Filters certified for trihalomethanes — 153 models, and four at the main

By Andrew Bates, FounderPublished 2026-09-10Updated 2026-09-11

153 distinct models from 23 companies held an NSF/ANSI 53 trihalomethanes reduction claim on 2026-09-10. But 149 of them are point-of-use and four are point-of-entry — which sits awkwardly against EPA naming byproducts as something you inhale in the shower.

Where the exposure is, and where the products are

EPA is specific about why byproducts are different from most contaminants on this site. They are among the things that “easily turn into gases and may pose a risk when inhaled, such as when showering”, and EPA says a point-of-entry device can reduce them.

That is an argument for treating the main.

The certified market says something else:

Category	Models
Plumbed-in to separate tap	56
Faucet mount	29
Counter-top connected to sink faucet	24
Plumbed-in	21
Refrigerator filter	18
Pour-through (pitcher)	1
Point-of-entry (whole-house)	4

149 of 153 certified models treat one tap. Four treat the main, and all four are listed under a single company.

So the exposure route EPA identifies has almost no certified products addressing it. That is a fact about what manufacturers have certified, not about what works — but it is the fact a buyer runs into.

→ Disinfection byproducts: the limits, and the report figure that is an average

The four at the main

The four point-of-entry models holding a trihalomethanes claim are the same four Aquion RainSoft units that hold the only point-of-entry VOC claim. Searching trihalomethanes separately turned up no additional whole-house product.

That matters because of what a VOC claim is. NSF states a VOC reduction claim means the system reduces the concentration of every contaminant in a defined list, and that the category “also includes total trihalomethanes, which are a by-product of chlorination.”

So those four hold the byproduct group twice over — once by name, once inside the bundle.

→ What a whole-house filter is certified to do

If a supplier offers you a different whole-house system for byproducts, the question is which accredited body certified it and for which claim.

→ How to read an NSF listing, footnotes included

What the claim covers, and what it leaves out

A trihalomethanes claim covers the group EPA regulates as total trihalomethanes: chloroform, bromodichloromethane, dibromochloromethane and bromoform, capped together at 0.080 mg/L.

It does not cover the other regulated byproduct group. HAA5 — the five haloacetic acids, capped at 0.060 mg/L — has no NSF reduction claim of that name. A product certified for trihalomethanes says nothing about haloacetic acids either way.

Both figures appear on your annual report, and only one of them has a corresponding certification to shop for.

→ How to read your water quality report

The decision framework

1. Settle the exposure route, knowing the market does not match it

If ingestion is your concern, 149 models hold the claim and this is an ordinary purchase.

If inhalation in the shower is your concern, EPA’s framing points at the main and the certified field is four models from one company. That is a real constraint, not a reason to substitute an uncertified product.

If both, the four whole-house models are the only certified way to cover the route EPA names, and a point-of-use filter still covers what you drink.

2. Read your figures before buying

TTHM and HAA5 both appear on the annual report, and both are locational running annual averages rather than what came out of your tap on any day. A figure near the limit is the one most affected by how it was calculated.

3. Pick the format, where this claim is unusually flexible

Faucet mounts hold 29 of the 153 — far better representation than on cyst reduction, where one faucet mount holds the claim. If you want something cheap and removable, this is one of the few claims where that exists.

→ Which claims exist at all, and how populated each is

4. Check the claim on the model

Claims vary by product and are listed per model. Some NSF entries carry the footnote “conforms to the material requirements only”, which places a product under a standard with no reduction claim at all.

Applying the framework: who holds the claim

Company	Models
Kaz USA (Helen of Troy)	29
Access Business Group (Amway)	26
Whirlpool Corporation	14
Solventum Purification Inc.	13
Brio Water Technology	12
Pentair Residential Filtration	8
Multipure	7
Water Channel Partners	6
Aquion, Inc.	5
Amway (China)	4

The remaining 13 companies hold three or fewer models each.

Notes tied back to the criteria

Kaz USA holds all 29 faucet mounts in this claim, as it did for lead. If the faucet-mount route matters to you, the certified choice is narrow by company even though 29 models is not a small number.
Aquion’s five include the four point-of-entry models, which is the entire certified whole-house option for this claim.
One pour-through model. Pitchers are effectively absent from this claim, unlike microplastics where 64 hold it.
Nothing here separates models on performance. NSF records claim membership, not a reduction percentage.

