Home water filters, explained

A filter can genuinely improve your water, but only if it’s matched to the contaminant you actually have. Here are the main types of home filtration, what each one removes, what it doesn’t, and how to choose. Grounded in guidance from the CDC, EPA, and NSF.

Start with what’s in your water

There is no single “best” filter; the right choice depends on what you’re trying to remove. Work through these four steps before you buy.

1

Find out what’s in your water

If you’re on public water, read your utility’s annual Consumer Confidence Report (also called a water quality report). On a private well, or to confirm, use a certified lab test. This tells you which contaminants, if any, to target.
2

Match the filter to the contaminant

No technology removes everything. Use the comparison table below to see which filter types actually address your specific concern: lead, PFAS, nitrate, taste, and so on.
3

Look for the certification

Manufacturer claims are only meaningful when a third party has verified them. Look for an NSF/ANSI certification (from NSF, WQA, or IAPMO) for the specific contaminant you care about; see the guide further down.
4

Maintain it

Every filter loses effectiveness as it clogs or saturates. Replace cartridges and membranes on the manufacturer’s schedule. A neglected filter can be worse than none.

The main types of home filters

Most household setups use one of these six approaches, sometimes several in series (for example, sediment → carbon → RO).

Activated carbon

Most common

Pitchers · faucet-mount · refrigerator · countertop · under-sink

Removes: Chlorine, bad taste and odor, many VOCs and disinfection by-products. Certified carbon-block versions also reduce lead, mercury, some pesticides, and certain PFAS.
Limits: Does not remove dissolved minerals, nitrate, or arsenic, and does not reliably remove bacteria or viruses. Effectiveness fades as the cartridge saturates, so replace it on schedule.

Look for NSF/ANSI 42 & 53

Reverse osmosis (RO)

Under-sink · countertop

Removes: The widest reach of any home system: lead, arsenic, fluoride, nitrate, chromium, PFAS, dissolved solids, and many other inorganic and synthetic contaminants.
Limits: Sends several cups of water down the drain per cup filtered, strips out beneficial minerals, works slowly through a storage tank, and costs more up front.

Look for NSF/ANSI 58

Ion exchange & softeners

Whole-house (softeners) · under-sink (anion units)

Removes: Softeners swap out the calcium and magnesium that cause hard-water scale. Specialized anion-exchange resins can also reduce nitrate, arsenic, and PFAS.
Limits: A standard softener is a scale-control device, not a purifier: it adds a little sodium and does not remove germs. Match the resin to the contaminant you care about.

Look for NSF/ANSI 44

Distillation

Countertop · plumbed units

Removes: Boils water and condenses the steam, leaving heavy metals, minerals, nitrate, and many chemicals behind. The heat also kills bacteria, viruses, and parasites.
Limits: Slow and energy-hungry, and it does not capture chemicals that boil off with the water (some VOCs). Best for small daily volumes.

Look for NSF/ANSI 62

UV (ultraviolet)

Under-sink · whole-house

Removes: Ultraviolet light inactivates bacteria, viruses, and parasites (the germs behind most boil advisories) without chemicals.
Limits: Does nothing for chemicals, metals, or sediment, and needs clear water plus continuous power. Almost always paired with a carbon or sediment pre-filter.

Look for NSF/ANSI 55

Sediment & ceramic

Whole-house pre-filter · countertop · gravity units

Removes: Physically strain out sand, rust, silt, and other particulates. Fine ceramic elements also capture bacteria and parasites (cysts).
Limits: Do not remove dissolved chemicals, metals, or viruses. Usually the first stage ahead of a carbon or RO system rather than a complete solution.

Look for NSF/ANSI 42 (mechanical)

One specialty worth knowing: for fluoride or arsenic specifically, activated alumina filters are a targeted, lower-cost option certified under NSF/ANSI 53, useful where reverse osmosis is overkill.

What each filter removes, at a glance

A quick cross-reference. Certified performance varies by product, so always confirm the certification for your specific contaminant.

Contaminant	Carbon	RO	Ion exch.	Distill	UV	Sediment
Chlorine, taste & odor	●	●	○	●	○	○
Lead	◐	●	◐	●	○	○
PFAS ("forever chemicals")	◐	●	◐	○	○	○
Arsenic	○	●	◐	●	○	○
Fluoride	○	●	◐	●	○	○
Nitrate	○	●	◐	●	○	○
Bacteria & viruses	○	●	○	●	●	○
Parasites (cysts)	◐	●	○	●	●	◐
Sediment & particulates	◐	●	○	●	○	●
Hardness / scale	○	●	●	●	○	○

● Removes ◐ Partial, or only when certified for it ○ Not designed to remove

Carbon Activated carbon RO Reverse osmosis Ion exch. Ion exchange & softeners Distill Distillation UV Ultraviolet Sediment Sediment & ceramic

Which clean-water setup is right for you?

