What is chloramine and why do utilities use it?

Chloramine is a disinfection compound formed by combining chlorine with ammonia. Utilities switched from chlorine to chloramine (monochloramine is the most common form) as a secondary disinfectant starting in the 1990s for two reasons: (1) chloramine is more stable than free chlorine and maintains a disinfection residual further into the distribution system — water in large cities can travel miles from the treatment plant, and chlorine dissipates too quickly; (2) chloramine produces fewer trihalomethanes (THMs) — a class of disinfection byproducts regulated under EPA Stage 2 D/DBP rules. The trade-off: chloramine produces different DBPs (haloacetic acids, NDMA) that have their own health concerns, and it's significantly harder to remove than free chlorine.

Does chloramine evaporate from water if you let it sit?

No. This is the most critical difference between chloramine and free chlorine. Free chlorine dissipates from water by off-gassing — letting tap water sit in an open container for 24 hours removes most free chlorine. Chloramine does NOT off-gas. It is far more stable in water. You can leave chloramine-treated water sitting for days and it will remain essentially unchanged. This matters for aquarium owners (chloramine kills fish), dialysis patients (chloramine in dialysis water causes hemolytic anemia), brewers (chloramine causes medicinal off-flavors in beer), and homebrewers. The only effective at-home removal methods are catalytic activated carbon filtration, Campden tablets (potassium metabisulfite — used by homebrewers), vitamin C (sodium ascorbate), or reverse osmosis.

How do I remove chloramine from tap water?

Standard activated carbon (GAC or basic carbon block) does not reliably remove chloramine — it removes free chlorine well but is ineffective against the chlorine-ammonia bond in chloramine. You need: (1) Catalytic activated carbon — a specialized carbon media that breaks the chloramine bond through a catalytic reaction; most quality under-sink carbon block filters use catalytic carbon (Aquasana AQ-5300+ uses catalytic carbon and is NSF 42/53/401 certified). (2) Reverse osmosis removes chloramine 95%+ via the membrane. (3) Vitamin C (sodium ascorbate powder, 1 gram per 100 gallons) — fast neutralization, used for dechlorination of baths for eczema and chemical sensitivity. (4) Campden tablets (potassium metabisulfite) — 1 tablet per 5 gallons; used by homebrewers.

Is chloramine in tap water dangerous to drink?

At the concentrations used in municipal water (typically 0.5–4 mg/L as Cl2), chloramine poses minimal direct health risk to healthy adults. The primary concerns are: (1) DBPs — chloramine produces haloacetic acids (HAAs) and trace NDMA (N-nitrosodimethylamine), a probable carcinogen, as byproducts. HAAs are regulated under EPA Stage 2 rules at 60 µg/L; NDMA has no MCL but health advisories. (2) Dialysis patients — chloramine must be completely removed from dialysis water; even trace amounts cause hemolytic anemia, which is life-threatening. Dialysis facilities use specialized carbon treatment systems. (3) Aquarium fish — chloramine is toxic to fish at tap water concentrations and does not off-gas from tanks. Chemical dechlorination with a product neutralizing both chlorine and chloramine is required.

How do I know if my city uses chloramine or chlorine?

Contact your water utility directly or check your Consumer Confidence Report (CCR). The CCR will list the disinfectant type. Many utilities that use chloramine note it explicitly because customers frequently ask. You can also test your tap water with a home test strip: DPD-based chlorine test strips measure free chlorine — if they read near-zero even though your water is treated, you likely have chloramine (which reads low on free chlorine strips). A total chlorine test strip measures both free chlorine and chloramine-bound chlorine. If total chlorine is significantly higher than free chlorine, chloramine is present.

How to Remove Chloramine from Drinking Water

Why Chloramine Is Harder to Remove Than Chlorine — and Why That Matters

Approximately 68% of US community water systems that disinfect use chloramine as their secondary disinfectant. If you live in a major city — Denver, San Francisco, Houston, Philadelphia, Seattle, and hundreds of others — your tap water almost certainly contains chloramine, not free chlorine.

This matters because most filter marketing talks about "chlorine removal" without distinguishing between free chlorine (easy to remove with any basic carbon filter) and chloramine (requires catalytic carbon or reverse osmosis). A Brita Standard pitcher with a basic carbon block filter removes free chlorine effectively but is largely ineffective against chloramine. If your utility uses chloramine and you buy a standard carbon pitcher thinking it will remove the disinfectant, you're getting incomplete protection at the very problem you're trying to solve.

The first step is confirming which disinfectant your utility uses. Once confirmed, filter selection becomes straightforward.

Chloramine vs. Free Chlorine: Key Differences

Property	Free Chlorine	Chloramine
Chemical formula	HOCl / OCl⁻	NH2Cl (monochloramine)
Disinfection strength	Strong — kills pathogens rapidly	Weaker — needs longer contact time
Distribution stability	Dissipates over distance	Stable — maintains residual in large systems
Evaporates from water?	✓ Yes — 24-hr off-gassing removes most	✗ No — stable in open containers indefinitely
THM byproducts	High THM formation	Lower THMs — but forms HAAs and NDMA
Taste/odor	Pool-like chlorine taste	Less obvious — some describe as "metallic"
Removed by standard carbon?	✓ Yes — basic GAC effective	✗ No — requires catalytic carbon
Removed by RO?	✓ Yes	✓ Yes — 95%+
Safe for aquariums?	Remove before adding to tank	Must neutralize chemically — does not off-gas
Dialysis patients	Must be removed from dialysis water	Must be completely removed — more difficult

Disinfection Byproducts: The Real Health Concern

Chloramine itself at drinking water concentrations poses minimal direct health risk. The bigger concern is what it forms when it reacts with organic matter in water and plumbing systems — disinfection byproducts (DBPs). Chloramine and chlorine form different DBP profiles:

Haloacetic acids (HAAs)

How it forms: Chloramine reacts with natural organic matter in water (humic acids from soil and decomposed vegetation)

EPA limit: 60 µg/L for HAA5 (five specific HAAs)

Probable carcinogens (bladder cancer association in epidemiological studies). Chloramine produces HAA5 at lower rates than chlorine but produces HAA9 (nine HAAs) at higher rates — and EPA currently only regulates HAA5.

