Chlorine and chloramine

WTR

4.0 mg/LEPA max residual limit (MRDL), chlorine and chloramine

Both disinfectants are held to 4.0 mg/L, a level EPA classes as having no known health risk to drink. The real health question is the byproducts they form, which live on the trihalomethanes and secondary DBP pages.

Aesthetic, not a health concern

Stasis Home ResearchEvery claim on this page is graded against peer-reviewed health research and linked to its primary source.Updated July 2026

Chlorine and chloramine are the disinfectants utilities add to keep tap water free of germs from the plant to your tap, and EPA holds both to 4.0 mg/L, a level with no known health risk to drink. At that residual the disinfectant itself is mostly a taste-and-odor matter. The health story is the byproducts they form, covered in trihalomethanes and secondary DBPs. Aquariums and dialysis are the real exceptions.

What it is, and where it comes from

Chlorine and chloramine are the two disinfectants nearly every US utility uses to keep water free of disease-causing microbes on the trip from the treatment plant to your tap. Free chlorine is the classic one. Chloramine is chlorine combined with a small amount of ammonia, which makes a weaker but far more stable disinfectant that holds its protective residual deep into the distribution system, so many large systems run it instead. The type used in drinking water is monochloramine, not the dichloramine and trichloramine that irritate eyes and give off the sharp smell at indoor pools. Much of Southern California has been on chloramine for decades: the Metropolitan Water District, which wholesales water across the region, disinfects with chloramine rather than free chlorine. These are residuals by design: a deliberate leftover dose that guards the water on the way to you, not a contaminant that slipped in.

Why it matters

The disinfectants earn their keep. Chlorinating drinking water is one of the great public-health wins of the last century, and the residual is what keeps a stray contamination event in the pipes from reaching you. At the regulated cap of 4.0 mg/L, EPA classes both chlorine and chloramine as levels with no known or expected risk to health from drinking, and the evidence for direct harm from the residual itself at these concentrations is limited. The common wellness-blog claim that chloramine is a potent toxin in your glass overstates it. The real health question is not the disinfectant but the disinfection byproducts it forms when it reacts with natural organic matter in the water, the trihalomethanes and the secondary DBPs, which carry their own numbers on their own pages. Three specific caveats are real and worth naming. Chloramine and chlorine are toxic to fish and other aquatic pets, and to anyone on kidney dialysis, because they do damage across gills or in direct contact with blood. They are still safe for you to drink, because drinking routes the water through your digestive tract rather than into direct contact with your blood, but they have to be removed from aquarium water and from the water a dialysis machine uses. And switching a system from free chlorine to chloramine can, in the wrong water chemistry, disturb the protective mineral scale inside old lead pipes and release lead, the mechanism behind Washington DC's 2001 to 2004 lead episode, which is why corrosion control has to move in lockstep with any disinfectant change.

EPA sets a maximum residual disinfectant level (MRDL) of 4.0 mg/L, measured as Cl2, for both chlorine and chloramine, with the goal (MRDLG) also at 4 mg/L, defined as the level below which there is no known or expected risk to health.US EPA, National Primary Drinking Water Regulations (Disinfectants: chlorine and chloramines MRDL 4.0 mg/L, MRDLG 4 mg/L, as Cl2)
Chloramine is made by adding ammonia to chlorine; the type used to disinfect drinking water is monochloramine, and CDC states that chloramine levels up to 4 mg/L are considered safe to drink.CDC, About Water Disinfection with Chlorine and Chloramine
EPA advises that chlorine and monochloramine must be removed from water used in kidney dialysis machines and from aquarium water, because dialysis puts the water in direct contact with blood and in fish it enters the bloodstream through the gills, while EPA states the same water is safe to drink.US EPA, Can Chloraminated or Chlorinated Water Be Used for Dialysis or Aquarium?
A utility switch from free chlorine to chloramine triggered the excessive lead in Washington DC drinking water; bench testing showed chlorine forms an insoluble lead solid that stabilizes pipe scale, a solid that does not form under chloramine, which helps explain the lead release.Edwards and Dudi, 2004 (Journal AWWA 96(10):69-81; role of chlorine and chloramine in corrosion of lead-bearing plumbing materials)
The Metropolitan Water District of Southern California, which wholesales water to much of the region, disinfects with chloramine, so much of Southern California has been on chloramine for decades.LA County Public Works, Questions and Answers about Chloramines (MWD 1985 conversion from chlorine to chloramine)
Standard activated carbon removes free chlorine quickly, but chloramine breaks down far more slowly on carbon, so removing it reliably calls for catalytic carbon with several times the contact time, or reverse osmosis; simply letting water sit does not off-gas chloramine the way it does free chlorine.Water Quality Association, Chloramine Fact Sheet (catalytic carbon and contact time)

What we grade it against

Where the health research draws the line, versus the legal limit.
Contaminant	Health-based level	Legal limit	Source (health-based)
Chlorine (mg/L, as Cl2)	4MRDLG, the level with no known or expected risk to health	4.0MRDL, enforceable; here the health goal and the legal limit are equal, unlike a carcinogen	US EPA National Primary Drinking Water Regulations
Chloramine (mg/L, as Cl2)	4MRDLG, same basis as chlorine	4.0MRDL, enforceable; identical to the chlorine limit	US EPA National Primary Drinking Water Regulations

Health-based levels come from peer-reviewed research and government risk scientists working without cost constraints. Legal limits are enforceable compromises. Your report grades to the health column.

