Choosing from the best home water filters starts with what your water needs, then with what your home lets you install. Pick the type here, then open its guide for the exact model.
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First know your water. City water comes with a yearly report from the supplier (EPA); a private well needs its own test (EPA). Then buy a model whose certification listing names what you want reduced (CDC).
Start with what your water needs. The type comes last.
A guide helps you choose. Main-line work and permit questions belong with a licensed plumber.
Six filter types, from no install to the main water line. Each one opens the PlumbingPicks guide that lists its exact picks.
Disclaimer: Illustration for visual purposes
No install
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On the faucet spout
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Plugs in on the counter
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In the sink cabinet
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Cabinet, drain and its own faucet
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On the main water line
On a private well and want every tap filtered? Start with the well-water guide. Comparing two owner types? See under-sink vs whole-house.
This Old House plumbing expert Richard Trethewey walks through pitcher, faucet-mounted, under-sink, reverse osmosis and whole-house filters.
Where the water comes out, whether a renter can use it, and what your home needs. No prices, stars or lab scores.
| Type | Filtered water comes out | Renters | What your home needs |
|---|---|---|---|
| Pitcher | From the pitcher. You refill it by hand. | Yes | Nothing. Fill it at the tap. |
| Faucet mount | From your kitchen faucet. | Yes It screws on where the faucet’s aerator was (PUR). | A standard faucet. PUR says pull-out and handheld faucets don’t fit its systems (PUR). |
| Countertop RO | From the unit on the counter. Plug-in units such as AquaTru’s are filled by hand (AquaTru). | Yes Plug-in units such as AquaTru’s need no plumbing or water line (AquaTru). | For a plug-in unit, an outlet and counter space. |
| Under-sink filter | From your current faucet, or from its own faucet, depending on the model (Waterdrop). | Owner’s OK It changes the owner’s plumbing. | The cold-water line in the sink cabinet, room for the filter, and a faucet hole if the model adds its own faucet (Waterdrop). |
| Under-sink RO | From its own faucet (iSpring). | Owner’s OK It changes the owner’s plumbing. | The cold-water line, a sink-drain connection, a faucet hole, and room for the tank on tank models (iSpring). |
| Whole house | From every tap. It treats water as it comes into the house (CDC). | Owner’s OK It goes on the owner’s main line. | Work on the main water line. That belongs with a licensed plumber. |
Upkeep is the same job for every type: change the cartridges on the maker’s schedule (CDC). Under-sink RO has more of them: a membrane plus several cartridges (iSpring).
For under-sink filters and under-sink RO, check four things before you buy. A flashlight and a tape measure will do.
Under-sink RO kits can come with their own faucet and expect a hole in the counter or sink; iSpring’s kit does (iSpring). Some under-sink filters add a faucet too; others feed your current one (Waterdrop). Can’t drill? A faucet mount, a plug-in countertop RO unit or an under-sink filter that feeds your current faucet skips this step.
Under-sink filters connect to the cold supply under the sink (Waterdrop). Make sure that valve turns and closes all the way. Fix a stuck or leaking valve first.
Measure the clear width, height and depth beside the drain trap. Compare it with the system’s size on its guide, and leave room to change cartridges.
Under-sink RO also connects to the sink drain; iSpring’s kit uses a drain saddle. Tank models also need floor space for the tank (iSpring). Countertop RO skips this.
Renting? Anything under the sink changes the owner’s plumbing. Get a written OK first, or start with a pitcher, a faucet mount or a plug-in countertop RO unit.
What a filter removes. That depends on the exact model and its certification listing (NSF). Filters cannot remove some types of harmful substances (CDC).
Compare what two filters cost to own, not just to buy. Type in today’s prices from the product pages and the maker’s cartridge life. This page shows no prices.
3-year cost = unit price + (cartridge price × replacements per year × 3)
There is no single best water filtration system for home use. The best one matches your need and passes these checks in your home.
Some filters make water taste better, others remove harmful chemicals, and others remove certain germs (CDC). Know which one you want.
Point-of-use filters serve a single tap, such as the kitchen sink. Whole-home filters treat water as it comes into the house (CDC).
Renters: a pitcher, a faucet mount or a plug-in countertop RO unit. Owners can use any type. Main-line work belongs with a licensed plumber.
Look it up in the certifier’s listing, such as NSF’s database (NSF). That check lives on each type’s guide, and on the NSF-certified filter guide. For lead at the drinking tap, see the lead-filter guide.
Yes. A pitcher, a faucet mount and a plug-in countertop RO unit leave the plumbing alone. A faucet mount screws on where the faucet’s aerator was (PUR). Plug-in countertop RO units such as AquaTru’s need no plumbing or water line (AquaTru).
Limit: under-sink and whole-house filters change the owner’s plumbing. Get a written OK first.
If you mostly care about the water you drink and cook with, start with a drinking-water filter at one tap. A whole-house filter is a home water filtration system that treats water as it comes into the house, so every tap gets it (CDC).
Limit: which one you need depends on what you want reduced. The exact model’s certification listing shows that.
No. An under-sink RO system connects to the cold-water line and the sink drain and has its own faucet. iSpring’s under-sink kit, for example, includes a drain saddle, a faucet and a storage tank (iSpring). A plug-in countertop RO unit such as AquaTru’s plugs into an outlet and is filled by hand, with no plumbing or water line (AquaTru).
Limit: install needs vary by model. Check the maker’s manual for the exact system.
With a water test. Private well owners are responsible for their own drinking water (EPA). EPA suggests testing every year for total coliform bacteria, nitrates, total dissolved solids and pH (EPA). Then, for every tap, use the well-water guide. For one tap, the one-tap types above still apply.
Look up the exact model in the certifier’s own listing. CDC suggests checking the label for an NSF certification, then looking up the product in NSF’s database to see what it is certified to remove (CDC, NSF).
Isaac Daniels
Licensed Journeyman Plumber
Research-led. Filter types are sorted by the finder’s questions: what you want the filter to fix, where your water comes from, one tap or every tap, and rent or own. Then by install and upkeep, from the maker documents in Sources.
Isaac has tested the listed filter products and has more than 6 years of experience.
It doesn’t pick a second winner for a job another PlumbingPicks guide already covers.
Links checked October 30, 2026. Source text last read October 29, 2026.
Each one is also linked next to the claim it supports.