Choosing a home water filter often comes down to scope: do you want better water at every tap, or a dedicated solution for drinking and cooking? Whole-house (point-of-entry) and under-sink (point-of-use) systems each have distinct advantages. This comparison walks through how they differ, what they’re best for, and when homeowners combine both.
What Is Whole-House Water Filtration?
A whole-house system is installed at the point where water enters your home—typically on the main line after the meter or pressure tank. All water that flows through your plumbing passes through the system before reaching any faucet, shower, or appliance.
How it’s usually built: Most systems use one or more stages: sediment filtration (to catch particles and protect downstream components), followed by carbon or other media to improve taste, odor, and reduce certain chemicals (e.g., chlorine). Configuration depends on your water quality and goals.
Pros:
- Improved water at every tap—showers, laundry, dishwashing, and drinking.
- Protects plumbing and appliances from sediment and scale (when combined with softening if needed).
- Single installation point; no under-sink space required.
- Consistent experience throughout the home.
Cons:
- Higher upfront cost and more involved installation.
- May not remove dissolved minerals (hardness) or every contaminant; hard water often requires a separate softener or additional treatment.
- Maintenance (filter or media changes) is required on a schedule.
Best for: Households that want better-tasting water and less chlorine/sediment everywhere, and that are willing to invest in a single, comprehensive entry point.
What Is Under-Sink Water Filtration?
Under-sink systems treat water at one (or a few) locations—most commonly the kitchen faucet for drinking and cooking. They sit under the sink and feed a dedicated faucet or the main faucet via a diverter.
Types:
- Carbon block or granular carbon: Good for taste, odor, chlorine, and some chemicals; often certified to NSF/ANSI 42 and/or 53.
- Reverse osmosis (RO): Multi-stage system with a membrane; reduces a wide range of dissolved contaminants, including many that carbon alone doesn’t. Often certified to NSF/ANSI 58.
Pros:
- Focused on the water you drink and cook with.
- Generally lower cost and simpler installation than whole-house.
- RO, in particular, can reduce many dissolved contaminants (e.g., lead, arsenic, nitrates, PFOA/PFOS when certified).
- No impact on flow elsewhere in the house.
Cons:
- Only the faucet(s) connected to the system get filtered water.
- RO produces a concentrate stream (waste water) and requires filter and membrane changes.
- Under-sink space and plumbing access are required.
Best for: People who mainly care about drinking and cooking water, want strong contaminant reduction (e.g., RO), or already have acceptable water elsewhere and don’t want a full entry-point system.
Side-by-Side: Key Differences
| Factor | Whole house | Under-sink |
|---|---|---|
| Coverage | Every tap and appliance | Typically kitchen (or specific faucets) |
| Installation | Main water line | Under sink |
| Typical cost | Higher | Lower to moderate |
| Contaminant focus | Sediment, chlorine, taste/odor; some chemicals | Depends on type; RO can address many dissolved contaminants |
| Maintenance | Filter/media changes at entry point | Filter (and membrane for RO) at point of use |
| Space | No under-sink footprint | Uses cabinet space |
When to Use One, the Other, or Both
- Whole house only: Makes sense when your main concerns are taste, odor, chlorine, and sediment throughout the home, and you’re not targeting dissolved contaminants like lead or PFAS at the tap.
- Under-sink only: Makes sense when you only want better drinking/cooking water and are okay with unfiltered water elsewhere. Common for renters or those with limited budget or space.
- Both: Many homeowners use whole-house filtration for whole-home improvement (showers, laundry, appliances) and add an under-sink RO at the kitchen for an extra level of contaminant reduction and taste for drinking and cooking. This “layered” approach is popular where water quality concerns are broader and drinking water is a priority.
Cost and Maintenance (High Level)
- Whole house: Equipment and installation vary with size and complexity; filter or media replacement is typically once or twice a year, depending on water use and quality.
- Under-sink: Carbon systems need cartridge changes every 6–12 months; RO systems need pre/post filter changes and less frequent membrane replacement.
- Always follow the manufacturer’s schedule and use certified replacement parts to keep performance and certifications valid.
Bottom Line
Whole-house filtration improves water everywhere; under-sink (especially RO) focuses on high-quality drinking and cooking water at one location. Your choice should depend on your water quality, priorities (taste vs. contaminant reduction), budget, and whether you want whole-home coverage, a single-point solution, or both. Checking your water quality—via a utility report or a lab test for well users—helps narrow down the right type and level of filtration for your home.