What helps

Direct fixes

Under-sink reverse osmosis (RO) at the kitchen tap (NSF/ANSI 58)
Removes both free chlorine and chloramine along with the byproducts they form, plus PFAS, lead, and most heavy metals, at the tap you drink and cook from. The most complete single fix when the goal is clean drinking water.
Catalytic carbon block at the tap (NSF/ANSI 42)
Catalytic carbon is engineered to break chloramine down, not just adsorb it, and with enough contact time it handles chloramine as well as free chlorine for taste, odor, and residual.
It needs the longer contact time to work on chloramine; a fast-flow faucet filter sized only for chlorine will leave chloramine behind. A whole-house catalytic carbon unit is the larger retrofit when the goal is chloramine-free water at every fixture.

Free and behavioral

Standard activated carbon pitcher or faucet filter
Good and cheap for free chlorine: it takes out the chlorine taste and smell in a single pass.
Not reliable for chloramine, which passes through standard carbon without the catalytic media and contact time it needs. If your utility uses chloramine (much of Southern California does), a basic pitcher is a taste fix, not a chloramine fix.
Dechloraminating conditioner for aquariums, and dialysis-grade treatment for dialysis water
If you keep fish or other aquatic pets, use a water conditioner that specifically neutralizes chloramine, not one rated for chlorine only, since chloramine does not dissipate on standing. Dialysis water is treated at the clinic with carbon and ascorbic acid; this is the one context where the disinfectant genuinely must be removed for health.

We are not going to sell you a chloramine scare. The chlorine and chloramine in your water are there on purpose, and reliable disinfection is a big part of why waterborne disease is rare in the US. At the levels utilities are held to, the residual itself is a taste-and-smell question, not a health threat, and the framing of chloramine as a toxin in your glass gets it wrong. Where we do lean in is precise. The byproducts these disinfectants form are the real health story and live on their own pages, aquarium and dialysis water genuinely need the chloramine removed, and a badly managed switch to chloramine can pull lead out of old pipes. A good catalytic-carbon or RO setup takes the taste and the residual out at the tap, and it is doing more useful work on the byproducts than on the disinfectant itself.

Common questions

Is chlorine in tap water safe to drink?

Yes, at the levels US utilities use. EPA holds chlorine and chloramine to a maximum residual of 4.0 mg/L, a level it classes as having no known or expected risk to health from drinking. The residual is what keeps your water free of germs all the way to the tap, so it is doing a job. If you dislike the taste, a carbon filter removes it. The health question worth attention is not the disinfectant itself but the byproducts it forms, covered under trihalomethanes and secondary DBPs.

What is chloramine and why does my water smell like a pool?

Chloramine is chlorine combined with a small amount of ammonia, a more stable disinfectant that many large systems, including much of Southern California, use to hold a residual across long pipe networks and to form fewer regulated byproducts than free chlorine. The type in your water is monochloramine. A faint pool or chemical smell is the residual itself and is normal, not a sign the water is unsafe. A carbon filter reduces it. Worth knowing: the strong smell at an actual pool comes from trichloramine in the air above the water, a different compound from the monochloramine dissolved in your drinking water.

How do I remove chlorine or chloramine from water?

Free chlorine is easy: a standard activated carbon filter or pitcher removes it, and it even off-gasses if you let a glass sit out. Chloramine is harder. It breaks down slowly on carbon and does not dissipate on standing, so it needs catalytic carbon with a longer contact time, or reverse osmosis. For drinking and cooking, an under-sink RO or a certified catalytic carbon filter handles both. If your utility runs chloramine, confirm the filter is rated for chloramine specifically, not chlorine only.

Is chloramine bad for my fish or for dialysis?

Yes, and this is the one place the caution is real. Chloramine and chlorine are toxic to fish and other aquatic pets because they cross the gills straight into the bloodstream, and they are toxic to anyone on kidney dialysis because the machine puts water in direct contact with blood. Both must be removed from aquarium water (use a conditioner that neutralizes chloramine, not just chlorine, since chloramine will not dissipate on its own) and from the water a dialysis machine uses. The same water stays safe for you to drink, because drinking routes it through your digestive tract rather than into direct contact with your blood.