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Chlorine and Chloramine in Tap Water

Written and reviewed by the BWF Team, a certified water specialist, a former municipal plant operator, a licensed plumber and a former system dealer.

Chlorine and chloramine are two different disinfectants, and NSF certifies them as two different claims. 5,553 certified models hold chlorine reduction under NSF/ANSI 42. 216 hold chloramine reduction. Roughly a twenty-six to one gap, on the same standard.

Many US utilities disinfect with chloramine rather than chlorine, and it is the harder of the two to remove: it does not gas off if you leave a jug standing, and it takes catalytic carbon or a much longer contact time. So if your supply is chloraminated, the second number is the one that applies to you, and your water report says which you have.

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Two disinfectants, two claims

Nearly every filter sold mentions chlorine, because chlorine taste is the single most common reason anyone buys one. Chloramine gets mentioned far less, and it is in a great deal of tap water.

Chlorine Chloramine
What it is Chlorine gas or hypochlorite, the traditional disinfectant Chlorine combined with ammonia, more stable in the pipes
Why a utility picks it Fast acting and cheap, but it dissipates along the network Lasts to the far end of the system and forms fewer regulated by-products
How it behaves at your tap Smells like a swimming pool. Standing water or a jug in the fridge loses much of it Less obvious a smell, and it does not gas off the way chlorine does
What removes it Ordinary activated carbon, quickly Catalytic carbon, or ordinary carbon with much longer contact time
Certified models 5,553 under NSF/ANSI 42 216 under NSF/ANSI 42

The clearest way to see the gap is inside a single brand. Of Waterdrop's listings in NSF's database, 396 models carry the chlorine claim and exactly one carries the chloramine claim. Nothing is being hidden: those products were submitted for the test they were submitted for, and the record says so plainly. It is just not the thing a shopper reads off a box.

Which one is in your water

Your supplier publishes it every year and it is free. The annual water quality report, sometimes called a Consumer Confidence Report, names the disinfectant they use. Search your utility's name with "water quality report" and it takes about a minute to find.

It is worth the minute for more than this question. That document also tells you the things that decide whether you need a lead filter, a membrane or nothing more than a carbon cartridge, and it is the difference between choosing a filter and guessing at one.

Why chloramine is the harder one

Chlorine is reactive and impatient. It attacks carbon quickly, which is why an ordinary carbon filter deals with it easily, and why a jug left standing in the fridge loses much of it on its own.

Chloramine is built to be stable, which is exactly why utilities like it: it survives the journey to the far end of the network. That same stability is what makes it awkward at your tap. It does not gas off, standing does not help, and removing it takes either catalytic carbon, which is treated to be more reactive, or ordinary carbon with far more contact time than a fast-flowing filter gives it.

This is why the two claims are separate on the certificate rather than bundled. They are genuinely different tests of a genuinely different job.

What to look for

If your report says chloramine, the thing to check is whether chloramine is named in a filter's certified claim list, not whether the box says chlorine. Certifiers publish that list by model number, and it is the same two-minute check that answers every other question on this site.

Products certified for it do exist and some are inexpensive. The Brondell Coral UC300 carries chloramine on its WQA listing under standard 42, alongside lead and PFAS under standard 53, and it is an under-sink carbon system rather than a reverse osmosis one. Several manufacturers also sell cartridges specifically marketed for chloramine, which is a reasonable place to start if you already own a housing.

Reverse osmosis is the other route. An RO system puts carbon stages in front of the membrane and gives the water far more contact time than a tap-mounted filter does, which is why RO is a dependable answer to taste and smell whatever the disinfectant is.

Common questions

What is the difference between chlorine and chloramine?
Chlorine is the traditional disinfectant and chloramine is chlorine combined with ammonia. A utility choosing chloramine gets a disinfectant that survives to the far end of the network and produces fewer regulated by-products, which is why many have switched. For anyone filtering water at home the practical difference is that chloramine is more stable: it does not gas off if you leave a jug standing, and it takes catalytic carbon or a much longer contact time to remove.
Do water filters remove chloramine?
Some do, and far fewer than remove chlorine. NSF certifies the two separately under standard 42, and on our reading of their database 5,553 models hold the chlorine claim against 216 for chloramine. So a filter certified for chlorine has not necessarily been tested for chloramine, and if your supply is chloraminated it is the second number that applies to you. Look for chloramine named in the claim list rather than assuming.
How do I know if my water has chlorine or chloramine?
Your water supplier publishes it every year, free, in the annual water quality report, sometimes called a Consumer Confidence Report. It names the disinfectant used. Searching your utility name with "water quality report" finds it in about a minute, and it is the single most useful document for anyone choosing a filter, because it also tells you what else is in the supply.
Is chlorine in tap water harmful?
Chlorine in a public supply is there deliberately and at levels regulated to be safe, and it is the reason the water is microbiologically safe to drink at all. Most people filtering it are doing so because of taste and smell rather than a health worry, which is a perfectly good reason and is exactly what NSF/ANSI 42 certifies against. The by-products of disinfection are a separate subject and sit under standard 53.
Does boiling remove chlorine?
Boiling drives off a good deal of free chlorine, and letting water stand does much of the same over a few hours. Neither works nearly as well on chloramine, which is more stable and does not readily leave the water, and that difference is the practical reason chloramine is the harder of the two to deal with at home.
Does a shower filter remove chlorine?
That is what shower filters are built for, and there is a standard written for exactly it: NSF/ANSI 177, whose single claim is free available chlorine reduction. Only nine certified models held it when we checked, and its one claim is chlorine rather than chloramine. Our certification research covers what that means for the category.

How we checked

Both counts were read from NSF's public database on 6 August 2026 and can be re-run with one command. The claim names come from NSF's own search form, which is the authority on what can be certified at all and lists 151 claims across seven standards. Chlorine Reduction and Chloramine Reduction are two of them, both under standard 42.

The query carried a control, because a count only means something if the same method finds things elsewhere. The chlorine figure of 5,553 is itself that control for the chloramine figure of 216: one query shape, one session, two very different answers.

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