Reverse osmosis (RO) is a water purification process in which water is forced through a semi-permeable membrane that removes
90-99% of tap water impurities. The result is water that is free of minerals and other contaminants.

What does it remove? Rejection Characteristics Of Reverse Osmosis Membranes:
Sodium 85 - 94%
Sulfate 96 - 98%
Calcium 94 - 98%
Potassium 85 - 95%
Nitrate 60 – 75%
Iron 94 – 98%
Zinc 95 – 98%
Mercury 95 – 98%
Selenium 94 – 96%
Phosphate 96 – 98%
Lead 95 – 98%
Arsenic 92 – 96% *
Magnesium 94 – 98%
Nickel 96 – 98%
Fluoride 85 - 92%
Manganese 94 – 98%
Cadmium 95 – 98%
Barium 95 – 98%
Cyanide 84 – 92%
Chloride 85 – 92%

The removal percentage will vary based on membrane type, water pressure, water temperature and total dissolved solids.
Activated carbon filtration that accompanies a reverse osmosis system will also remove below:
Chlorine 99.9%
VOCs (volatile organic compounds) 99.9%
Trihalomethanes (byproducts of chlorination) 99.9%
Pharmaceuticals 99.9%

*Results not guaranteed based on various water conditions.