The decision path

Your situation	What decides it	Where that lands you
TTHM near the limit, concerned about drinking	Ingestion route	149 point-of-use models
Concerned about the shower	EPA names inhalation	Four models, one company
Want something cheap and removable	Faucet mount, 29 models	Unusually well covered here
Want a pitcher	One model holds the claim	Change format, or search by claim
Worried about HAA5 as well	No claim of that name exists	Nothing certified to shop for
Offered another whole-house unit	Four are certified	Ask which body and which claim
No figures yet	Nothing to size	Read the annual report

Choose a point-of-use filter if

Your concern is what you drink. 149 models hold the claim across five formats.
You want a faucet mount, which this claim supports better than most.

Choose one of the four whole-house models if

Your concern is the inhalation route EPA names, and you want it certified.
You accept that the certified field is four models under one company, and that they carry the VOC bundle as well.

Choose to do nothing if

Your reported TTHM figure sits well below 0.080 mg/L and the shower does not concern you. There is no second problem this purchase solves.

Mistakes that cost the most money

Buying point-of-use for a shower concern. It treats the water you drink and does not reach the route EPA names for byproducts.

Buying whole-house for byproducts without checking the claim. Four point-of-entry models hold a trihalomethanes claim. Everything else in that category is certified for chlorine, taste and odour or sediment.

Assuming a TTHM claim covers HAA5. It does not, and no claim of that name exists to look for.

Reading a compliant annual figure as your tap water. Both byproduct figures are locational running annual averages.

Treating the disinfectant as the problem. The residual is protecting water through the distribution system; the byproducts are the regulated endpoint.

→ Chlorine and chloramine, and why the residual is there

Forgetting cartridge replacement. EPA states carbon filters have a specified shelf life and should be replaced on schedule.

Three situations, and what changes

Chlorinated surface water supply, figures in the upper half. The case where both routes are live. A point-of-use filter covers drinking cheaply; the shower route has four certified options and that is the whole market.

You were about to buy a shower filter for byproducts. That standard offers one claim, free available chlorine, and no byproduct claim at all. This claim is where the certified products for byproducts actually are.

→ Shower filters: one standard, one claim

Your report lists HAA5 above TTHM. Nothing certified addresses HAA5 by name. The honest answer is that the shopping question has no certified answer for that group, and the utility-side controls are where it gets managed.

The objections worth answering

“If EPA says treat the main, why is almost nothing certified for it?” A fair question this page cannot answer, because NSF records what manufacturers submitted for certification and not why. The gap is reported rather than explained.

“Four models is not a market.” It is not. That is the finding, and it is better known before a purchase than after.

“My whole-house carbon filter must reduce byproducts.” It may. Without a listed claim there is nothing to verify, and the certified whole-house population for this claim is four models.

“These figures will move.” They will. NSF dates its listings and asks readers to confirm status at source, which is why the capture date sits beside every figure here.

Who this is for

Anyone who has read that byproducts are a shower exposure and wants to know what is actually certified to address it, and anyone choosing a drinking filter with TTHM on their report.

It names no recommended product.

What to settle first

Is my concern what I drink, or what I breathe in the shower?

For the first, 149 certified models. For the second, four. The answer changes the purchase completely, and the market makes one of them much harder than the other.

→ Disinfection byproducts: the limits and the averaging → What a whole-house filter is certified to do → Which claims exist at all, and how populated each is → HAA5 and 32 other regulated contaminants with no claim to shop for → The VOC bundle, which covers trihalomethanes by group and by member

The bottom line

Decide the exposure route first, because the certified market does not match it. If your concern is what you drink, 149 point-of-use models hold a trihalomethanes claim and faucet mounts are unusually well represented at 29. If your concern is what you inhale in the shower — which is the route EPA names for byproducts — four point-of-entry models hold the claim, all from one company, and they hold the VOC bundle as well. That gap is real, and worth knowing before a salesperson fills it with something uncertified.

Who this is not for

This covers the NSF/ANSI 53 trihalomethanes claim only. It says nothing about the five haloacetic acids, the other regulated byproduct group, for which NSF offers no claim of that name. It does not say how well any model performs, and it cannot tell you your own figures — those come from your annual report. NSF listings only, and no distillation system can appear in a claim-search roster because NSF offers no selectable claims under its distillation standard.

Questions

Which filters are certified to reduce trihalomethanes?

NSF listings returned 317 rows for trihalomethanes reduction under NSF/ANSI 53 on 2026-09-10, resolving to 153 distinct models from 23 companies. Most are point-of-use: 56 plumbed-in to a separate tap, 29 faucet mounts, 24 counter-top and 21 plumbed-in.

Is there a whole-house filter certified for trihalomethanes?

