10 Water Filter Cartridge Types, in the Order Water Meets Them

Nearly every home cartridge comes in 1 of 4 sizes: 10 or 20 inches long, 2.5 or 4.5 inches wide.

That size only decides whether it fits your housing. What’s packed inside decides what actually comes out of your water.

Below are the 10 water filter cartridge types you’ll run into, in the order water meets them, with what each one removes and misses.

How This List Is Ordered

The 10 water filter cartridge types below are listed in the order water passes through them in a home system. Sediment comes first, then carbon, then special media and the RO membrane.

That order matters because each stage of filtration protects the one after it.

Every cartridge also has a format (its size and housing) and a media (what’s inside). A “20-inch carbon block” names both in 3 words.

The 10 Water Filter Cartridge Types

The 10 main water filter cartridge types fall into 4 families: sediment (spun, string-wound, pleated), carbon (GAC, carbon block, catalytic), specialty media (KDF, ion exchange resin, activated alumina) and the RO membrane.

Each entry says what the cartridge removes, what it misses and who should skip it.

1. Spun Polypropylene Sediment Cartridges

A spun (melt-blown) polypropylene cartridge is the standard first stage in most home water filters.

It traps sand, silt and rust through its whole thickness, so finer media downstream doesn’t clog.

• Best for: city or well water with visible grit. Skip it if your water is already clear and you only want better taste.
• Removes: sand, silt, rust flakes and other suspended solids.
• Misses: chlorine, dissolved metals, minerals and bacteria.
• First step: Read the micron number on your old cartridge’s end cap.

Spun cartridges are depth filters: instead of one flat mesh, they trap dirt through their whole thickness. The outer layers are loose and the core is tight, so big particles stop early and small ones stop deeper in.

The catch is that you can’t wash one out. Once it’s full, it goes in the trash.

2. String-Wound Sediment Cartridges

A string-wound cartridge is polypropylene or cotton yarn wrapped tight around a core with holes in it.

Like a spun cartridge, it’s a depth filter, but it’s built to hold a heavier load of particulate matter.

• Best for: well water with a lot of sand or silt. Skip it if your sediment is light and fine.
• Removes: coarse and medium sediment, scale and rust.
• Misses: anything dissolved, including iron that hasn’t turned to rust yet.
• First step: Search your housing model plus “string wound” to confirm the fit.

Water flows from the outside in, and particles lock into the fiber matrix as they go. That makes string-wound cartridges a common pick for a sediment water filter on the main line.

In other words, choose string-wound when the problem is volume of grit, not tiny particles.

3. Pleated Sediment Cartridges

A pleated cartridge folds a flat sheet of polypropylene or cellulose into an accordion, which packs more surface area into the same housing.

It’s a surface filter, so particles stop on the outside instead of deep inside.

• Best for: water with a steady load of larger particles. Skip it if your sediment is mostly very fine silt.
• Removes: sand, dirt and rust.
• Misses: chlorine, odors and dissolved contaminants.
• First step: Check the box for “washable” or “reusable” before you plan to rinse it.

Some pleated cartridges can be hosed off and reused, so you buy fewer on gritty water.

4. Granular Activated Carbon (GAC) Cartridges

A GAC cartridge is a shell filled with loose granules of activated carbon, and it’s the go-to for fixing chlorine taste and smell.

Carbon filters work by adsorption: contaminants stick to the carbon’s huge internal surface as water passes through its pores.

• Best for: whole-house carbon stages where you need high flow. Skip it if you need lead or cyst reduction.
• Removes: chlorine, bad taste and odor, and many organic compounds.
• Misses: fine particles, most heavy metals, minerals and microorganisms.
• First step: Look on the label for whether it’s GAC or carbon block before you swap brands.

Loose granules let water through fast with little pressure drop. That’s why a chlorine water filter for the whole house often uses GAC.

The downside? Water can carve channels through a loose bed and skip some of the carbon.

5. Carbon Block Cartridges

A carbon block cartridge is activated carbon powder pressed into a solid, porous cylinder, so its filtration is far finer than loose GAC.

Water moves slower, but it touches more carbon on the way through.

