mineral charcoal back into your water which helps to give the water a full bodied taste and also helps your body to detoxify.