A filter comparison chart is only useful if the columns are things a manufacturer must state and a buyer can check. Most published comparison charts fail on that test, because they compare price and brand rather than mechanism and rating. Here are the columns that actually decide the outcome, and the one column you will not be able to fill in for anybody.
- Absolute micron rating is the single most decision-relevant column, and it is the one most often missing.
- Rated capacity in gallons matters more than a marketed replacement interval in months.
- Record whether the NSF/ANSI 401 listing names Microplastics Reduction specifically, not merely whether the unit is certified.
- Note the mechanism, since a membrane and a carbon block are different kinds of barrier regardless of price.
Column One: Mechanism
Start here because it constrains everything downstream. Granular activated carbon, compressed carbon block, hollow-fibre ultrafiltration and reverse osmosis are different physical processes. Reviews of media filtration in drinking water treatment describe removal occurring through screening, interception, adsorption, size exclusion, cake formation and electrostatic attraction or repulsion [1], which is a useful reminder that adsorption and size exclusion are not the same thing and a product strong at one may be weak at the other.
Column Two: Absolute Micron Rating
Record the number and whether it is nominal or absolute. Nominal describes typical performance under test conditions. Absolute describes a hard cutoff. A product quoting only a nominal figure is quoting a softer claim, and a product quoting no figure at all should be entered as unrated rather than as unknown, because a manufacturer that measured it would publish it.
Size context helps you interpret the number. Particles measured in indoor air studies have spanned 20 to 5,000 micrometres in one survey [2] and 1 to 10 micrometres in another targeting the inhalable fraction, where 94 percent were below 10 micrometres and counts rose sharply as size fell [3]. In water, nanoplastic work deals with particles below one micrometre entirely [4]. A five micron filter is meaningful against fibers and meaningless against nanoplastics.
Column Three: Rated Capacity in Gallons
Capacity is the honest replacement metric, and marketed intervals in months are derived from a usage assumption that may not match yours. Enter the gallon rating, then compute your own interval from your household draw. Two products at the same price with capacities of 100 gallons and 19,000 gallons are not remotely comparable, and a chart sorted by unit price will rank them backwards.
Column Four: Cost Per Gallon
Divide replacement cartridge cost by rated capacity. This is the column that turns a confusing set of prices into a single comparable number, and it frequently inverts the ordering that sticker price suggests. Include the initial system cost amortised over an assumed ownership period if you want the full picture, though the cartridge figure alone is usually enough to make the decision.
Column Five: Certification, and the Exact Claim
This column needs two cells, not one, and collapsing them is where most comparison charts go wrong. The first cell is which standard the unit is certified against. The second is which individual claims that listing actually names. Microplastics Reduction is a claim available under NSF/ANSI 401, the emerging contaminants standard, but a unit listed under 401 does not automatically carry it. It may be listed for pharmaceuticals or hormones and not for particles.
So the entry that belongs in your chart is not certified under 401. It is listing names Microplastics Reduction for model X with cartridge Y, or it does not. Certification is issued by several accredited bodies including NSF, IAPMO, the Water Quality Association and Intertek, so the issuing mark varies while the standard does not.
Record the tested size basis alongside it. The Microplastics Reduction claim is evaluated at roughly 0.5 to 1 micrometre and above, which means it does not speak to nanoplastics below one micrometre at all [4]. A chart that records the claim without the size floor overstates what the certification covers.
Column Six: Flow Rate and Practical Constraints
Record flow rate, whether a storage tank is required, whether a drain connection is needed, and the physical space required. Reverse osmosis performs the tightest rejection available at point of use and carries all four constraints. Ultrafiltration carries fewer. A pitcher carries none and buys correspondingly less.
The Column You Probably Will Not Fill
There is no column for measured microplastic removal in your home, because almost nobody will measure it. Doing so means mail-in laboratory analysis of a sample taken before and after the filter, at several hundred dollars each. Verification would require the laboratory methods used in the research literature, spanning infrared and Raman spectroscopy, electron microscopy and mass spectrometry [5]. Leave that column out entirely rather than filling it with a manufacturer’s percentage claim, which will have been produced under test conditions you cannot reproduce and at a size cutoff that may not be stated [6].
A Minimal Working Chart
- Product and mechanism
- Micron rating, and nominal or absolute
- Rated capacity in gallons
- Replacement cartridge cost and resulting cost per gallon
- Standard certified against, and whether the listing names Microplastics Reduction
- Flow rate, tank required, drain required, space required
FAQ
What if a product will not publish a micron rating?
Treat it as unrated. A manufacturer that had a favourable number would print it.
Should percentage removal claims go in the chart?
Only with the size range and test method attached. Without those, a percentage is not interpretable [7]. A third-party certification listing is stronger evidence than a self-reported percentage, because the test conditions are standardised.
Is whole-house better than under-sink?
Different jobs. Whole-house handles sediment and chlorine at the point of entry. The tightest barriers are point-of-use because they operate at low flow.
A comparison chart compares specifications. It cannot compare outcomes in your home, because no home measurement of microplastics is possible.
References
- Research Progress on Removal of Microplastics by Filtration in Drinking Water Treatment. Huan Jing Ke Xue (2025). PMID 40962783
- Microplastics in Australian indoor air: Abundance, characteristics, and implications for human exposure. Sci Total Environ (2023). PMID 37211105
- Human exposure to PM10 microplastics in indoor air. PLoS One (2025). PMID 40737229
- Nanoplastics removal during drinking water treatment: Laboratory- and pilot-scale experiments and modeling. J Hazard Mater (2022). PMID 35643007
- Analytical methods for microplastics in the environment: a review. Environ Chem Lett (2023). PMID 36196263
- Microplastics: A review of analytical methods, occurrence and characteristics in food, and potential toxicities to biota. Sci Total Environ (2022). PMID 34571218
- Microplastics and nanoplastics in tea: Sources, characteristics and potential impacts. Food Chem (2025). PMID 39608112
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.
