The Complete Home Water Filter Guide: Which Filter Actually Removes What (2026)

If you've looked up your water quality report and found contaminants — or you just want cleaner-tasting tap water — buying a filter is the obvious next step. But the sheer number of options is overwhelming: pitcher filters, faucet mounts, under-sink systems, whole-house units, reverse osmosis, UV purifiers. Which one do you actually need?

This guide cuts through the marketing and explains, based on EPA data and NSF certification standards, exactly what each filter type removes, what it doesn't, and how to match the right filter to the specific contaminants in your water.

The short answer: what filter do I need?

If you don't want to read the whole guide, here's the quick version:

Now let's look at each filter type in detail.

Activated carbon filters

Activated carbon is the most common filter technology. It's what you'll find inside Brita pitchers, PUR faucet mounts, and most refrigerator filters. Carbon works through adsorption — contaminants stick to the surface of the carbon as water passes through.

What activated carbon removes

Carbon filters are effective at removing chlorine and chloramine (which cause the "pool water" taste), volatile organic compounds (VOCs) like benzene and toluene, some pesticides and herbicides, trihalomethanes (TTHMs) and haloacetic acids (HAA5) — the disinfection byproducts that form when chlorine reacts with organic matter, and sediment and particulates that cause cloudy water.

What activated carbon does NOT remove

Standard carbon filters are not effective against dissolved minerals and salts, nitrates and nitrites, fluoride, arsenic, most heavy metals (without specific certification), bacteria and viruses, and most PFAS compounds (unless specifically certified to NSF P473).

Granular vs. carbon block

There's an important distinction within carbon filters. Granular activated carbon (GAC) — found in most pitchers — has loose carbon granules. Water can channel around the granules, making it less effective. Carbon block filters compress the carbon into a solid block, forcing all water through the carbon. Carbon block filters are significantly more effective and are what you'll find in higher-end faucet mounts and under-sink systems.

Key certifications for carbon filters

Look for NSF/ANSI 42 certification for chlorine taste and odor reduction. If you need lead removal, you must find a filter certified to NSF/ANSI 53, which tests for specific health-related contaminants. Not all carbon filters meet Standard 53 — a basic Brita pitcher, for example, is only certified to Standard 42.

Cost and maintenance

Pitcher filters cost $25–40 upfront with $5–8 replacement filters every 2 months. Faucet mounts run $25–35 with $10–15 replacement filters every 3 months. Under-sink carbon block systems cost $50–150 with $20–40 annual filter replacements. Most carbon filters need replacing every 2–6 months depending on usage and water quality.

Reverse osmosis (RO) systems

Reverse osmosis is the gold standard for home water purification. It forces water through a semipermeable membrane with pores so small that virtually nothing except water molecules can pass through.

What reverse osmosis removes

RO systems remove effectively everything: lead, copper, and other heavy metals, PFAS / forever chemicals, nitrates and nitrites, arsenic, fluoride, dissolved salts and minerals, bacteria and viruses, radionuclides like radium and uranium, and virtually all organic and inorganic contaminants. A good RO system removes 95–99% of total dissolved solids (TDS).

What reverse osmosis does NOT do well

RO membranes can be damaged by chlorine, which is why most systems include a carbon pre-filter. They also waste water — typically 2–4 gallons of water are flushed for every gallon produced, though newer systems are getting more efficient. RO removes beneficial minerals along with contaminants, though this is not a health concern for most people since we get most minerals from food. Some people notice the water tastes "flat" — a remineralization filter can fix this.

Types of RO systems

Under-sink RO systems are the most popular for homes. They connect to your cold water line, filter the water through 4–6 stages, and dispense through a dedicated faucet. Countertop RO systems require no installation — you fill a tank and it filters into a reservoir. These are great for renters. Whole-house RO systems exist but are expensive ($1,500+) and usually overkill for municipal water.

