Whole-House Filter vs. Under-Sink Filter: Which Do You Need?
Point-of-entry vs. point-of-use. When to treat all the water in your home and when a single filtered tap is enough.
The real question is scope: do you want to treat all the water in your home, or just the water you drink? That is the difference between whole-house and under-sink filtration.
Choose a whole-house filter to treat every tap and shower, cut chlorine at the showerhead, and protect plumbing and appliances. Choose an under-sink filter for the most thorough drinking water at one tap, for much less. Many homes do both: whole-house carbon for the house, under-sink reverse osmosis for drinking.
Side-by-side comparison
| Factor | Whole-House Filter | Under-Sink Filter |
|---|---|---|
| Type | Point-of-entry (treats all water) | Point-of-use (treats one tap) |
| Covers | Every tap, shower, and appliance | The kitchen sink for drinking and cooking |
| Best at | Chlorine, sediment, taste across the home; protecting plumbing | Thorough drinking water; reverse osmosis removes dissolved contaminants |
| Removes dissolved contaminants (nitrate, arsenic)? | Not like reverse osmosis | Yes, if it is a reverse osmosis unit |
| Installation | At the main water line; often professional | Under the sink; frequently DIY |
| Upfront cost | Higher | Lower |
| Best for | Chlorine-free showers, whole-home protection | Drinking-water quality on a budget |
When whole-house is the answer
If you want filtered water everywhere, not just at the kitchen sink, a whole-house filter is the only option that delivers it. It reduces chlorine at every showerhead (which matters for skin and hair), removes sediment that can wear on fixtures and appliances, and improves taste at every tap. It is installed at the main line where water enters your home, usually by a plumber. See our whole-house filter guide. Note that a whole-house carbon filter is not reverse osmosis, so for dissolved contaminants you still want a point-of-use RO for drinking.
When under-sink is enough
If your priority is the water you drink and cook with, an under-sink filter gives you more thorough results at the tap for a fraction of the cost of whole-home treatment. An under-sink reverse osmosis system removes dissolved contaminants like nitrate, arsenic, and fluoride that a whole-house carbon filter cannot. It installs under the kitchen sink and leaves the rest of your plumbing untreated. See our under-sink guide and under-sink vs. pitcher.
Do you need both?
Plenty of homes do. A common setup is a whole-house carbon filter for chlorine and sediment across the home, plus an under-sink reverse osmosis system for the most thorough drinking water. If hardness and scale are your real problem, note that neither of these softens water, so start with softener vs. filter. And whatever you choose, check your city's data so you treat the contaminants you actually have. Compare specific systems in our side-by-side comparisons.
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Under-sink system — thorough drinking water at the kitchen tap
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