Chloramine vs Chlorine: What's in Your Tap Water? (2026)

📅 Last Updated: July 16, 2026

Published January 2026 | Written by Filter Tested Editorial Team | Last updated: July 11, 2026 | Read our methodology

Last updated: January 2026 | Reading time: 12 minutes

Since 1908, when Jersey City became the first U.S. municipality to chlorinate its drinking water supply, American water utilities have relied on chlorine-based disinfectants to prevent waterborne diseases like cholera and typhoid. But starting in the 1970s, a growing number of cities began switching from free chlorine (Cl-) to chloramine (NH-Cl) - a chemical cocktail of chlorine and ammonia. By 2026, over one in five Americans (roughly 68 million people) receive water treated with chloramine, including residents of Los Angeles, San Francisco, Washington D.C., Dallas, and Philadelphia.

This shift matters enormously for your health, your plumbing, and your water filter purchase. Chlorine and chloramine behave differently in distribution systems, create different disinfection byproducts, require different filtration technologies, and carry distinct health implications. If you bought a standard activated carbon filter thinking it would handle your local water disinfectant, you might be in for an unpleasant surprise.

Quick Verdict

Side-by-Side Comparison: Chlorine vs Chloramine

What Is Chlorine? The Century-Old Standard

When water treatment plants add chlorine gas (Cl-), calcium hypochlorite (Ca(ClO)-), or sodium hypochlorite (NaOCl - liquid bleach) to water, they introduce a powerful oxidizing agent that destroys bacteria, viruses, and protozoan cysts by disrupting cell walls and denaturing enzymes. The "free available chlorine" in treated water exists primarily as hypochlorous acid (HOCl) at pH levels below 7.5, and as the hypochlorite ion (OCl-) at higher pH values. HOCl is approximately 80-100x more effective as a disinfectant than OCl-, which is why water operators carefully monitor pH.

Chlorine's biggest advantage has always been its disinfection speed. At a concentration of 1.0 mg/L with a pH of 7.0 and water temperature of 20-C, free chlorine achieves a 4-log (99.99%) inactivation of E. coli in under 30 seconds. For Giardia lamblia cysts - which are far more resistant - the CT value (concentration - time) required is approximately 65-85 mg-min/L at the same conditions.

However, chlorine's reactivity is also its weakness. When free chlorine encounters natural organic matter (NOM) in source water - humic acids, fulvic acids, and other decaying plant material - it reacts to form trihalomethanes (THMs) and haloacetic acids (HAAs). The four regulated THMs are chloroform (CHCl-), bromodichloromethane (CHCl-Br), dibromochloromethane (CHClBr-), and bromoform (CHBr-). Their combined EPA Maximum Contaminant Level (MCL) is 0.080 mg/L. The five regulated HAAs (monochloroacetic, dichloroacetic, trichloroacetic, monobromoacetic, dibromoacetic) carry a combined MCL of 0.060 mg/L.

Chlorine also degrades relatively quickly in distribution systems. In warm weather, free chlorine residuals can drop from 2.0 mg/L at the treatment plant to below 0.2 mg/L at the tap within 2-3 days. This degradation can allow bacterial regrowth in dead-end water mains and storage tanks.

What Is Chloramine? The Stable Alternative

Chloramine is formed when utilities intentionally mix chlorine with ammonia (NH-) at a chlorine-to-ammonia-nitrogen ratio between 3:1 and 5:1 by weight. At this ratio, monochloramine (NH-Cl) is the dominant species. If the ratio climbs above 5:1, dichloramine (NHCl-) and trichloramine (NCl-) begin to form - both of which cause strong, objectionable tastes and odors and are less effective as disinfectants.

Monochloramine's defining characteristic is its persistence. Because it is a weaker oxidant than free chlorine (its oxidation-reduction potential is approximately 0.75V compared to 1.49V for chlorine), it reacts more slowly with organic matter and pipe walls. This means it can maintain a disinfectant residual of 0.5-2.0 mg/L throughout an entire distribution network, even in distant dead-end mains. The EPA's Surface Water Treatment Rule requires systems to maintain a detectable disinfectant residual throughout the distribution system - a requirement chloramine makes far easier to meet.

The trade-off is disinfection speed. Monochloramine's CT value for 4-log Giardia inactivation is roughly 10x higher than free chlorine - approximately 650-750 mg-min/L at pH 7.0 and 20-C. For this reason, most utilities that use chloramine practice "chloramination" - they add free chlorine first for primary disinfection (in the clearwell or contact basin), then add ammonia to convert the residual to monochloramine before the water enters the distribution system.

Utilities typically switch to chloramine to comply with the EPA's Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules (DBPR). By converting to chloramine, systems can reduce TTHM levels by 40-60% and HAA5 levels by 30-50% compared to free chlorine treatment.

Disinfection Byproducts: The Hidden Danger

The choice between chlorine and chloramine is ultimately a choice between different sets of disinfection byproducts (DBPs), many of which are carcinogenic.