Four models, all listed under one company. They are the same four point-of-entry models that hold a VOC reduction claim, so searching trihalomethanes as a separate claim turned up no additional whole-house option.

Should I treat the tap or the whole house for byproducts?

EPA names disinfection byproducts among contaminants that turn into gases and may pose a risk when inhaled while showering, and says a point-of-entry device can reduce them. The certified population sits overwhelmingly at the tap, so the two point in different directions.

Does a VOC reduction claim cover trihalomethanes?

NSF states a VOC reduction claim means the system reduces the concentration of every contaminant in a defined list, and that the category also includes total trihalomethanes. The four whole-house models here hold both claims.

What does a TTHM claim actually cover?

The group EPA regulates as total trihalomethanes: chloroform, bromodichloromethane, dibromochloromethane and bromoform, capped together at 0.080 mg/L. A report line reading TTHM is the sum of those four compounds rather than one.

Are haloacetic acids covered too?

Not by this claim. HAA5 is the other regulated byproduct group, capped at 0.060 mg/L, and NSF offers no reduction claim of that name. A trihalomethanes claim says nothing about it either way.

Do pitchers reduce trihalomethanes?

Almost none are certified to. One pour-through model held the claim on 2026-09-10 out of 153. Faucet mounts are far better represented in this claim at 29 models, which is unusual among the claims covered on this site.

Why does my water have trihalomethanes at all?

They form when the disinfectant that makes water microbially safe reacts with organic material already in it. EPA names trihalomethanes, haloacetic acids, chlorite and bromate as byproducts of that reaction, and limits them rather than banning disinfection.

