Reverse osmosis, or RO, is simply the best way to clean your water for both homes and businesses. A good RO system pushes water through a special membrane. This membrane has tiny holes that stop dissolved salts, heavy metals, and organic stuff, but let pure water molecules pass right through. What you get is super clean water, with 95-99% of total dissolved solids gone. Here are the top 10 contaminants RO systems remove, why they matter, and how well RO gets rid of them.
1. Lead
Typical RO removal rate: 97-99%
Lead gets into our drinking water from old lead pipes or solder, especially in buildings built before 1986. For kids, there’s no safe amount of lead in drinking water. RO membranes certified to NSF/ANSI Standard 58 for lead reduction offer the most reliable protection right at your tap.
2. Arsenic
Typical RO removal rate: 92-96%
Arsenic naturally shows up in groundwater across the western US, New England, and the Midwest. If you’re exposed to arsenic levels above the EPA’s limit of 10 ppb for a long time, it’s linked to skin, bladder, and lung cancers. Carbon filters and water softeners don’t remove arsenic. RO is the most recommended technology for getting rid of arsenic at the point of use.
3. Fluoride
Typical RO removal rate: 85-92%
Cities add fluoride to water, usually at 0.7 ppm, to help with dental health. But some people prefer to cut down on their fluoride intake for personal reasons. Carbon filters don’t remove fluoride; RO is the right system for homes that want to reduce it.
4. Nitrates
Typical RO removal rate: 83-92%
Nitrates from farm fertilizers, septic systems, and animal waste can seep into groundwater and surface water. The EPA says nitrates shouldn’t be above 10 mg/L. Levels higher than that can cause a serious condition in babies under 6 months old called methemoglobinemia. RO is one of the few point-of-use technologies that can bring nitrate levels down to safe amounts.
5. PFAS Compounds
Typical RO removal rate: 90-99%
PFAS, which includes PFOA, PFOS, and similar chemicals, has contaminated water supplies near military bases, airports, and factories all over the US. In 2024, the EPA set the first federal limits for PFAS at 4 parts per trillion. RO membranes block PFAS at 90-99%, making them the most effective home defense against these compounds.
6. Chlorine and Chloramines
Typical RO removal rate: 98-99% via carbon pre-filter stage
Water companies add chlorine and chloramines to disinfect water. But these can create harmful byproducts like trihalomethanes and haloacetic acids when they react with organic matter. A multi-stage RO system with a carbon pre-filter removes both the main disinfectants and these byproducts.
7. Chromium-6
Typical RO removal rate: 85-95%
Hexavalent chromium is an industrial pollutant that became famous because of the Hinkley, California water contamination case. At high concentrations, it’s a known human carcinogen. RO is one of the few point-of-use systems that really makes a difference in reducing chromium-6.
8. Bacteria and Viruses
Typical RO removal rate: 99.9% for bacteria; 99%+ for viruses with UV post-treatment
RO membranes have pores about 0.0001 microns big. That’s small enough to physically block bacteria and most viruses. If you add UV post-treatment to your point-of-use RO, you get great protection against microbes, which is super helpful during boil-water advisories for common contamination.
9. Total Dissolved Solids
Typical RO removal rate: 95-99%
TDS is just a fancy way of saying all the dissolved minerals, salts, and metals in your water. RO can drop TDS from 300-1,000 ppm in typical city water down to less than 50 ppm. Low TDS water tastes better and helps prevent scale buildup in your appliances.
10. Pesticides and Herbicides
Typical RO removal rate: 95-99%
Farm runoff can bring things like atrazine, simazine, and other regulated pesticides into surface water. RO membranes stop most organic pesticides and herbicides at rates over 95%, giving you consistent protection no matter how much these chemicals are in your source water.