Chlorine DBPs

Free chlorine reacts with natural organic matter to produce over 600 identified byproduct species. The most studied and regulated are:

• Trihalomethanes (THMs): Chloroform is a probable human carcinogen (EPA Group B2). The MCL for total THMs is 0.080 mg/L.
• Haloacetic Acids (HAAs): Dichloroacetic acid and trichloroacetic acid are both classified as probable human carcinogens. The HAA5 MCL is 0.060 mg/L.
• Haloacetonitriles (HANs): More toxic than THMs on a per-weight basis, though not currently regulated by the EPA.
• Chloral Hydrate: A CNS depressant and animal carcinogen.

Chloramine DBPs

Chloramine produces lower levels of THMs and HAAs, but generates its own concerning byproducts:

• N-Nitrosodimethylamine (NDMA): Formed when monochloramine reacts with dimethylamine-containing compounds (found in some wastewater discharges and industrial sources). NDMA is a potent carcinogen with an EPA health advisory of 0.0007 mg/L - roughly 100x lower than the TTHM MCL. The Ontario Ministry of the Environment sets a drinking water standard of 0.009 -g/L (9 ng/L).
• Iodinated disinfection byproducts: When source water contains iodide (common in brackish or coastal sources), chloramine can form iodoacetic acid and iodo-THMs. Iodoacetic acid is roughly 10x more cytotoxic and genotoxic than bromoacetic acid.
• Hydrazine: A decomposition product of monochloramine at low doses. Classified as a probable human carcinogen.
• Nitrosamines: Beyond NDMA, other N-nitrosamines including NDEA, NDPA, and NDBA have been detected in chloraminated water supplies.

A 2016 study by the Water Research Foundation found that switching from chlorine to chloramine reduced TTHMs by an average of 47% but increased NDMA formation by 340% in systems with dimethylamine precursors.

Health Effects Compared

Chlorine Health Concerns

Chlorinated drinking water has been epidemiologically associated with increased bladder cancer risk in over 20 peer-reviewed studies. A 2020 meta-analysis in Environmental Health Perspectives found a pooled relative risk of 1.27 (95% CI: 1.15-1.41) for bladder cancer among those exposed to chlorinated water for 30 years versus unchlorinated sources. The primary suspects are chloroform and bromodichloromethane.

Respiratory effects from showering in chlorinated water have also been documented. A 2007 study at the University of Pittsburgh found that inhalation exposure to chloroform during a 10-minute shower was comparable to drinking 2 liters of chlorinated tap water. Chlorine vapors can aggravate asthma - a 2019 study in Pediatric Allergy and Immunology found a 1.6x increased asthma risk in children swimming in chlorinated pools.

Chloramine Health Concerns

Chloramine exposure has been linked to skin and respiratory irritation. A 2014 survey by the U.S. EPA found that approximately 2-3% of chloramine-exposed individuals reported skin rashes, itching, or respiratory discomfort after switching to chloraminated water. Chloramine does not volatilize as readily as chlorine, so inhalation exposure during showering is lower - but skin absorption may be more significant because chloramine persists longer in warm water.

The lead leaching concern is arguably the most serious. A landmark 2004 study by Marc Edwards at Virginia Tech demonstrated that monochloramine can destabilize the protective lead dioxide (PbO-) scale that forms on lead service lines, causing lead concentrations to spike to 50-200 -g/L - well above the EPA Action Level of 15 -g/L. This mechanism contributed to the Flint water crisis (though Flint used ferric chloride, not chloramine) and has been observed in Washington D.C. (2000-2004) and other cities after disinfectant switches.

Chloramine is also toxic to kidney dialysis patients. The FDA requires that water used for hemodialysis contain zero chloramine (compared to <0.1 mg/L for chlorine). Dialysis units using chloraminated municipal water must use carbon filters specifically rated for chloramine removal and test effluent before every treatment shift.

Taste and Odor: What You'll Notice at the Tap

Chlorine produces the familiar "swimming pool" smell detectable at concentrations as low as 0.2-0.5 mg/L. Most consumers can taste free chlorine at 0.5 mg/L, and many find water above 1.0 mg/L objectionable. The good news: chlorine off-gasses readily. Fill a pitcher and let it sit for 30 minutes, and most of the chlorine will have volatilized.

Chloramine produces a sharper, more medicinal or chemical taste that many describe as "band-aid" like. Its odor threshold is higher - roughly 0.5-1.0 mg/L - but it does not dissipate with standing. Let a pitcher of chloraminated water sit overnight, and the chloramine concentration will be essentially unchanged. This is why chloramine complaints often spike after municipalities switch - the taste is harder to remove.

In taste tests conducted by the American Water Works Association Research Foundation, panelists rated chloraminated water lower in "palatability" than chlorinated water at equivalent residual concentrations. The difference was statistically significant (p<0.05) at concentrations above 1.5 mg/L.