Sources — 15 claims

NSF Official Listings — Drinking Water Treatment Units, NSF/ANSI 53 trihalomethanes (TTHM) reduction claim search (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
NSF listings returned 317 rows for trihalomethanes reduction under NSF/ANSI 53 on 2026-09-10, resolving to 153 distinct model designations from 23 companies. (captured 2026-09-10)
Limits: NSF lists some models on several rows, so row counts and distinct-model counts measure different things and both are reported. NSF listings only.
NSF Official Listings — Drinking Water Treatment Units, NSF/ANSI 53 trihalomethanes (TTHM) reduction claim search (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
Of 153 distinct models holding an NSF/ANSI 53 trihalomethanes reduction claim on 2026-09-10, 149 are point-of-use — plumbed-in to separate tap 56, faucet mount 29, counter-top 24, plumbed-in 21, refrigerator filter 18, pour-through 1 — and 4 are point-of-entry. (captured 2026-09-10)
Limits: Category labels are NSF own, normalised for spelling variants. EPA names disinfection byproducts among contaminants that turn into gases and may be inhaled while showering, an exposure route point-of-use treatment does not reach; this records where the certified products are, not which placement is correct.
NSF Official Listings — Drinking Water Treatment Units, NSF/ANSI 53 trihalomethanes (TTHM) reduction claim search (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
The four point-of-entry models holding an NSF/ANSI 53 trihalomethanes reduction claim on 2026-09-10 are the same four Aquion models that hold the point-of-entry VOC reduction claim; searching trihalomethanes as a thirteenth claim found no additional point-of-entry product. (captured 2026-09-10)
Limits: Two health-related claims held by one set of four models under one company. It widens what those four are certified for and adds no new whole-house option, and thirteen claims is still not every claim NSF offers.
NSF Official Listings — Drinking Water Treatment Units, reduction-claim searches filtered to the Point-of-Entry category (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
NSF states that a VOC reduction claim means the system reduces the concentration of every contaminant in a defined list, and that the VOC category also includes total trihalomethanes, a byproduct of chlorination. (captured 2026-09-10)
Limits: A bundle claim covering a defined list, not a claim about any concentration or removal percentage. The list quoted here is truncated at the point the source text was captured and is longer than shown.
NSF Official Listings — Drinking Water Treatment Units, reduction-claim searches filtered to the Point-of-Entry category (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
Collecting point-of-entry rows across four NSF reduction-claim searches on 2026-09-10 gives 62 distinct point-of-entry model designations from 14 companies, holding chlorine reduction (59), taste and odor reduction (55), nominal particulate reduction (12 across Classes I, III and V) and VOC reduction (4). (captured 2026-09-10)
Limits: A census across searched claims, not across every claim NSF offers. NSF provides no category filter, so point-of-entry products are reachable only by searching a claim and filtering results; a point-of-entry product holding only an unsearched claim would not appear here.
NSF Official Listings — Drinking Water Treatment Units, reduction-claim searches filtered to the Point-of-Entry category (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
VOC reduction and trihalomethanes reduction are the only health-related claims among those searched with any point-of-entry presence: four point-of-entry models hold both, all listed under one company, Aquion, Inc. (captured 2026-09-10)
Limits: Four model designations under one company on one date, holding two health-related claims between them. Trihalomethanes was searched after the original twelve and returned the same four models, adding no new whole-house option. Thirteen claims is still not every claim NSF offers.
NSF — NSF/ANSI 42, 53 and 401: Filtration Systems Standards (page dated 2025-12-16)
Under NSF/ANSI 42 and NSF/ANSI 53, certification claims vary by product; certification to the standard does not mean a product carries every claim available under it. (captured 2026-09-09)
Limits: NSF does not print 'claims vary by product' under NSF/ANSI 401. See certification-nsf-0008 for the 401 position, which rests on weaker source language.
NSF Official Listings — Drinking Water Treatment Units (listings current as of Thursday, September 10, 2026, 12:15 a.m. Eastern Time)
NSF Official Listings mark some entries "Conforms to the material requirements only", meaning the product appears under a standard without any contaminant reduction performance claim having been certified. (captured 2026-09-10)
Limits: The footnote states what was evaluated, not what the product does. It does not say the product performs badly, only that performance was not the basis of this listing. A separate listing for the same model can carry performance claims.
NSF Official Listings — Drinking Water Treatment Units, reduction-claim search form (captured 2026-09-10)
NSF lists NSF/ANSI 62 as Drinking Water Distillation Systems but offers no selectable reduction claims under it in its listing search, which offers claims only under standards 42, 44, 53, 55, 58, 177 and 401. (captured 2026-09-10)
Limits: A property of how NSF indexes claims, not of distillation. Any roster built by searching reduction claims therefore cannot surface a distillation system, so the absence of distillers from such a roster is an artefact of the method and says nothing about what a distiller removes.
EPA — National Primary Drinking Water Regulations
EPA sets a Maximum Contaminant Level of 0.080 mg/L for total trihalomethanes and 0.060 mg/L for the five haloacetic acids, both byproducts of drinking water disinfection. (captured 2026-09-10)
Limits: These are enforceable health-based limits for public water systems, measured as system-wide running averages rather than at an individual tap.
EPA — Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules
EPA states that disinfectants can react with naturally-occurring materials in water to form byproducts including trihalomethanes, haloacetic acids, chlorite and bromate. (captured 2026-09-10)
Limits: Names the formation route and the four byproduct groups. It does not say how much forms, which varies with the disinfectant, the amount of organic material, temperature and time in the pipes.
EPA — Comprehensive Disinfectants and Disinfection Byproducts Rules (Stage 1 and Stage 2): Quick Reference Guide, EPA 816-F-10-080, August 2010
EPA lists the total trihalomethanes group as chloroform, bromodichloromethane, dibromochloromethane and bromoform, and the five haloacetic acids as monochloroacetic, dichloroacetic, trichloroacetic, bromoacetic and dibromoacetic acid. (captured 2026-09-10)
Limits: Composition only. The per-compound MCLG column of EPA’s Table 2 did not survive text extraction from the PDF and is deliberately not recorded here; the enforceable limits are the group totals in contaminant-epadis-0002.
EPA Office of Water — Home Water Treatment Facts / Filtration Facts (published November 2005)
EPA states that for most contaminants a point-of-use device treats only the water consumed, but that contaminants such as radon, disinfection byproducts and some organic chemicals easily turn into gases and may pose a risk when inhaled, such as when showering, which a point-of-entry device can reduce. (captured 2026-09-10)
Limits: States when whole-house treatment is warranted by exposure route. It does not establish that any particular home has volatile contaminants, which requires a test.
EPA — Filtration Facts (Water Health Series), EPA 816-K-05-002
EPA maps disinfection byproducts to point-of-entry adsorptive media systems, distillation, aeration, carbon filtration and reverse osmosis. (captured 2026-09-10)
Limits: A technology list, not a product recommendation. Whether a given model reduces byproducts is a certified claim on that model, and EPA names no capacity, contact time or replacement interval here.
EPA Office of Water — Home Water Treatment Facts / Filtration Facts (published November 2005)
EPA states that an activated carbon filter by itself is not designed to remove all disease-causing organisms, and that carbon filters have a specified shelf life and should be replaced regularly per the manufacturer instructions. (captured 2026-09-10)
Limits: Concerns activated carbon as a class. Some carbon blocks carry certified cyst reduction claims, which is a model-specific capability rather than a property of carbon.