Chloramine is a drinking-water disinfectant used by many public water systems, usually as a longer-lasting secondary disinfectant after primary treatment.
It is most commonly formed when ammonia is added to chlorine under controlled treatment conditions. Compared with free chlorine, monochloramine generally persists longer as treated water moves through distribution pipes.
Quick answer: Chloramine is more persistent than free chlorine. If you want to reduce it at home, letting water stand is generally not an effective approach. Choose a treatment method with documented chloramine-reduction performance for the exact filter or media being used.
Last reviewed: October 19, 2026. Educational information, not medical advice.
What Is Chloramine?
Chloramines are formed when ammonia is added to chlorine during drinking-water treatment. Several chloramine compounds can exist, but monochloramine is the form most commonly used for public drinking-water disinfection.
Its stability makes it useful as a secondary disinfectant because it can maintain a residual farther into a distribution network than free chlorine.
Why Do Water Utilities Use Chloramine?
Many public water systems use chlorine during treatment, but utilities also need to maintain water quality after treated water enters storage tanks and distribution pipes. Chloramine can provide a longer-lasting residual and may be used as part of a strategy to manage certain disinfection byproducts.
Not every utility uses chloramine. Treatment choices depend on source-water chemistry, infrastructure, regulatory requirements, distribution conditions, and treatment goals.
Chloramine vs. Chlorine: What's the Difference?
| Characteristic | Free Chlorine | Chloramine |
|---|---|---|
| Reaction speed | Acts relatively quickly | Generally reacts more slowly |
| Persistence | Dissipates more readily | Persists longer in distribution |
| Taste and odor | Can have a noticeable chlorine taste or smell | May be less noticeable to some people; sensitivity varies |
| Standing/aeration | Can dissipate more readily | Does not dissipate nearly as easily |
| Carbon filtration | Generally easier to reduce | Requires chloramine-specific performance and adequate contact time |
If your utility uses free chlorine instead, see our Chlorine in Drinking Water Guide.
What Does EPA Say About Chloramine?
Chloramine is intentionally used for drinking-water disinfection. EPA's federal Maximum Residual Disinfectant Level (MRDL) for chloramines is 4.0 mg/L as Cl₂.
The phrase “as Cl₂” means the result is expressed as chlorine equivalent, the reporting basis used for disinfectant residuals. At drinking-water concentrations, 4.0 mg/L is approximately 4 ppm. This is an MRDL for a disinfectant, not the separate MCL for a disinfection byproduct.
EPA says chloraminated water meeting regulatory standards is suitable for drinking, cooking, and bathing. Public systems monitor residuals under prescribed rules; a home test alone does not establish regulatory compliance. Contact the utility about an unexpectedly high reading or a notice.
Can You Remove Chloramine by Letting Water Sit or Boiling It?
Leaving water in an open container is not an effective general approach to chloramine because chloramine is substantially more stable than free chlorine.
Ordinary boiling is not a dependable household chloramine-reduction method. Choose treatment with documented performance instead. If your utility issues a boil-water advisory for a microbial problem, follow that advisory; microbial safety and disinfectant reduction are separate issues.
How Can You Tell If Your Water Contains Chloramine?
Start with your public water system's annual Consumer Confidence Report (CCR) or contact the utility directly. Ask whether the system uses free chlorine, chloramine, or seasonal switching between disinfectants.
Ask whether the CCR’s chlorine entry represents free or total chlorine. A total-chlorine result does not mean that the utility uses free chlorine alone, and a CCR is not a measurement of your tap today.
Free chlorine, total chlorine and combined chlorine
With an appropriate test method, total chlorine minus free chlorine estimates combined chlorine, which includes chloramines. For example, 2.0 mg/L total and 0.1 mg/L free gives approximately 1.9 mg/L combined chlorine, all on the same “as Cl₂” basis. This screening calculation does not identify monochloramine specifically.
Use a drinking-water test kit suited to the expected range, follow its reagent timing, and measure promptly at collection. Residuals can change during storage. For precise confirmation, ask the utility or a qualified laboratory about an appropriate method. A TDS meter or taste or odor cannot establish chloramine concentration.
To assess a filter, compare source and filtered water using the same suitable method and record the filter’s age and treated volume. Repeat checks as it ages. “Not detected” means below the method’s limit, not necessarily zero.
Situations Where Chloramine Requires Extra Attention
Aquariums
Chlorine and chloramine must be removed or neutralized appropriately before municipal water is used for fish. Use aquarium-specific treatment that addresses chloramine and any ammonia left by treatment, following aquarium guidance. Do not use aquarium conditioners in drinking water.
Home Dialysis
Dialysis water requires specialized treatment and monitoring. Anyone receiving dialysis at home should follow the requirements set by the healthcare team and the equipment manufacturer rather than relying on ordinary household drinking water filtration.
How Can Chloramine Be Reduced at Home?
Activated Carbon
Carbon filtration can reduce chloramine, but performance varies with media type, media quantity, flow rate, contact time, source-water conditions, and filter condition. A generic chlorine claim should not automatically be treated as a chloramine claim.
Catalytic Carbon
Catalytic activated carbon is commonly used when chloramine reduction is a specific treatment goal because it can improve the reactions involved in chloramine decomposition.
