Reverse osmosis systems
Reverse osmosis is the most thorough treatment for dissolved contaminants — but it's usually a point-of-use fix for drinking water, not a whole-house system. Here's when it's the right tool.
Reverse osmosis treats one tap and wastes some water doing it. It's the right call for nitrate, arsenic, and high TDS — not for whole-house scale or a sulfur smell. For those, see whole-house systems.
Where reverse osmosis fits
Under-sink reverse osmosis
The most thorough option for nitrate, arsenic, lead, and TDS at one tap. Tank, tankless, or neither.
See picks →Whole-house reverse osmosis
A $3,000–$8,000 specialist system most homes don’t need. When it’s worth it, and the cheaper fix.
Do you need it? →Countertop reverse osmosis
No drilling, no drain — plug it in and pour. Which portable units are actually NSF certified.
See picks →Install it yourself
The under-sink install, step by step: feed valve, drain saddle, faucet, and the startup flush.
How-to guide →Confirm it first
Reverse osmosis is overkill for taste alone. Test before you buy.
Testing guide →