Water equipment
Best Reverse Osmosis Systems
Reverse osmosis (RO) pushes water through a semi-permeable membrane fine enough to block dissolved solids most carbon filters can't touch — including a large share of sodium, nitrates, fluoride, and heavy metals. Here's how to pick a system and how the top-rated ones stack up.
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Quick picks
We are still verifying product picks for reverse osmosis, and we only list products after an editor has checked them. Until then, here is how to build a shortlist that fits your home.
- Certification. NSF/ANSI 58 is the standard for reverse osmosis systems. Check which contaminants the specific model is certified to reduce.
- Wastewater ratio. RO sends water to the drain as it filters. Compare stated drain-to-product ratios; permeate pumps and newer designs can cut waste.
- Tank or tankless. Tank systems need under-sink space; tankless models are compact but need power and adequate incoming pressure.
- Remineralization. RO strips most minerals. Some systems add a remineralization stage if you care about taste.
Full comparison
Our product comparison for reverse osmosis fills in as products are reviewed. These are the criteria we compare on, so you can check any model against them yourself.
| What to compare | What to look for |
|---|---|
| Certification | NSF/ANSI 58 is the standard for reverse osmosis systems. Check which contaminants the specific model is certified to reduce. |
| Wastewater ratio | RO sends water to the drain as it filters. Compare stated drain-to-product ratios; permeate pumps and newer designs can cut waste. |
| Tank or tankless | Tank systems need under-sink space; tankless models are compact but need power and adequate incoming pressure. |
| Remineralization | RO strips most minerals. Some systems add a remineralization stage if you care about taste. |
| Replacement schedule | Pre- and post-filters are usually yearly and the membrane every few years; confirm the intervals and part costs. |
What RO removes — and what it doesn't
A well-maintained RO membrane typically rejects 90–99% of total dissolved solids, which is why RO water tests near the bottom of any TDS chart. It's effective against many heavy metals, nitrates, and most dissolved minerals — including the calcium and magnesium that make water "hard."
What it strips out along with the contaminants is nearly all the mineral content too, which is why some households remineralize RO water afterward, and why RO waste ratios (the gallons of reject water per gallon produced) are worth checking — older 3:1 systems waste far more water than modern 1:1 tankless designs.
Under-sink vs. tankless RO
Traditional under-sink RO systems store filtered water in a pressurized tank, delivering water on demand without waiting. Newer tankless designs filter on demand instead — no tank means a smaller footprint and often a better waste-water ratio, but flow rate can be lower during heavy use. Either works well for kitchen-tap drinking water; whole-home RO is far less common and considerably more expensive to run.
Frequently asked questions
Does reverse osmosis remove all minerals?
It removes the large majority of dissolved minerals along with contaminants — RO water typically has a very low TDS. Some systems add a remineralization cartridge afterward if you want the mineral content back for taste.
How much water does an RO system waste?
It varies by design. Older tank-based systems commonly run a 3:1 or 4:1 waste ratio; many newer tankless systems are closer to 1:1. Check the manufacturer's stated ratio before buying if water waste matters to you.
How often do RO membranes need replacing?
Pre-filters typically need changing every 6-12 months; the membrane itself usually lasts 2-3 years under normal use, though local water quality and usage volume shift this significantly.
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