If you've ever noticed a different smell or taste in your tap water, or wondered why your utility sent a notice about changing disinfectants, you're not alone. Over the past two decades, thousands of water utilities across the United States have made a significant shift: from using chlorine to disinfect drinking water to using chloramine instead. This change affects roughly 100 million Americans today.
While both are disinfectants approved by the EPA, they work differently, carry different health considerations, and have real practical implications for certain uses like aquariums and dialysis. Understanding which one your utility uses and what it means for your household is easier than you might think. This article breaks down the science, explains why utilities made the switch, and helps you figure out what steps to take.
What Are Chlorine and Chloramine?
Chlorine and chloramine are both disinfectants used to kill harmful bacteria, viruses, and other microorganisms that can cause waterborne illness. They are not contaminants; they are intentionally added by water utilities as a safety measure.
Chlorine is a gas that dissolves in water and immediately begins killing pathogens. It is one of the oldest and most widely used water disinfectants in the world, dating back to the early 1900s. Chlorine works fast and effectively but also dissipates relatively quickly from water as it travels through pipes.
Chloramine is created by combining chlorine with ammonia. The resulting compound is weaker than free chlorine but much more stable and longer-lasting. Because it persists in water as it moves through the entire distribution system, chloramine provides what water professionals call a "residual disinfectant" effect all the way to your tap.
Why Did Water Utilities Switch from Chlorine to Chloramine?
The shift to chloramine was not random or sudden. It was driven by specific EPA regulations and public health concerns that emerged in the 1980s and 1990s.
The Disinfection Byproducts Problem
When chlorine reacts with naturally occurring organic matter in water (like decaying leaves, algae, and other organic compounds), it creates byproducts called disinfection byproducts (DBPs). The most common and heavily regulated DBPs are trihalomethanes, or TTHMs. These include chloroform, bromodichloromethane, dibromochloromethane, and bromoform.
In 1979, the EPA discovered that TTHMs could pose health risks, including links to cancer in animal studies. This led to the Phase 1 Rule in 1979 and later the Phase IIb Rule in 1992, which set strict limits on TTHM levels in drinking water. The current EPA Maximum Contaminant Level (MCL) for TTHMs is 80 parts per billion (ppb), and for haloacetic acids (another group of DBPs) is 60 ppb.
Here's where chloramine enters the story: when chloramine is used as the primary disinfectant, it produces far fewer TTHMs than chlorine does. This made it an attractive option for utilities struggling to meet EPA regulations. Many utilities that could not reduce TTHM levels with chlorine alone switched to chloramine as a compliance strategy.
Better Residual Protection
Chloramine also offers a practical advantage: it persists in water much longer than chlorine. Because water must travel long distances through pipes before reaching homes, especially in large cities, maintaining a disinfectant residual throughout the entire distribution system is crucial. If a break in the main occurs, or if water sits in pipes for extended periods, bacteria can regrow. Chloramine's stability makes it better suited to large distribution systems.
The Trade-Off: Different Byproducts, New Health Questions
The switch to chloramine was not a perfect solution. It solved one DBP problem but created another.
Chloramine and Iodoacetic Acid
While chloramine produces fewer TTHMs, it produces significantly more iodoacetic acid (IAA) and other oxygenated DBPs when the source water contains high levels of iodine. Iodoacetic acid is a regulated DBP in some countries but, notably, the EPA has not yet set a Maximum Contaminant Level for it in the United States. This regulatory gap means some utilities do not routinely monitor for IAA.
Studies have raised questions about potential mutagenic effects of IAA, though long-term epidemiological data on human health effects remain limited compared to our understanding of TTHMs. This uncertainty is why some water quality advocates view chloramine as a "trade-off" rather than a straight upgrade.
Other Health Considerations
Chloramine is generally considered safe at the levels used in drinking water treatment. The EPA and CDC both affirm that both chlorine and chloramine disinfectants are safe when used properly. However, people with specific medical conditions or activities need to know about chloramine's presence for practical reasons (discussed below).
Practical Implications: When Chloramine Matters Outside Your Glass
For most people drinking tap water, the choice between chlorine and chloramine has little impact on health. But there are specific situations where knowing which disinfectant your utility uses becomes very important.
Aquariums and Fish Tanks
Both chlorine and chloramine are toxic to fish and aquatic plants. However, chlorine can be removed by letting water sit in an open container for 24-48 hours, as it is volatile and escapes into the air. Chloramine cannot be removed this way because it is much more stable. It requires either:
- Activated carbon filtration
- Reverse osmosis
- Specific dechloramine products designed for aquariums
If you have an aquarium and your utility uses chloramine, you must treat your water before adding it to the tank or your fish will die. This is one of the most common practical impacts homeowners encounter.
Kidney Dialysis
Patients undergoing home hemodialysis or peritoneal dialysis require very high-quality water. Chloramine can interfere with dialysis machines and affect the treatment process. Dialysis centers and home dialysis patients are required to use specialized water treatment systems that remove both chlorine and chloramine. If you or a family member relies on home dialysis, your water supplier should already have informed you of any switch to chloramine, but it's worth verifying.
Wound Care and Medical Uses
In some clinical settings, water used for wound irrigation or certain medical procedures must be chloramine-free. Healthcare providers are aware of this requirement, but patients using home medical equipment should confirm with their provider whether they need special water treatment.