Cost and maintenance

Under-sink systems cost $150–300 upfront. Pre-filters (sediment and carbon) need replacing every 6–12 months ($15–30 each). The RO membrane itself lasts 2–3 years ($30–60 to replace). Total annual maintenance cost is typically $50–100. Countertop units run $200–400 with similar filter costs.

NSF 53 and NSF 58 certified filters

NSF certifications are the most reliable way to verify a filter's claims. The two most important standards for health protection are NSF/ANSI Standard 53 for carbon and adsorption filters, and NSF/ANSI Standard 58 for reverse osmosis systems.

What NSF 53 means

Standard 53 tests filters for removal of specific health-related contaminants. A filter can be certified to Standard 53 for some contaminants but not others — always check what specific contaminants are listed on the certification. Common Standard 53 certifications include lead reduction, cyst reduction (Cryptosporidium and Giardia), VOC reduction, and MTBE reduction.

What NSF P473 means

This is the newer protocol specifically for PFAS removal, covering PFOA and PFOS. If PFAS is your concern, look for NSF P473 certification specifically. Brands like Clearly Filtered, Berkey (with fluoride filters), and many RO systems have this certification.

How to verify certifications

Don't trust marketing claims. Verify certifications at NSF International's website (nsf.org) or the Water Quality Association's directory. Legitimate certifications will list the specific standard number and contaminants tested.

UV purification

Ultraviolet (UV) purifiers use UV-C light to kill or inactivate bacteria, viruses, and other microorganisms by disrupting their DNA. They're used as a final treatment stage, often after a carbon or sediment filter.

What UV removes

UV purification is effective against bacteria (E. coli, coliform, Salmonella), viruses (Hepatitis A, norovirus, rotavirus), and protozoa like Giardia and Cryptosporidium (at sufficient dosage). UV does NOT remove any chemical contaminants, heavy metals, minerals, or sediment. It purely addresses biological threats.

When you need UV

UV purification is most important for well water users, since municipal water is already disinfected. It's also worth considering if your water system has had coliform bacteria violations, or if you're in a rural area with aging infrastructure. For most people on treated municipal water, UV is unnecessary.

Cost and maintenance

Point-of-use UV systems cost $100–300. The UV lamp needs replacing annually ($30–60). Some systems include a pre-filter that also needs periodic replacement. Whole-house UV systems cost $300–700.

Distillation

Water distillers heat water to boiling, capture the steam, and condense it back into liquid water — leaving contaminants behind. It's one of the oldest and most effective purification methods.

What distillation removes

Distillation removes heavy metals (lead, mercury, arsenic), nitrates, dissolved solids, bacteria and viruses, fluoride, and most inorganic contaminants. It does NOT effectively remove VOCs and some pesticides that have boiling points lower than water — these evaporate and re-condense along with the water. A carbon post-filter solves this.

Drawbacks

Distillers are slow (4–6 hours per gallon), use significant electricity, and produce water that tastes flat. They're also not practical for large volumes. Most people who want comprehensive filtration are better served by reverse osmosis, which achieves similar results much faster.

Whole-house filtration

Whole-house (point-of-entry) systems filter all water entering your home, including water for showers, laundry, and dishwashing. They typically consist of a sediment pre-filter followed by a large activated carbon tank.

When whole-house filtration makes sense

Consider a whole-house system if your water has high sediment (discolored or cloudy water), you want chlorine removed from shower and bath water (chlorine can irritate skin and is inhaled as steam), you have well water that needs treatment before any use, or you want a baseline level of filtration for all water with a point-of-use system for drinking water.

Cost and maintenance

Basic whole-house carbon systems cost $300–800 installed. Sediment pre-filters need replacing every 3–6 months ($10–20). Carbon tanks last 3–5 years or 100,000–300,000 gallons before the carbon needs replacing ($100–200). More advanced systems with multiple stages can run $1,000–3,000.

Water softeners

Water softeners use ion exchange to remove calcium and magnesium — the minerals that cause hard water. They're technically conditioners, not filters, since they don't remove contaminants.