Three common ways to get cleaner water at home, compared on the things families actually weigh.

What matters	Home filters	Bottled delivery	Air-to-water
What it removes	Varies by type; reverse osmosis covers the most	Depends on the brand and source	Broad: non-detect PFAS, lead and microplastics in third-party testing
Works during an advisory or outage	No; still tied to your tap, and most don’t remove germs	Only if it’s in stock; deliveries can lapse	Yes; it makes its own water, independent of the pipes
Effort to keep it going	Occasional filter changes	Recurring deliveries and heavy jugs to haul and store	Runs on its own, with a filter change occasionally
Plastic waste	Spent cartridges	A lot: bottles and jugs	Minimal; no bottles
Cost over time	Low to moderate	Recurring, and it adds up over the years	Higher up front, low per gallon after

Each has its place. The right choice depends on what you’re removing, how much effort you want, and whether you need water that keeps flowing when the tap can’t.

Air to water generation

A new countertop appliance makes clean drinking water from the air every day. No pipes, no advisories, no PFAS, no plastic bottles.

Non-detect for PFAS, microplastics and lead in third-party lab testing: the chemical contaminants that boiling can’t remove and basic pitchers often miss.
No plumbing, no bottles, no delivery. It runs on a standard outlet and needs only about 10% humidity in the room.
Makes roughly 0.75 to 2.5 gallons a day, refilling a fresh pitcher on its own.

Six stages of filtration + Hospital-grade air filter at intake

1Sediment pre-filterRemoves particulates
2Activated carbonPolishes taste & odor, adsorbs trace organics
3Electropositive captureGrabs the finest sub-micron particles
4Fine membraneA tight barrier for dissolved contaminants
5UV-C treatmentReduces biological activity
6RemineralizationAdds back calcium, magnesium & potassium

Learn more here

Reading the NSF/ANSI certification

New to filters? This is how you trust the label. An NSF/ANSI certification is an independent seal of approval: a filter earns one only after a third-party lab confirms it really removes what the box claims. Think of it as your shortcut past the marketing. The number just tells you what was actually tested:

Aesthetic effects. Taste, odor, chlorine, and particulates. Does not mean the water is safe from health contaminants.

Health effects. Lead, certain heavy metals, VOCs, parasitic cysts, and specific PFAS listings.

Reverse osmosis systems. Certifies a full RO system, with optional claims for arsenic, lead, PFAS, fluoride, and more.

Ultraviolet treatment. UV systems that inactivate bacteria, viruses, and cysts.

Distillation systems. Home distillers and the contaminants they reduce.

401

Emerging compounds. Trace pharmaceuticals, pesticides, and chemicals like BPA not yet federally regulated.

Certification is contaminant-specific: a filter can be “NSF 53 certified” for cysts but not for lead. Check the product’s official data sheet for the exact claims, and verify the mark in the certifier’s online database (NSF, WQA, or IAPMO).

Important: a filter is not a substitute for boiling

During a boil water advisory, most household filters (carbon pitchers, faucet-mount units, refrigerator filters) do not make the water safe. They are not designed to remove bacteria and viruses. Per the CDC, you should still boil your water or use bottled water even if it’s filtered.

The exception is a system specifically certified to remove microbes: for example UV (NSF/ANSI 55), reverse osmosis, or a purifier certified to NSF Protocol P231. When in doubt, boil.

See what to do during an advisory →

Sources

CDC: Choosing Home Water Filters Filter types, point-of-use vs point-of-entry, and why most filters don’t remove bacteria and viruses.
U.S. EPA: Overview of Drinking Water Treatment Technologies How activated carbon, reverse osmosis, ion exchange, and other technologies work.
U.S. EPA: Filters Certified to Reduce PFAS Activated carbon, reverse osmosis, and ion exchange as the PFAS-reduction technologies.
NSF: Water Treatment Device Standards What NSF/ANSI standards 42, 53, 55, 58, 62, and 401 each certify.

This page is general educational information, not a product endorsement or personalized advice. Confirm any filter’s certification for your specific contaminant, and follow your local water provider’s guidance during an active advisory.