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They solve different problems. A whole-house filter treats all the water coming into your home. A reverse osmosis (RO) system is usually a point-of-use unit under one sink, for drinking and cooking water.
What each one is tested for
- RO (NSF/ANSI 58): the standard covers point-of-use RO systems. TDS (total dissolved solids) reduction is a required claim. Optional claims include arsenic, lead, nitrate/nitrite, fluoride, chromium, perchlorate, cyst and VOC reduction. The standard also covers efficiency and recovery ratings.1
- Whole-house and other filters (NSF/ANSI 42, 53, 401): NSF/ANSI 42 covers aesthetic issues like chlorine, taste and odor. NSF/ANSI 53 covers specific health-related contaminants named in the product listing.2
Always check the exact listing. A certification covers only the claims listed for that model.1,2
Published cost ranges
| System | Published range |
|---|---|
| Point-of-use RO system | $150–$1,300 for the system; installation typically $300–$700, point-of-use installs usually $150–$300 (This Old House)3 |
| Under-sink RO, installed | About $200–$1,000 all-in, most jobs $300–$600 (Plumbing Picks)4 |
| Whole-house RO | About $1,000–$4,800 (This Old House)3 |
| Whole-house filtration, installed | $850–$5,400 on average (HomeGuide)5 |
| Under-sink filter, installed | $170–$580 (HomeGuide)5 |
These are national ranges. We haven't found a published local survey for any of our cities, so compare local quotes.
Which one fits your problem?
| Your concern | Usually the better fit |
|---|---|
| Chlorine taste or smell at every tap and shower | Whole-house carbon filter (look for NSF/ANSI 42) |
| Salty or mineral taste in drinking water, high TDS | Under-sink RO (NSF/ANSI 58 requires TDS reduction) |
| A specific health contaminant | A system certified for that contaminant: NSF/ANSI 53 filter or an NSF/ANSI 58 RO with that optional claim |
| Scale, spots, appliance wear | Neither. That's a softener's job. See filters vs. softeners. |
Why TDS matters
EPA's secondary standard for TDS is 500 mg/L. It's a non-enforceable guideline for taste, odor and appearance, not a health limit.6 Many Southwest homes on Colorado River water look at RO for that reason. See why Tucson's CAP water tastes the way it does.
Can you have both?
Yes. Many homes in hard-water areas pair whole-house treatment with RO at the kitchen sink. A salt-based softener runs $1,200–$3,800 installed (HomeGuide).7 Ask dealers whether a bundle costs less than buying separately.
More: whole-house filter cost · RO system cost · softener vs. RO
Sources
- NSF: NSF/ANSI 58 reverse osmosis systems
- NSF: NSF/ANSI 42, 53 and 401 filtration standards
- This Old House: reverse osmosis system cost (2026)
- Plumbing Picks: cost to install a reverse osmosis system (2026)
- HomeGuide: home water filtration system cost (2026)
- US EPA: secondary drinking water standards
- HomeGuide: how much does a water softener cost? (2026)
Last reviewed Oct 15, 2026. This is general information, not professional advice. Confirm figures with your utility and installer.