How to Find Out Which Disinfectant Your Water Utility Uses
There are several straightforward ways to learn whether your utility uses chlorine, chloramine, or both.
Check Your Water Quality Report
Every public water system is required by the EPA to produce an annual Water Quality Report (also called a Consumer Confidence Report). This report must disclose what disinfectants are used, at what levels, and the results of any tests performed. You can find your utility's report by:
- Visiting your water utility's official website
- Searching the utility's name plus "water quality report" or "consumer confidence report"
- Calling your utility directly and requesting the report
The report will typically state something like "Primary disinfectant: chloramines" or "Primary disinfectant: free chlorine." Many utilities now publish these online as PDFs or interactive dashboards.
Use ClearWater's Free Lookup Tool
If you want a faster way to understand your local water quality, including disinfectant type, ClearWater offers a free EPA drinking water quality lookup tool. Simply enter your ZIP code at checkclearwater.com, and you'll get a detailed breakdown of what's in your tap water, including which disinfectant your utility uses and current levels of key contaminants and byproducts. No signup required, no cost.
Ask Your Utility Directly
If you can't find the information online, call your local water utility's customer service line. Ask: "What disinfectant do you use to treat drinking water, and have there been any recent changes?" Most utilities are happy to answer this question and can also tell you if you fall within the service area if you're unsure.
Should You Filter Out Chloramine or Chlorine?
This depends on your specific situation and concerns.
For Taste and Odor
Both chlorine and chloramine can give water a noticeable taste and smell. Chlorine often smells more like a swimming pool, while chloramine has a slightly different but equally noticeable odor. If this bothers you, filtration can help.
- Chlorine removal: Activated carbon filters (pitcher filters, under-sink systems, or whole-house systems) remove chlorine very effectively. A simple pitcher filter with activated carbon will eliminate most of the taste and odor.
- Chloramine removal: Chloramine is harder to remove and requires larger amounts of activated carbon or longer contact time. Many pitcher filters are not sufficient; reverse osmosis or whole-house carbon systems are more effective.
For Health Protection
If you're concerned about DBP exposure, the answer is more nuanced. Chlorination byproducts exist in the water before it reaches your home. However, an additional concern is that chloramine and chlorine can form new byproducts as they react with organic matter in your plumbing as water sits in your pipes at home.
Standard activated carbon filters reduce some DBPs but not all. Reverse osmosis systems remove a broader range of contaminants, including disinfection byproducts, but they also remove beneficial minerals and waste water in the process.
Before investing in a filtration system, use ClearWater to check your actual water quality data. If your utility's TTHM or HAA levels are already below EPA limits (which they should be), the health benefit of additional home filtration is debatable. However, if you're in an area with a known water quality issue or you simply want the greatest level of protection, filtration is a reasonable choice.
For Specific Uses
As mentioned above, if you have an aquarium or medical equipment, filtration of chloramine is not optional. Activated carbon or reverse osmosis is necessary.
What Does the Science Say About Chloramine Safety?
The EPA, CDC, and World Health Organization all consider chloramine a safe drinking water disinfectant when used within regulatory limits. The current MCL for chlorine residual is 4 mg/L, and the residual disinfectant level (including chloramine) must be between 0.2 and 4 mg/L.
Studies on the long-term health effects of chlorinated and chloraminated drinking water show mixed results. Some older research suggested possible links between long-term TTHM exposure and certain cancers, but newer epidemiological studies have not found strong causal evidence. The EPA regularly reviews this research and updates regulations as needed.
The key takeaway: both chlorine and chloramine have passed rigorous regulatory review, and the levels used in US drinking water are considered safe. The switch to chloramine was driven by regulatory compliance on TTHMs, not by any proven safety problem with chlorine itself.
Key Takeaways: What You Should Do Now
- Find out which disinfectant your utility uses. Check your annual water quality report, use ClearWater's free lookup tool, or call your utility. It takes five minutes and answers an important question about your water.
- If you have an aquarium or medical equipment, confirm water treatment needs. If your utility uses chloramine, you cannot simply let tap water sit overnight. You'll need appropriate filtration or treatment products.
- Evaluate filtration based on your actual water quality data. Don't filter "just in case." Use your utility's published test results and ClearWater to understand what's actually in your water, then make an informed decision.
- Remember that both disinfectants are regulated and safe. The presence of chlorine or chloramine in your tap water is a feature, not a bug. Both are essential to preventing waterborne disease.
- Stay informed about changes. If your utility switches disinfectants, they should notify you. Pay attention to these notices, especially if you have fish tanks, medical equipment, or other special water needs.
The Bottom Line
The shift from chlorine to chloramine across American water systems reflects the EPA's effort to balance multiple public health priorities: preventing microbial contamination while limiting disinfection byproducts. Neither choice is perfect, but both are safe and effective when properly managed.
For the vast majority of people, drinking chloraminated or chlorinated tap water poses no health risk. The main differences you'll notice are taste, odor, and practical considerations like aquarium maintenance. By knowing which disinfectant your utility uses and understanding what it means for your specific situation, you can make informed decisions about filtration, water use, and whether any additional steps are necessary for your household.
Start by checking your water quality report or using a free tool like ClearWater to see exactly what's in your tap water. It's the first step toward confident, informed water consumption.