A Faucet Water Filter Removes What Its Label Certifies

Yes, a faucet water filter works, within the limits of its certification. It clips onto the tap and treats water as you draw it, and the standard named on its packaging tells you what it reduces. At The Indoor Report, our rule is to point readers to a certification listing rather than a model number, because the listing is the part of the claim you can verify.

Most faucet filters lean on activated carbon. Activated carbon mainly reduces chlorine, taste, odor and some organic chemicals and does little to dissolved minerals such as calcium.

Lead needs its own check. The EPA lead action level is 15 parts per billion, and a filter should be certified for lead reduction under the relevant standard before you rely on it for lead.

A Faucet Water Filter Removes Only What Its Certification Lists

A faucet water filter removes the contaminants its certification lists, and you should assume nothing beyond that list. The Centers for Disease Control and Prevention (CDC) says different home water filters remove different things, and it advises reading the label for what a filter is certified to remove. Two faucet filters can carry different listings.

The standards come from NSF International. They appear as NSF/ANSI plus a number. Three numbers come up on home drinking water filters.

Before you buy for a health reason such as lead, look up the exact product listing at nsf.org, which is the step NSF International advises. A taste claim and a health claim sit under different standard numbers, so read the number as well as the wording.

A Faucet Mount Treats Water at the Spout With a Bypass Switch

A faucet mount attaches to the end of the spout, so each glass you fill passes through the cartridge at the moment you draw it. A typical unit has a switch that sends water through the filter or around it.

The bypass setting is for jobs that do not need filtered water, such as washing dishes.

Hot water is generally not meant to run through a faucet-mounted filter. The maker's manual sets the water temperature limit for each unit. Follow that limit.

The carbon inside reduces chlorine taste and odor, so a carbon faucet filter fits a complaint about chlorine in tap water. For how carbon media works, read our activated carbon water filter guide.

Spout Shape Decides Whether a Faucet Water Filter Fits

A faucet water filter fits only a spout that accepts its adapter, and some spouts do not. Spouts that pull out, spray, or have an unusual shape may not accept a standard faucet adapter.

The maker's compatibility list for that unit settles the fit. If your spout type is missing from that list, treat the filter as incompatible. Ask three questions about the tap before you buy.

1. Does the spout pull out on a hose? If yes, the maker's compatibility list has to name that spout style.
2. Does the head spray or switch between spray patterns? Spray heads are among the spouts that may not take a standard adapter.
3. Is the spout shaped differently from a plain round tip? An unusual shape may not accept a standard faucet adapter.

Cartridge Life Follows the Maker's Schedule

Replace a faucet filter cartridge on the schedule its maker prints, because the CDC says filters need maintenance and replacement per the maker's directions. The CDC also warns that an unmaintained filter can stop working or become a place where microbes grow.

A wet cartridge left in place past its date is the risk to plan around. The CDC points to the maker for the interval, so the cartridge box or manual is the source for your replacement date. Four habits keep the cartridge on schedule.

1. Write the install date on the cartridge box or a calendar on the day you fit it.
2. Use the bypass setting for dishes and other water you will not drink, which extends cartridge life.
3. Check the maker's manual on water temperature before running hot water.
4. Replace the cartridge on the maker's date, even if the water still tastes fine.

Lead and Microbial Contamination Need a Specific Certification

A faucet filter handles lead or microbes only when its listing says so. A filter should be certified for lead reduction under the relevant standard before you rely on it for lead. According to NSF International, NSF/ANSI 53 is the standard that covers health effects such as lead.

Microbial contamination is a separate question. According to the CDC, a filter does not make microbiologically contaminated water safe unless it is specifically certified for that purpose. EPA and CDC treat boil-water advisories separately.

If you have a lead result or a utility notice in hand, start with our pages on lead in water and whether tap water is safe to drink.

Faucet, Pitcher, Under-Sink and Countertop Filters Compared

Every filter format, faucet mount included, is judged by its certification listing. Each format follows its own maker's schedule.

The faucet mount depends on spout shape.

Each format has its own guide: water filter pitchers, under-sink water filters, and countertop water filters. For a rental kitchen, our apartment water filter guide covers the same choice.

Choosing a Faucet Water Filter Starts With Your Contaminant and Spout

Pick a faucet water filter when your spout is on the maker's compatibility list and your goal matches its certification. A filter certified to NSF/ANSI 42 fits a complaint about chlorine taste or odor. A filter listed for lead under NSF/ANSI 53 is the one to consider when lead is the concern.

This advice does not serve four groups of readers.

• Homes under a boil-water advisory or with known microbial contamination, unless the filter is specifically certified for that purpose.
• Kitchens with a pull-out, spray or unusually shaped spout that the maker does not list.
• Anyone whose main complaint is calcium or other dissolved minerals, which activated carbon does little to reduce.
• Anyone who wants a reverse osmosis system, which NSF/ANSI 58 covers as a separate system type.