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Last updated: April 2026 | Reading time: ~9 minutes
You installed a carbon filter to get rid of the chlorine taste in your tap water. A month later, the taste is still there. The filter isn’t broken — your utility may be using chloramine instead of chlorine, and standard activated carbon doesn’t reduce chloramine effectively. It’s one of the most common and most expensive filter mistakes homeowners make.
Chlorine and chloramine are both EPA-approved disinfectants, but they behave differently in your water, react differently with filter media, and require different treatment approaches. This guide covers what each one is, how to find out which your utility uses, and what it means for choosing the right filter.
Quick Answer
Chlorine (Cl₂) is a standalone disinfectant that dissipates relatively quickly and is reduced effectively by standard activated carbon. Chloramine (NH₂Cl) is a compound of chlorine and ammonia that persists longer in the distribution system and requires catalytic carbon or extended contact time for effective reduction. Your utility’s annual water quality report (CCR) or website will confirm which disinfectant your water system uses. If your water contains chloramine, you need a filter specifically designed or certified for chloramine reduction — a standard carbon filter certified only for chlorine (NSF/ANSI 42) may not be sufficient. See our comparison of NSF 42 vs NSF 53 for more on what each standard covers.
What Chlorine Does in Your Water
Chlorine has been used as a primary drinking water disinfectant in the United States since the early 1900s. Municipal water utilities add chlorine to water at the treatment plant to inactivate bacteria, viruses, and other microorganisms before the water enters the distribution system.
Chlorine is reactive. It works quickly but also breaks down relatively quickly as it travels through the pipe network and reacts with organic matter in the water. By the time water reaches your tap, the residual chlorine concentration is typically between 0.2 and 4.0 mg/L (ppm), which is within the EPA’s maximum residual disinfectant level (MRDL) of 4.0 mg/L.
Because chlorine dissipates, it can also be reduced from tap water through simple methods: letting water sit uncovered for 24–48 hours allows chlorine to off-gas, and standard activated carbon filters reduce chlorine effectively through adsorption.
What Chloramine Is (and Why Utilities Use It)
Chloramine is formed by combining chlorine with ammonia (NH₃). The result is a more stable disinfectant compound — monochloramine (NH₂Cl) — that persists much longer in the distribution system than free chlorine. This persistence is the reason utilities use it: chloramine maintains disinfectant residual across long pipe networks where chlorine would have dissipated before reaching the end of the line.
The EPA’s maximum residual disinfectant level for chloramine is also 4.0 mg/L, the same as chlorine. As of EPA data, approximately 1 in 5 Americans receives water treated with chloramine rather than chlorine, and the number of utilities switching from chlorine to chloramine has increased over the past two decades.
Important Distinction: Both chlorine and chloramine are EPA-approved disinfectants that meet federal drinking water regulations. The difference between them is a water treatment and filter selection consideration, not a safety distinction. This is a factual/regulatory distinction, not a health claim.
Chlorine vs Chloramine: Side-by-Side
| Characteristic | Chlorine (Cl₂) | Chloramine (NH₂Cl) |
|---|---|---|
| Chemical composition | Free chlorine | Chlorine + ammonia compound |
| Persistence in distribution | Dissipates relatively quickly | Remains stable much longer |
| EPA MRDL | 4.0 mg/L | 4.0 mg/L |
| Taste and odor | Noticeable chlorine smell; can off-gas if water sits | Milder taste/odor; does not off-gas readily |
| Off-gassing | Yes — dissipates if water sits uncovered 24–48 hours | No — remains stable; does not evaporate from standing water |
| Standard carbon filter effectiveness | Effective — standard activated carbon reduces chlorine readily | Limited — standard carbon alone does not effectively reduce chloramine |
| Filter requirement | Standard GAC or carbon block (NSF/ANSI 42) | Catalytic carbon or extended contact time carbon (verify chloramine-specific certification) |
| Aquarium and fish safety | Must be dechlorinated before use | Must be specifically treated; standard dechlorinators may not be sufficient |
How to Find Out Which Your Utility Uses
You need to know whether your water is treated with chlorine or chloramine before choosing a filter. Three ways to find out:
Check your Consumer Confidence Report (CCR). Every municipal water utility serving more than 15 connections is required by the EPA to publish an annual CCR. The report lists which disinfectant is used and the residual levels detected. Find your CCR through the EPA’s search tool at epa.gov/ccr or on your utility’s website.
Visit your utility’s website. Many utilities state their disinfection method directly on their water quality or FAQ page. Look for language like “we use chloramine as our secondary disinfectant” or “our system switched from chlorine to chloramine in [year].”
Call your utility directly. If you can’t find the information online, call your water utility’s customer service line and ask: “Does our water system use free chlorine or chloramine for disinfection?” This is public information they are required to provide.
Key Point: Some utilities use chlorine as the primary disinfectant at the treatment plant and chloramine as the secondary disinfectant in the distribution system. In this case, the water arriving at your tap contains chloramine. What matters for filter selection is what’s in your water at the point of use, not what was added at the plant.
Why This Matters for Filter Selection
This is where the chlorine vs chloramine distinction has a direct cost impact. Standard activated carbon (GAC and basic carbon block) reduces free chlorine effectively through a straightforward adsorption reaction. Chloramine, however, is a more stable compound that does not break down through the same adsorption process at the same rate.
