Pick a water filter type by answering two questions in order: what’s in your water that you want reduced, and which taps need treated water. For drinking and cooking water, a point-of-use filter (a pitcher, faucet-mounted, countertop, refrigerator or under-sink unit) is the type the EPA calls best suited. A whole-house, or point-of-entry, system treats every tap, and the EPA says it’s best suited to a water source with consistent and significant contamination. Reverse osmosis (RO) is a treatment process, not a location, and most home RO systems sit under the kitchen sink.
The type alone doesn’t tell you what a filter removes. The EPA says no single treatment system removes all contaminants, and the Minnesota Department of Health says the same about single treatment units. What a specific filter reduces is in its certification listing.
Water filter types at a glance
| Type | What it treats | How it’s set up | Standards to look for |
|---|---|---|---|
| Pitcher | Water you pour into it | Filled by hand | NSF/ANSI 42, 53 (lead, PFAS claims), 401 |
| Faucet-mounted | One existing kitchen faucet | Attaches to the faucet, switches on and off | NSF/ANSI 42, 53 |
| Countertop | Water at one spot | Supply-line hookup or filled by hand | NSF/ANSI 42, 53 |
| Refrigerator | Fridge water and ice | Built-in cartridge feeds the dispenser | NSF/ANSI 42, 53 |
| Under-sink filter | One tap, often a dedicated faucet | Plumbed to the water supply line | NSF/ANSI 42, 53, 401 |
| Under-sink RO | One dedicated faucet | Membrane plus a drain line for reject water | NSF/ANSI 58, plus 42 or 53 for added stages |
| Whole-house | Every tap and appliance | Installed where water enters the home | Depends on the media; check the listing |
| Shower | One shower | Inline filter or filtered head | NSF/ANSI 177 |
Setup descriptions follow the EPA WaterSense guide. Standards follow the EPA’s technology table and lead and PFAS guidance, and NSF’s NSF/ANSI 177 listing. A standard number is not a claim: check which contaminants the exact model is certified for.
Point-of-use filters: drinking and cooking water
The EPA says point-of-use devices are best suited for treating water used for drinking and cooking, and its guide advises against oversizing, noting that many uses, such as flushing toilets and washing clothes, don’t need extra treatment.
Pitcher filters
The EPA notes that pitcher filters depend on you to fill them by hand. Certified models vary widely in what they reduce, from chlorine taste to lead and PFAS, so compare listings rather than formats. Our best water filter pitchers list compares certified models by their listed claims.
Faucet-mounted and faucet-integrated filters
Faucet-mounted filters attach to an existing faucet and can be switched between filtered and unfiltered water, the EPA says. A faucet-integrated filter is a faucet with the filter housing built in rather than a separate filter fitted to the tap. Faucet filters are also covered by the EPA lead tool.
Countertop systems
Countertop or stand-alone systems can sit away from the sink, the EPA says, and either draw from the water supply line or are filled by hand as a self-contained unit.
Refrigerator filters
Refrigerator filters are built into many modern refrigerators and supply water and ice through a dispenser. The EPA says to replace them based on the manufacturer’s instructions, and its lead tool covers refrigerator filters as well. To compare OEM and generic replacement cartridges, see our refrigerator filter replacement guide . If you’re weighing a fridge filter against treating the whole home, see whole-home vs refrigerator water filter .
Under-sink filters
Under-sink systems are typically installed under the kitchen sink and send treated water to a dedicated faucet, according to the EPA, which adds that they can treat larger quantities of water. Compare certified models in our best under-sink water filters .
Reverse osmosis systems
RO uses pressure to force water through a semi-permeable membrane, which produces a stream of treated water and a stream of reject water. The EPA says point-of-use RO systems can potentially remove contaminants such as lead, volatile organic compounds, PFAS, arsenic, bacteria and viruses. The standard for RO systems is NSF/ANSI 58, and the EPA notes that an RO system with added filter or UV stages could also be certified to NSF/ANSI 42, 53 or 55.
The trade-offs are water use and minerals. The EPA says a typical point-of-use RO system sends five gallons or more of reject water down the drain for every gallon of treated water, while WaterSense labeled models must send 2.3 gallons or less. Its technology table also lists the removal of beneficial minerals such as calcium as a limitation. EPA WaterSense says it doesn’t intend to promote RO for all applications, and that filtration alone is sometimes enough. See our best reverse osmosis systems , and for the RO-or-whole-house question, our RO vs whole-house filtration guide .