NDMA (N-nitrosodimethylamine)

How it forms: Chloramine reacts with dimethylamine precursors in water — particularly in systems using wastewater reclamation

EPA limit: No MCL — EPA health advisory of 7 ng/L (0.007 µg/L)

Probable carcinogen at very low concentrations. More commonly formed from chloramination than chlorination. RO removes NDMA effectively; activated carbon has limited effectiveness.

Trihalomethanes (THMs)

How it forms: Both chlorine and chloramine react with natural organic matter, but chloramine produces significantly less THMs

EPA limit: 80 µg/L for TTHMs (total trihalomethanes)

The main reason utilities switched to chloramine — lower THM formation. But the trade-off is increased HAAs and NDMA.

See the full disinfection byproducts guide for detailed coverage of THMs, HAAs, and the filter options for each.

Best Filters for Chloramine Removal

The critical distinction: catalytic activated carbon is required for chloramine removal. Standard granular activated carbon (GAC) removes free chlorine well but has limited effectiveness against chloramine. Most Brita, ZeroWater, and PUR standard pitchers use non-catalytic carbon. When comparing filters for a chloramine utility, look specifically for "catalytic carbon" in the media description, or confirm NSF 42 certification with a chloramine-specific challenge (some NSF 42 certs are tested only on free chlorine).

Aquasana AQ-5300+ Under-Sink

NSF 42, 53, 401 · Catalytic activated carbon + KDF media

$149

Chloramine removal: 98.2% chloramine reduction (NSF 42 certified)

Our top pick for chloramine-heavy city water. Triple NSF certification. Catalytic carbon specifically addresses chloramine. Best value under-sink for this problem.

SpringWell CF1 Whole-House

NSF 61 · Catalytic carbon + KDF-55

$449

Chloramine removal: 99%+ free and combined chlorine by design

The best whole-house option for chloramine. KDF-55 catalytic carbon combination is specifically designed for chloramine systems. Protects all taps including shower — important since chloramine exposure through steam inhalation is a separate concern.

AquaTru Classic Countertop RO

NSF 58, P473 · RO membrane + pre/post carbon

$349

Chloramine removal: 95%+ via RO membrane

RO removes chloramine without requiring catalytic carbon media. Best for renters who cannot install under-sink systems. Addresses chloramine, DBPs, PFAS, lead, and nitrates in one system.

Special Populations with Heightened Chloramine Concerns

Aquarium owners

Chloramine is toxic to fish and aquatic invertebrates at tap water concentrations. Unlike free chlorine, it does not off-gas from aquarium water — never add untreated tap water to a fish tank in a chloramine utility.

Solution: Use Seachem Prime ($10) which neutralizes both chlorine and chloramine instantly. Or use catalytic carbon-filtered water from a dedicated aquarium filter setup. See full guide: aquarium water treatment.

Dialysis patients

Chloramine in dialysis water causes methemoglobin formation and hemolytic anemia — a life-threatening reaction because dialysis exposes a large blood volume to water across a semipermeable membrane. This is the most serious health risk associated with chloramine.

Solution: Dialysis centers are required to test dialysis water for chloramine and use specialized treatment (typically two carbon contactors in series). Home dialysis patients must confirm their water treatment system removes chloramine.

Homebrewers and winemakers

Chloramine reacts with phenolic compounds in malt and hops to produce chlorophenols — compounds detectable at parts per billion that create a "medicinal" or "band-aid" off-flavor. This is a common and frustrating problem in homebrew communities. Letting tap water sit overnight does not remove chloramine.

Solution: Campden tablets (potassium metabisulfite, $2/bag) — crush one tablet per 5–10 gallons and stir; neutralizes chloramine in 30 seconds. Or use catalytic carbon-filtered water for all brewing water.

People with eczema / chemical sensitivity

Some individuals with skin conditions or chemical sensitivities report worsening symptoms from chloramine in bath and shower water. Unlike drinking water filtration, shower filtration for chloramine requires catalytic carbon — standard KDF shower filters designed for free chlorine are less effective on chloramine.

Solution: Vitamin C (ascorbic acid) bath treatment — 1,000 mg vitamin C powder per tub neutralizes chloramine and free chlorine. Catalytic carbon shower filter (Aquasana shower filter uses catalytic carbon). See: best shower filters for chloramine.

Check Your Utility Before Buying a Filter

If you're buying a filter specifically for taste, odor, or DBP concerns, confirm whether your utility uses free chlorine or chloramine first. A standard carbon pitcher costs $40–50 and works well for free chlorine — but does almost nothing for chloramine. A catalytic carbon under-sink filter (Aquasana AQ-5300+, $149) handles both. Spending $50 on the wrong filter and then needing to upgrade costs more than buying the right filter once. Your utility's Consumer Confidence Report or a quick phone call to the utility confirms which disinfectant they use.