Chlorine Reduction
Standard activated carbon filters certified to NSF/ANSI 42 for chlorine taste and odor reduction are sufficient. See our guide to how water filters work for a full explanation of carbon filtration. The carbon adsorbs free chlorine on contact. GAC and carbon block filters both handle chlorine effectively, with carbon block providing more consistent contact time.
Chloramine Reduction
Chloramine requires one of the following approaches:
Catalytic carbon. This is activated carbon that has been specially treated (typically through a high-temperature process) to enhance its ability to break down chloramine. Catalytic carbon converts chloramine into harmless chloride and ammonia gas through a catalytic reaction on the carbon surface, rather than relying on standard adsorption alone.
Extended contact time. Some carbon block filters can reduce chloramine if the water has sufficient contact time with the carbon media. This typically means slower flow rates and/or larger carbon blocks. The key variable is the ratio of carbon volume to flow rate.
| Your Disinfectant | Carbon Type Needed | What to Verify |
|---|---|---|
| Chlorine | Standard activated carbon (GAC or carbon block) | NSF/ANSI 42 certification for chlorine taste and odor reduction |
| Chloramine | Catalytic carbon or extended-contact carbon block | Certification specifically listing chloramine reduction; verify at NSF’s product database |
Key Limitation: A filter certified to NSF/ANSI 42 for “chlorine taste and odor” reduction is not automatically effective for chloramine. These are different compounds requiring different treatment mechanisms. Always check the product’s certification page to see whether chloramine is specifically listed as a reduced contaminant. If the certification only says “chlorine,” assume it does not cover chloramine. Learn how to verify a product’s specific certifications in our NSF certification guide.
Frequently Asked Questions
Does my water have chlorine or chloramine?
Check your utility’s Consumer Confidence Report (CCR) or call your utility directly. Your CCR is available through the EPA’s search tool at epa.gov/ccr. The report will specify whether your system uses free chlorine, chloramine, or both. You can also purchase test strips that distinguish between free chlorine and total chlorine (which includes chloramine) — if total chlorine is significantly higher than free chlorine, your water likely contains chloramine.
Can I just let chloramine evaporate like chlorine?
No. Chloramine is far more stable than free chlorine and does not off-gas from standing water. Leaving chloraminated water uncovered for days will not meaningfully reduce the chloramine concentration. This stability is the reason utilities use it — and the reason it requires a different filtration approach than chlorine.
Will a Brita filter remove chloramine?
Standard pitcher filters use granular activated carbon, which is designed to reduce free chlorine (NSF/ANSI 42). Most standard pitcher filters are not certified for chloramine reduction. Some newer pitcher models use enhanced carbon media designed for chloramine — check the specific product’s certification listing at NSF’s product database to confirm whether chloramine is listed. The correct term is “reduce,” not “remove.”
Does reverse osmosis reduce chloramine?
RO systems include carbon pre-filters that do most of the chloramine reduction work before water reaches the membrane. In fact, the carbon pre-filter is essential — chloramine can damage RO membranes. A properly designed RO system with catalytic carbon pre-filtration will reduce chloramine effectively. However, the RO membrane itself (NSF/ANSI 58) is certified for dissolved solids reduction, not chloramine specifically. The chloramine reduction happens at the carbon stage.
Why are more utilities switching to chloramine?
Chloramine produces fewer disinfection byproducts (DBPs) — specifically trihalomethanes (THMs) and haloacetic acids (HAAs) — than free chlorine when it reacts with organic matter in water. The EPA regulates DBP levels under the Stage 2 Disinfectants and Disinfection Byproducts Rule. Utilities that have difficulty meeting DBP limits with free chlorine often switch to chloramine as a compliance strategy. This is a regulatory and operational decision made by the utility.
What to Do Next
Knowing which disinfectant your water contains is the first step toward choosing the right filter. Here’s what to do with that information:
Confirm your disinfectant. Check your utility’s website or your annual water quality report (CCR) to verify whether your water is treated with chlorine or chloramine. Find your CCR at epa.gov/ccr.
If your water uses chlorine: A standard activated carbon filter certified to NSF/ANSI 42 for chlorine taste and odor reduction will address residual chlorine. This is the most common and least expensive filtration scenario.
If your water uses chloramine: Look for filters with catalytic carbon or that specifically list chloramine reduction in their NSF certification. Verify the product’s certification at NSF’s product database (info.nsf.org/Certified/DWTU/) and confirm chloramine is listed, not just chlorine.
Check your filter if you already have one. If you have an existing filter and your water uses chloramine, review the product’s certification. If it’s certified only for chlorine reduction, it may not be effectively reducing the chloramine in your water — even if it appears to be working.
Sources & Standards Referenced
NSF/ANSI 42 – Drinking Water Treatment Units – Aesthetic Effects | nsf.org
NSF/ANSI 58 – Reverse Osmosis Drinking Water Treatment Systems | nsf.org
NSF Product and Service Listings – Drinking Water Treatment Units | info.nsf.org/Certified/DWTU/
EPA – Consumer Confidence Reports | epa.gov/ccr
EPA – Stage 2 Disinfectants and Disinfection Byproducts Rule | epa.gov/dwreginfo/stage-1-and-stage-2-disinfectants-and-disinfection-byproducts-rules
EPA – Drinking Water Standards and Regulations | epa.gov/dwstandardsregulations