• Best for: under-sink and countertop drinking water. Skip it if your housing feeds the whole house and pressure is already low.
• Removes: chlorine, bad taste, odor, many chemicals and fine particles.
• Misses: dissolved minerals, salts and most viruses.
• First step: Put a sediment cartridge in front of it if your water carries grit.

A carbon block also strains water like a screen, so it catches lead, cysts and fine particles that loose GAC lets pass, according to a Crystal Quest cartridge guide.

That double job is why carbon block is the most useful single cartridge for drinking water. Grades and sizes vary a lot between carbon block water filter models.

6. Catalytic Carbon Cartridges

A catalytic carbon cartridge is carbon treated to break down chloramine and the gas behind a rotten-egg smell (hydrogen sulfide). Plain carbon handles both poorly.

If your utility disinfects with chloramine, plain carbon won’t keep up.

• Best for: homes on chloramine-treated city water or wells with a rotten-egg smell. Skip it if your utility uses plain chlorine.
• Removes: chloramine, hydrogen sulfide odor and chlorine.
• Misses: sediment, hardness and dissolved metals.
• First step: Check your water utility’s yearly report for the word “chloramine”.

If your water smells like eggs, a sulfur water filter cartridge built on catalytic carbon goes after the odor at its source. If chloramine is the issue, a dedicated chloramine water filter gives the carbon enough contact time to work.

7. KDF (Redox) Cartridges

A KDF cartridge holds a copper-zinc alloy that cleans water through a chemical reaction (redox) instead of trapping or adsorbing contaminants.

Free chlorine turns into harmless chloride, and some dissolved metals bond to the media.

• Best for: shower filters and carbon systems that need extra chlorine and metal reduction. Skip it if you need chemical or VOC removal on its own.
• Removes: chlorine, some water-soluble heavy metals such as lead and mercury, and, in KDF-85 blends, iron and hydrogen sulfide.
• Misses: organic chemicals, fluoride and hardness minerals.
• First step: Check whether the cartridge says KDF-55 (chlorine and metals) or KDF-85 (iron and sulfur).

KDF usually rides alongside carbon in the same cartridge, and it slows bacteria and algae growth inside it.

8. Ion Exchange Resin Cartridges

An ion exchange cartridge holds resin beads that swap unwanted dissolved ions for harmless ones, which mechanical and carbon cartridges can’t do.

Different ion exchange resins target different ions.

• Best for: small-scale hard water, nitrate, sulfate or arsenic problems at one tap. Skip it if your whole house has hard water; a softener fits that job.
• Removes: hard water minerals, nitrate, sulfate, arsenic or some metals, based on the resin.
• Misses: sediment, chlorine taste and microorganisms.
• First step: Match the resin type to the one contaminant your water test flagged.

Unlike a softener, these cartridges don’t regenerate. When the resin runs out of exchange sites, you replace the whole cartridge.

So if hardness is your main complaint, compare a cartridge with a full ion exchange water filter system first.

9. Activated Alumina Cartridges

An activated alumina cartridge uses porous aluminum oxide beads to grab fluoride and arsenic. Carbon barely touches either one.

So it’s a specialty stage you add for a tested problem, not an everyday one.

• Best for: water with tested fluoride or arsenic levels you want lowered. Skip it if you just want better taste.
• Removes: fluoride, arsenic and some other dissolved ions.
• Misses: chlorine, sediment and bacteria.
• First step: Get a lab water test that reports fluoride and arsenic before you buy.

Activated alumina works best with slow flow and the right pH. That’s why it usually sits in a dedicated fluoride water filter rather than a fast whole-house line.

10. Reverse Osmosis Membranes

A reverse osmosis membrane is a replaceable cartridge that forces water through a semipermeable sheet, blocking most dissolved solids, salts and metals.

It’s the finest stage of filtration in home water filters, so it always sits behind sediment and carbon cartridges.

• Best for: drinking water with dissolved contaminants a carbon block can’t reach. Skip it if you only want better-tasting city water.
• Removes: dissolved solids, salts, fluoride, nitrate, heavy metals and most germs.
• Misses: little on its own, but chlorine damages the membrane, so carbon must come first.
• First step: Check your system’s manual for the membrane’s gallons-per-day size before ordering.