What water softeners do

Softeners eliminate scale buildup in pipes, water heaters, and appliances. They also prevent soap scum, improve lathering, and extend appliance life. Hard water above 7 grains per gallon (gpg) or 120 mg/L causes significant scaling.

What water softeners do NOT do

Softeners do not remove lead, PFAS, chlorine, bacteria, nitrates, or any other health-related contaminant. They add a small amount of sodium to the water. If you need both softening and contaminant removal, you'll need separate systems.

The full filter comparison chart

✓ Effective ~ Partial ✗ Not effective *Requires NSF 53 certification **Only if NSF P473 certified

How to choose: a step-by-step process

Step 1: Check your water quality. Use the ClearWater search tool to look up your water system by ZIP code. Note any violations, PFAS detections, and lead testing results. This tells you what you actually need to filter.

Step 2: Identify your contaminants of concern. Are they chemical (lead, PFAS, nitrates) or biological (bacteria, parasites)? Chemical contaminants require physical filtration; biological contaminants can also be addressed with UV.

Step 3: Match the filter to the contaminant. Use the chart above to find which filter types address your specific concerns. If you have multiple contaminants, choose the filter type that covers all of them — usually reverse osmosis.

Step 4: Verify the certification. Don't buy a filter based on marketing claims alone. Check for NSF/ANSI certification to the relevant standard (42, 53, 58, or P473). Verify at nsf.org or the WQA website.

Step 5: Consider ongoing costs. The purchase price is just the beginning. Factor in replacement filters, potential water waste (for RO), and electricity (for UV and distillers). A $150 RO system with $75/year in filter costs beats a $40 pitcher with $50/year in cartridges within 3 years — and removes far more contaminants.

Common filter myths

"All filters remove lead." False. Most basic carbon pitcher filters are NOT certified for lead removal. You need NSF 53 certification specifically for lead. Check the packaging — "reduces chlorine taste" is not the same as "reduces lead."

"Brita removes everything." False. Standard Brita pitchers are only certified to NSF 42 (chlorine taste and odor). They do not remove lead, PFAS, nitrates, bacteria, or most other health-concerning contaminants. Brita does make some models certified to NSF 53 for lead — but you need to buy the specific "Longlast+" filter, not the standard one.

"Bottled water is safer than filtered tap water." Not necessarily. Bottled water is regulated by the FDA with standards that are generally similar to EPA's tap water standards. Some bottled water IS tap water, just filtered. A good home filter gives you the same or better quality at a fraction of the cost and environmental impact.

"RO water is unhealthy because it removes minerals." This is largely a myth. The amount of minerals in drinking water is small compared to what you get from food. The World Health Organization has noted that RO water may contribute to slightly lower mineral intake, but for people eating a normal diet, this is not a health concern.

"Boiling makes water safe." Only partially true. Boiling kills bacteria and viruses effectively, but it does NOT remove chemical contaminants like lead, PFAS, nitrates, or pesticides. In fact, boiling can concentrate these chemicals as water evaporates. Only use boiling for biological contamination (e.g., boil water advisories).

What about well water?

If you're on a private well rather than a municipal water system, your water is not monitored by the EPA or your state. This means you're responsible for testing and treating your own water. At minimum, you should test annually for bacteria (total coliform and E. coli), nitrates, pH, and total dissolved solids. Consider testing for arsenic, radon, and any contaminants common in your area's geology.

For well water, a recommended setup is a sediment pre-filter followed by an activated carbon filter and a UV purifier for bacterial protection. If testing reveals specific contaminants like arsenic or nitrates, add reverse osmosis for drinking water.

Maintenance matters more than the filter you buy

The most expensive filter in the world won't protect you if you don't replace the cartridges on schedule. An expired carbon filter can actually release accumulated contaminants back into your water. Set reminders for filter changes and follow the manufacturer's replacement schedule — or sooner if you notice reduced flow rate or changes in taste.

Check your water first. Search your ZIP code on ClearWater to see your water system's violations, PFAS data, and lead testing results — then come back here to find the right filter.