Filtration Requirements: Why Your Filter Choice Matters

This is where the chlorine vs chloramine distinction directly impacts your wallet.

Filtering Chlorine

Standard granular activated carbon (GAC) effectively removes free chlorine through a combination of adsorption and catalytic reduction. A typical 10-inch GAC cartridge with an empty bed contact time (EBCT) of 7-10 minutes can reduce 2.0 mg/L free chlorine to <0.1 mg/L for 10,000-20,000 gallons, depending on flow rate and carbon type (bituminous coal vs. coconut shell). Under-sink carbon filters like the CuZn UC-200 and faucet-mount units like the Brita Complete are rated for chlorine reduction.

Reverse osmosis membranes reject 95-99% of free chlorine, though most RO systems include carbon pre-filters specifically to protect the TFC membrane from chlorine degradation (chlorine attacks the polyamide layer).

Filtering Chloramine

Standard GAC has minimal effect on chloramine. The catalytic reaction required to break the nitrogen-chlorine bond needs a specialized carbon surface. Catalytic activated carbon - produced through enhanced steam activation or chemical treatment - provides the reactive sites necessary. The EBCT required for effective chloramine removal is 2-3x longer than for chlorine: typically 15-20 minutes for >90% reduction.

Whole-house systems that claim chloramine reduction must use catalytic carbon and be sized accordingly. The SpringWell CF1 uses catalytic carbon and is certified to NSF/ANSI Standard 42 for chloramine reduction. Point-of-use options include multi-stage systems with dedicated catalytic carbon blocks.

KDF-85 (copper-zinc 85% formula) media can also reduce chloramine through redox reactions, though it is typically used in combination with catalytic carbon rather than as a standalone solution. KDF-55 is formulated for chlorine, not chloramine.

Reverse osmosis removes 85-95% of chloramine, but because chloramine molecules diffuse through the polyamide membrane more slowly than free chlorine, actual rejection rates vary. If chloramine levels are high (>3.0 mg/L), a dedicated catalytic carbon pre-filter is recommended even with RO.

Impact on Plumbing, Rubber, and Appliances

Free chlorine is a more aggressive oxidant and degrades rubber gaskets, O-rings, and elastomer seals faster than chloramine. Toilet flapper valves in chlorinated water may degrade in 2-3 years versus 4-5 years in chloraminated water. Similarly, washing machine hoses and dishwasher gaskets may last longer with chloramine.

However, chloramine's lead leaching risk far outweighs this benefit for homes with lead service lines or lead solder (pre-1986 construction). The EPA's Lead and Copper Rule requires utilities to monitor tap lead levels, but the sampling protocol captures only first-draw samples and may miss the episodic spikes that occur after disinfectant switches.

For aquarium owners, chloramine is significantly more dangerous than chlorine. Standard sodium thiosulfate dechlorinators neutralize free chlorine within seconds but may only partially neutralize chloramine, leaving toxic ammonia behind. Aquarium-specific conditioners that break the chloramine bond and then detoxify the resulting ammonia are essential. A 2019 survey by the Aquarium Hobbyist Association found that 23% of fish deaths in chloraminated water areas were attributed to improper dechlorination.

Which Cities Use Chlorine vs Chloramine?

The decision is made at the utility level and can change. Some major examples as of 2026:

To find your local disinfectant, check your utility's annual Consumer Confidence Report (CCR), search "[your city] water quality report 2026," or call your water department directly. Look for the terms "chloramine," "monochloramine," or "combined chlorine" in the disinfectant residual section.

Category Winners

Overall Verdict

There is no clear winner between chlorine and chloramine - and that is precisely the problem. Both are chemical disinfectants added to public water supplies to prevent waterborne disease, and both create potentially harmful byproducts. The question for homeowners is not which disinfectant is "better" but which one flows from their tap, and whether their filtration system is designed to handle it.

If your utility uses free chlorine, a standard NSF-certified activated carbon filter (point-of-use or whole-house) will effectively reduce both the disinfectant and its associated taste/odor. Options range from $25 pitcher filters to $800 whole-house GAC systems.

If your utility uses chloramine, you need a filter specifically rated for chloramine reduction - meaning catalytic carbon, not standard GAC. Budget an additional 40-60% for comparable performance. Always look for NSF/ANSI 42 certification with specific chloramine reduction claims, not just chlorine reduction.

In either case, a multi-stage approach is best: carbon for disinfectant removal plus any additional stages (sediment, KDF, RO membrane) for the specific contaminants in your water. Request your utility's Consumer Confidence Report annually, test your water if you have lead service lines or private wells, and size your filtration system to your actual water usage - not just the marketing claims on the box.

Our Methodology

Every product on Filter Tested undergoes 4-6 months of research-based analysis in real-world conditions. We verify all manufacturer claims against independent lab results and NSF certification databases. Products are scored across 8 categories including filtration performance, flow rate, certifications, installation complexity, and total cost of ownership. Learn more about how we test.

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