Yes, an RO membrane counts as a cartridge.

It’s rated by the gallons per day it can make, not by micron size, the same Crystal Quest guide notes. So you shop for it differently.

Most reverse osmosis systems also send some water down the drain. A countertop reverse osmosis unit is the no-plumbing way to try one.

Water Filter Cartridge Types at a Glance

Each cartridge type has one main job:

• Spun, string-wound and pleated sediment: stop particles by size.
• GAC: high-flow chlorine, taste and odor reduction.
• Carbon block: chemicals plus fine particles, lead and cysts.
• Catalytic carbon: chloramine and hydrogen sulfide.
• KDF: chlorine and some metals through redox.
• Ion exchange resin: hardness, nitrate or arsenic ions.
• Activated alumina: fluoride and arsenic.
• RO membrane: most dissolved solids.

No one media stops every kind of contamination. That’s why most systems stack several cartridges.

Water Filter Cartridge Sizes: Standard vs Big Blue

Standard water filter cartridges are about 2.5 inches wide, Big Blue cartridges are about 4.5 inches wide, and both come in 10-inch and 20-inch lengths.

Width tells you the job: slim for one tap, wide for whole-house filtration.

A Crystal Quest sizing guide lists standard cartridges at roughly 2.5 inches across in 10-inch and 20-inch lengths, fitting most under-sink and point-of-use housings. The same maker lists jumbo cartridges at around 4.5 inches in diameter, holding more media and flowing more water.

Here’s a real example:

The Pentair Pentek 150467 Big Blue housing on Amazon is listed as taking a 20 x 4.5 inch cartridge and is NSF certified. A slim 2.5-inch cartridge won’t seat in it.

So measure before you order: the length end to end, the outside diameter and the shape of the end caps.

For slim under-sink housings, these 10 inch water filter cartridges cover the common media.

What Micron Rating Should a Water Filter Cartridge Be?

A water filter cartridge’s micron rating should get finer at each stage: coarse for the first stage on gritty water, fine for the last one before your tap. A lower number catches smaller particles but clogs faster.

A micron is a millionth of a meter. A sediment cartridge’s rating tells you roughly the smallest particle it’s built to stop.

Ratings come in 2 kinds. A nominal rating catches most particles at that size, while an absolute rating is a tested, near-total cutoff.

So if you’re protecting an ultraviolet light (UV) unit or an RO membrane, look for “absolute” on the box.

On gritty water, start coarse on the main line and add a finer stage after it. That way, the cheap cartridge takes the beating and the expensive one lasts.

What Order Should Water Filter Cartridges Go In?

Water filter cartridges go in order from coarse to fine: sediment, then carbon, then special media, then the RO membrane.

Reverse that order and the fine stages clog or wear out early.

The same Crystal Quest guide says systems run coarse to fine, with a cheap sediment pre-filter first so the finer, pricier media lasts longer.

For example, a common under-sink RO system runs like this:

1. Sediment cartridge to catch particles.
2. Carbon block to remove chlorine, which would damage the membrane.
3. RO membrane for dissolved solids.
4. Carbon post-filter to polish the taste.

A whole-house setup is shorter: sediment first, then GAC or catalytic carbon, then any specialty stage such as KDF.

In other words, every stage of water filtration should get water that’s already cleaner than what the stage before it saw.

Which Cartridge Types Work Best for Drinking Water and Well Water

For city drinking water, a sediment cartridge plus a carbon block covers most taste, chlorine and grit problems. For well water, start with a heavier sediment stage and add media only for what your test finds.

Your water source decides the starting point, and your test results decide what you add.

City water usually arrives clear but chlorinated.

A slim sediment cartridge and a carbon block under the sink handle most of it. You can build a full drinking water filter setup from there.

Well water is the opposite. It often carries sand, iron, sulfur or hardness, so a sediment filter for well water goes on the main line first.

From there, add catalytic carbon for a sulfur smell, ion exchange resin for hardness at one tap, or an RO membrane for dissolved contaminants.

Before you buy any of them, look up the exact model in the NSF certified product listings. That shows what the cartridge was actually tested to reduce, not just what the box claims.