Whole-house (point-of-entry) systems
A point-of-entry system is installed where water enters the building and treats water for every use, including toilet flushing, showering and laundry. The EPA says these systems are best suited where the water source poses consistent and significant contamination challenges, and that they may require plumbing changes and professional maintenance. The Minnesota Department of Health describes the split the same way: point-of-use units treat water at one faucet or location, and point-of-entry units treat all of the water in your home.
What a whole-house system reduces depends on the media inside it, so check the listing for each stage. Our best whole-house water filters list compares current systems. For well owners deciding between a whole-house unit and a kitchen filter, see well water: whole-house vs point-of-use .
Softeners aren’t filters. Hardness rises with calcium and magnesium levels. The EPA says some hardness is generally not a health hazard, and points to NSF/ANSI 44 for water softeners or IAPMO/ANSI Z601 for scale reduction devices.
Shower filters
Shower filters fit inline or come as a filtered showerhead. Their standard is NSF/ANSI 177, which NSF titles “Shower Filtration Systems - Aesthetic Effects.” Our best shower filters list covers models with an NSF/ANSI 177 listing.
Match the type to what’s in your water
- Chlorine taste or odor: the EPA points to NSF/ANSI 42, the standard for products that improve taste and odor. The EPA also notes that water left in an open pitcher in the refrigerator for a day or two loses chlorine taste and odor as the chlorine evaporates.
- Lead: the EPA says to look for NSF/ANSI 53 with a lead reduction claim, and also NSF/ANSI 42 for Class I particulate reduction. Its lead tool covers faucet, refrigerator and pitcher filters and says lead claims of 5 parts per billion or less can be found on the performance data sheet or in the certifier’s listing.
- PFAS: the EPA says to check for an NSF/ANSI 53 or NSF/ANSI 58 PFAS claim. It lists activated carbon, RO and ion exchange resins as filter types that can be effective, and notes that, as of April 2024, certifications focused on PFOA and PFOS.
- Nitrate or bacteria: the EPA’s technology table says filtration doesn’t remove nitrates, bacteria or dissolved minerals. It says some RO systems can reduce nitrates, and that UV systems (NSF/ANSI 55) inactivate bacteria, viruses and protozoa but aren’t effective against chemicals.
- Hardness and scale: that’s a softener or scale-reduction job (NSF/ANSI 44 or IAPMO/ANSI Z601), not a filter.
How to choose a water filter type
- Find out what’s in your water first. If you’re on public water, your utility should send a consumer confidence report each summer, the EPA says. If you’re on a well, the EPA says to have it tested periodically by a state-certified lab.
- Name the goal. Taste, lead, PFAS and hardness each point to a different standard and often a different type.
- Decide where you need it. For drinking and cooking only, the EPA points to point-of-use treatment. Treat every tap only when the source itself needs it.
- Check the listing for the exact model. The Minnesota Department of Health says to choose a unit certified by NSF, UL or WQA for your contaminant where a certification exists, and that these bodies don’t certify units for every contaminant. Our certification guide shows how to read a listing.
- Plan for maintenance. The EPA says filters should be replaced on the maker’s schedule and that unmaintained systems may make water quality worse. The Minnesota Department of Health advises testing the treated water after installation.
Sources
- EPA WaterSense Guide to Selecting Water Treatment Systems (point-of-use and point-of-entry types, technology standards and limitations, softener standards, chlorine, CCRs, well testing, maintenance)
- EPA WaterSense: Point-of-Use Reverse Osmosis Systems (how RO works, contaminants, reject water, WaterSense criterion, not for all applications)
- EPA consumer tool for filters certified to reduce lead (NSF/ANSI 53 lead claim, NSF/ANSI 42 Class I, filter types covered)
- EPA: Reducing PFAS in Your Drinking Water with a Home Filter (NSF/ANSI 53 and 58 PFAS claims, filter technologies, PFOA and PFOS)
- Minnesota Department of Health: Home Water Treatment Facts (point-of-use and point-of-entry definitions, certifiers, no single unit removes all contaminants, testing after installation)
- NSF/ANSI 177 listings at NSF (standard title for shower filtration systems)
Sources were checked on October 9, 2026. This is desk research from government and certifier sources; Better Water Guide has not tested any of these filter types, and this guide isn’t a water-safety diagnosis.