Whole-house vs under-sink water filter

Where should the filter actually go?

Stasis Home ResearchEvery claim on this page is graded against peer-reviewed health research and linked to its primary source.Updated July 2026

A whole-house filter and an under-sink filter solve different problems, so the honest answer is usually not one or the other. Point-of-entry carbon is the only filter that reaches your shower and bath, where much of your chlorine-byproduct dose is breathed in. Point-of-use is where you get drinking-grade removal for lead and PFAS. Match each to its exposure point.

How they differ

The two filters are named for where they sit in the plumbing, and that placement decides what each can reach. A point-of-entry system treats water where the main line enters the house, so every tap, shower, and appliance downstream runs through it. A point-of-use system treats one fixture, almost always the kitchen cold line, right before the water reaches your glass. Whole-house carbon's advantage is coverage: it is the only filter that touches the shower and bath, where volatile chlorination byproducts go airborne and a real share of your dose is inhaled and absorbed through skin rather than swallowed. Its limit is that it is not drinking-grade removal. It sits upstream of your own brass fixtures and pre-1986 solder, so it never sees the lead those add, and its carbon bed can release captured PFAS once it saturates. Point-of-use is where contaminant removal for what you drink actually happens, either a certified carbon block or, for the full dissolved range, reverse osmosis.

Side by side

How Whole-house carbon and Under-sink carbon handle each concern.
Concern	Whole-house carbon	Under-sink carbon
Chlorine byproducts, shower and bath route	YesThe one real edge of point-of-entry. Showering can raise indoor-air chloroform more than 40-fold, and a share of your lifetime dose arrives through breath and skin, not the glass (Gordon et al., 2005; Maxwell et al., 1991). A tank at the entry is the only filter that reaches that water.	NoA kitchen filter treats the tap you drink from and never touches the shower or bath. It does remove these byproducts from what you drink and cook, but the inhaled and dermal route in the bathroom runs unfiltered.
Lead	NoLead is added by your home's own brass fixtures and pre-1986 solder, which sit downstream of where a point-of-entry tank lives. The tank never sees that lead, so it cannot remove it.	YesA point-of-use fix by nature. A block certified to NSF/ANSI 53 for lead demonstrates 99% reduction in testing, and it sits right where water picks up fixture lead before you pour it.
PFAS	NoNot the primary move, and it can backfire. In a 73-home field study, whole-house systems were widely variable and some raised PFAS in the treated water as the carbon bed saturated and released what it had captured (Herkert et al., 2020).	PartlyCarbon blocks removed roughly 60-70% of long-chain and about 40% of short-chain PFAS in that same study, with wide unit-to-unit spread. For a real detection, reverse osmosis at this same spot is the consistent answer.
Sediment and scale	PartlyA point-of-entry unit with a sediment pre-stage catches grit across every tap and protects appliances. It does not soften: scale is dissolved calcium and magnesium, which carbon leaves in the water, so hard-water scale needs a softener.	NoTreats one fixture, so it does nothing for the sediment or scale reaching the water heater, laundry, or any other tap in the house.
Drinking-water removal (lead, PFAS, dissolved contaminants)	PartlyIt improves the water at every tap but is not drinking-grade removal. Lead is added downstream of it, its PFAS performance is unreliable, and dissolved ions like nitrate or chromium-6 pass straight through carbon.	YesWhere removal for what you drink and cook actually happens. A certified carbon block covers the chlorine family and lead; reverse osmosis at the same spot adds the dissolved range carbon cannot hold.

Pick Whole-house carbon when

The shower and bath are the exposure you care about: chlorine and its volatile byproducts go airborne in hot water, and no kitchen filter reaches them.
Your water test has ruled out PFAS. Running point-of-entry carbon on a PFAS home risks releasing what the bed captures.
You want sediment and chlorine handled at every tap and appliance, not just the one you drink from.

Pick Under-sink carbon when

Lead is the concern. It enters at your own fixtures, downstream of any whole-house unit, so the fix has to sit at the tap you drink from.
You want drinking-grade removal for PFAS or dissolved contaminants. That is a point-of-use job, and for PFAS or a dissolved ion like nitrate or chromium-6, reverse osmosis is the reliable tool, not carbon.
You want the lowest-cost option that covers what you actually drink and cook with.

Common questions

Whole-house water filter vs under-sink: which do I need?

It depends on the exposure, and often you want both. A whole-house filter is the only one that reaches your shower and bath, where chlorination byproducts go airborne. An under-sink filter is where you get removal for what you drink and cook, and it is the only place that catches lead, since lead comes from your own fixtures downstream of a whole-house unit. Start with a water test, then match each filter to the problem it actually solves.

What is the difference between point-of-entry and point-of-use water filters?

Point-of-entry means the filter sits where the main line enters your home, so it treats every tap, shower, and appliance. Point-of-use means it treats a single fixture, almost always the kitchen tap, right before you drink. Point-of-entry gives coverage, including the shower route no kitchen filter reaches. Point-of-use gives drinking-grade removal at the one tap that matters most for what you ingest.

Does a whole-house filter remove lead?

No. Lead in tap water almost always comes from your home's own brass fixtures and pre-1986 solder, which sit downstream of where a whole-house unit lives. The water picks up that lead after it has already passed the filter. Lead is a point-of-use job: a filter certified to NSF/ANSI 53 for lead at the tap you drink from.

Can a whole-house filter handle PFAS?

Not reliably, and it can backfire. In a 73-home field study, whole-house carbon systems were widely variable, and some raised PFAS in the treated water once the carbon bed saturated and released what it had held (Herkert et al., 2020). If a test shows PFAS, the answer is reverse osmosis at the kitchen tap, not a tank at the entry.

If I can only install one, which should it be?

For most homes on chlorinated municipal water, start at the point of use: a certified filter at the kitchen tap covers the water you drink and cook, and it is the only fix for lead. Add whole-house carbon when the shower and bath route matters to you and a test has ruled out PFAS. The two are complements, not substitutes.