Home Water Filters Explained: What Removes What
There is no single best water filter, only the right filter for a specific contaminant. This guide maps the main technologies to what they remove so you can choose based on your water, not marketing.
Walk down the water-filter aisle and you will see pitchers, faucet attachments, under-sink systems, and whole-house units, all promising cleaner water. The marketing rarely tells you the one thing that matters: different filters remove different contaminants, and none removes everything. The right filter depends entirely on what is in your water.
Start with what is in your water
Before choosing a filter, find out what you are trying to remove. Read your utility’s annual report, covered in how to read your water quality report, or run a test, covered in how to test your drinking water. Buying a filter without knowing your water is like buying medicine without a diagnosis; you might get lucky, or you might treat the wrong problem.
The main filter types
- Activated carbon (pitchers, faucet, under-sink): adsorbs chlorine, taste and odor, many organic chemicals, and, in quality carbon blocks, lead and some PFAS. See activated carbon filters.
- Reverse osmosis (under-sink): pushes water through a fine membrane and removes the broadest range, including lead, arsenic, nitrate, PFAS, and dissolved salts. See reverse osmosis.
- Distillation: boils and re-condenses water, removing minerals, metals, and many chemicals. See distillation.
- UV disinfection: inactivates bacteria and viruses but removes no chemicals. See UV purification.
- Ion exchange / softeners: swap ions to soften water or remove specific contaminants like nitrate.
Matching filter to contaminant
| Contaminant | Effective methods |
|---|---|
| Chlorine, taste, odor | Activated carbon |
| Lead | Carbon block certified for lead, reverse osmosis, distillation |
| PFAS | Reverse osmosis, certified carbon, ion exchange |
| Arsenic | Reverse osmosis, specialized adsorptive media |
| Nitrate | Reverse osmosis, ion exchange, distillation |
| Bacteria, viruses | UV, boiling, reverse osmosis (with the right membrane) |
Why certification matters
A filter only removes what it is independently certified to remove. Look for certification to NSF/ANSI standards, which test real performance: Standard 42 for taste and odor, Standard 53 for health contaminants like lead, Standard 58 for reverse osmosis, Standard 55 for UV, and Standard 401 for emerging contaminants. A claim of "reduces lead" without certification is just a claim. Always match the certification to the specific contaminant you care about, not just the brand name.
How to pick
Decide what to remove, choose a technology certified for it, and then pick a format that fits your home and budget, from a simple pitcher to an under-sink reverse osmosis system. For a structured walk-through of that decision, see how to choose a water filter. The goal is not the most expensive or most powerful filter; it is the one matched to your actual water.