Reverse Osmosis Systems
Reverse-osmosis systems commonly include carbon pretreatment. When chloramine is present, the pretreatment stages are important; the membrane itself should not be viewed as the only relevant step in chloramine treatment.
Look for chloramine-specific evidence. Do not assume that every carbon filter provides the same level of chloramine reduction. Review performance information for the exact product and follow its replacement guidance.
Look for a specific certified claim
Chloramine reduction is a distinct claim under NSF/ANSI 42. Verify the exact model, replacement element, rated capacity, and flow. A chlorine-only claim or a general NSF logo does not establish chloramine reduction.
Choose where you need treatment
A countertop or under-sink system treats drinking and cooking water at that point. It does not treat shower or bath water. A whole-house system needs sizing for peak flow, documented chloramine performance, and regular maintenance. Removing the disinfectant before household plumbing makes system hygiene especially important.
After filtration, keep reservoirs and containers clean and follow storage instructions. Removing chloramine does not disinfect contaminated water or demonstrate removal of already-formed byproducts.
Black Berkey® and Phoenix Gravity Chloramine Evidence
Both Black Berkey® Elements and Phoenix Gravity New Millennium Edition™ elements have independent laboratory evidence for chloramine reduction. The evidence belongs to the named element and test conditions, not the stainless-steel vessel.
Black Berkey® Elements
Envirotek report 14-260, dated October 15, 2014, lists chloramines at 3.2 mg/L before filtration and below 0.1 mg/L afterward. Those displayed concentrations support greater than 96.87% reduction, rounded downward conservatively. The printed 99.9% figure cannot be established from the displayed reporting limit, so we use the calculated lower bound.
Phoenix Gravity New Millennium Edition™
The April 20, 2026 Atom report lists 3.02 mg/L before filtration and below 0.1 mg/L afterward, supporting greater than 96.68% reduction, rounded downward conservatively. The complete report is linked from our test-results reference.
These reports support chloramine reduction under the documented laboratory conditions. They are not a side-by-side comparison, a guarantee for every water supply or proof of chloramine performance through the full advertised service life. A result below 0.1 mg/L is not proof of zero residual.
Testing and certification are different. As checked on October 19, 2026, the NSF listing for Phoenix-equipped Travel, Big and Royal Berkey systems identifies chlorine and taste-and-odor reduction under NSF/ANSI 42, not chloramine reduction. The chloramine findings discussed here are laboratory evidence, not chloramine-certification claims for either element.
Review the reports for both Black Berkey and Phoenix Gravity, then use the replacement filters page for availability and compatibility.
Chloramine and Disinfection Byproducts
One reason utilities may use chloramination is to help manage formation of certain regulated disinfection byproducts associated with free chlorine. Chloramination does not eliminate disinfection-byproduct considerations; utilities still balance disinfectant effectiveness, source-water chemistry, distribution conditions, and regulated byproduct formation.
What If Your Tap Water Suddenly Tastes Different?
A change in taste or odor does not automatically mean the water is unsafe or that chloramine has suddenly appeared. Seasonal changes in source water, treatment adjustments, water temperature, and building plumbing can all affect taste.
If the change is strong, sudden, persistent, or accompanied by unusual color or sediment, contact your water utility rather than diagnosing the issue from taste alone.
Frequently Asked Questions
Does every city use chloramine?
No. Some utilities use free chlorine, some use chloramine, and some may change treatment approaches depending on operating conditions.
Is chloramine the same as chlorine?
No. Monochloramine is commonly formed by adding ammonia to chlorine under controlled treatment conditions. It is generally more persistent than free chlorine.
Can I remove chloramine by leaving water out overnight?
Not effectively in the way this method is sometimes used for free chlorine. Chloramine is considerably more stable.
Does activated carbon reduce chloramine?
Some carbon systems can reduce chloramine, but performance varies with media, contact time, flow rate, source-water conditions, and filter condition. Look for chloramine-specific data.
How can I find out whether my water contains chloramine?
Check your public water system's Consumer Confidence Report or contact the utility directly.
Do Phoenix Gravity filters reduce chloramine?
Independent April 2026 laboratory testing reported chloramine at 3.02 mg/L before filtration and below 0.1 mg/L after filtration, supporting a conservative reduction greater than 96.68% under the documented test conditions. This is separate from the current NSF/ANSI 42 Berkey® listings, which identify chlorine reduction and taste-and-odor reduction rather than chloramine reduction.
When should a chloramine filter be replaced?
Follow the rated-capacity or replacement guidance for the exact filter. Do not assume chloramine performance continues indefinitely beyond the product's intended service life.
Do Black Berkey® Elements reduce chloramine?
Yes. The Envirotek report discussed above includes chloramine testing for Black Berkey® Elements. Its displayed concentrations support reduction greater than 96.87% under the reported conditions. Read the original report and its limitations; do not substitute Phoenix results for Black Berkey evidence.
Does a chlorine certification also cover chloramine?
No. Verify that chloramine reduction is explicitly listed for the exact model and replacement element. Chlorine and chloramine are separate performance claims.
Practical Next Steps
- Confirm the current disinfectant with your utility, including seasonal switches.
- Decide whether your goal is drinking-water taste, verified chloramine reduction, or another specific concern.
- Choose evidence for that exact claim, follow replacement guidance, and keep the system clean.