Filtered water pouring into a glass tumbler on a kitchen counter

Whole-House vs. Under-Sink Water Filtration: Which Do You Need?

Whole-house filtration treats every drop entering your home; under-sink systems perfect the water you actually drink. They solve different problems — and the right answer for many homes is one, the other, or both. Here’s a practical way to decide without overbuying.

The core difference: point of entry vs. point of use

A whole-house (point-of-entry) system installs where the water line enters your home, so showers, laundry, water heater, and every faucet receive treated water. An under-sink (point-of-use) system installs at one location — almost always the kitchen — and typically uses reverse osmosis to bring drinking water to the highest purity level.

What each one is best at

Choose whole-house when the problem touches your whole home

  • Chlorine taste and odor everywhere — including showers, where chlorine vaporizes.
  • Sediment that clogs fixtures and wears out appliances.
  • Iron and manganese staining on fixtures and laundry — common on wells; iron is a nuisance contaminant that also fouls downstream equipment (USGS).
  • Hardness (scale on fixtures, dry skin) — solved by a softener, often paired with filtration in a combo system.

Choose under-sink RO when the concern is what you swallow

  • Lead, arsenic, nitrates, PFAS, fluoride, total dissolved solids — dissolved contaminants that carbon-only whole-house systems don’t reliably remove.
  • Taste for drinking and cooking — RO delivers bottled-quality water on tap for a fraction of bottled cost.

Why “both” is often the right answer

The two systems protect different things: whole-house protects your home and skin; RO protects your drinking water. A common, cost-effective setup is a whole-home carbon/sediment system (plus a softener on hard water) with a compact RO at the kitchen sink. The whole-house stage also acts as pre-treatment that extends the life of the RO membrane. Compare options in our whole-home filtration and under-sink RO collections.

A 3-question shortcut

  1. Is the problem visible on fixtures, laundry, or skin? → whole-house.
  2. Is the problem in a lab report or utility notice (lead, PFAS, nitrates, arsenic)? → under-sink RO.
  3. Both? → pair them.

City water users can pull the utility’s annual water quality report; well owners should test yearly at minimum (CDC). If you want a second pair of eyes, our free water analysis is exactly that, or answer four questions in the Find Your System quiz for an instant recommendation.

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