Reverse osmosis is one of the most effective water treatment technologies available — but it is not the right solution for every well water problem. Here is what RO removes, what it doesn't, and how to decide if it makes sense for your situation.
| Contaminant | RO Removal Rate |
|---|---|
| Nitrates | 85–95% |
| Arsenic (As5+) | 90–95% |
| Lead | 95–99% |
| Fluoride | 85–92% |
| Dissolved solids (TDS) | 90–99% |
| Radium | 85–95% |
| Barium | 85–95% |
| Bacteria (with membrane intact) | 99%+ |
Point-of-use (under sink): $200–$500. Treats drinking and cooking water only. Most practical for the vast majority of households. Produces 50–75 gallons per day — more than enough for drinking and cooking.
Whole-house RO: $1,500–$5,000+. Treats all water in the home. Only necessary when contaminants pose skin exposure risks (some industrial VOCs, high arsenic) or when the entire household water supply is compromised. Produces significant wastewater.
A point-of-use RO system requires:
RO is the right choice when you have nitrates above 10 mg/L (especially with infants), arsenic above 10 μg/L, lead concerns, elevated total dissolved solids affecting taste, or multiple dissolved contaminants that would otherwise require several separate treatment systems. It is the most versatile drinking water treatment available.
Pre-treat iron before RO. High iron water (over 0.3 mg/L) clogs RO membranes rapidly and dramatically shortens their lifespan. If your well has iron, install a sediment pre-filter and consider an iron filter before the RO system.
RO does not effectively remove volatile organic compounds (most pass through unless pre-filtered with carbon), dissolved gases like hydrogen sulfide, radon, and CO2, chlorine/chloramines (which damage the membrane), or high levels of particulate iron (which clogs the membrane rapidly).
Point-of-use (under-sink) systems cost $200-$500, treat drinking and cooking water only, and are practical for most households, producing 50-75 gallons per day. Whole-house RO ($1,500-$5,000+) is only necessary when contaminants pose skin exposure risks, like some industrial VOCs or high arsenic.
A point-of-use RO system needs pre-filters replaced every 6-12 months ($30-$60), the RO membrane replaced every 2-3 years ($40-$80), and the post-filter replaced annually ($15-$30) — totaling about $50-$100 per year.
RO does reduce hardness, but it's not the cost-effective solution for that purpose — a dedicated water softener handles hardness much more efficiently and affordably.
RO is the right choice when you have nitrates above 10 mg/L, elevated arsenic, lead, or fluoride, or generally high dissolved solids — contaminants it removes at 85%+ rates. It's not the answer for gas-based problems like hydrogen sulfide or radon.
Use our free decoder to understand what your well water test results mean.
Use the Free Decoder →