Chloramine is significantly harder to remove from tap water than free chlorine. You can’t boil it away quickly or let it sit in an open pitcher for a day or two. The CDC confirms that while chlorine will dissipate from water left out for a few days, chloramine will not. This stability is exactly why water utilities use it, but it means you need a deliberate removal strategy depending on your situation.
Why Chloramine Doesn’t Just Evaporate
Chloramine is formed by combining chlorine with ammonia, creating a molecule that’s smaller, more stable, and longer-lasting than free chlorine. That persistence is the whole point for water treatment: it keeps water disinfected through miles of pipes. But the same chemical stability means the off-gassing trick that works for chlorine (filling a container and letting it sit uncovered) does essentially nothing for chloramine. If your water utility uses chloramine, and most large U.S. systems do, you need an active removal method.
Catalytic Carbon Filtration
Carbon filtration is the most effective non-chemical method for removing chloramine from drinking water. But there’s an important distinction: standard activated carbon and catalytic carbon perform very differently against chloramine.
Standard activated carbon filters, the kind found in most basic pitcher filters and refrigerator cartridges, are designed primarily to improve taste and odor by removing free chlorine. They can reduce chloramine to some degree, but they work slowly and less completely. The water needs extended contact time with the carbon, which cheap pour-through filters don’t provide.
Catalytic carbon is a modified form of activated carbon with an enhanced surface that breaks chloramine down into harmless chloride. It’s considerably more effective at this specific job. If your goal is chloramine removal for drinking water, look for filters that specifically list catalytic carbon (sometimes marketed as Centaur or equivalent media) rather than plain granular activated carbon. Whole-house systems and under-sink units using catalytic carbon with adequate contact time are the gold standard for household chloramine removal.
Contact time matters with any carbon filter. The longer the water stays in contact with the carbon bed, the more complete the removal. Countertop and under-sink units with larger filter housings outperform slim pitcher-style filters for this reason. When shopping, check whether the manufacturer specifically claims chloramine reduction, not just chlorine reduction. Those are different certifications.
Vitamin C (Ascorbic Acid)
Vitamin C neutralizes chloramine through a simple chemical reaction, and it works fast. According to USDA Forest Service data, one gram of ascorbic acid neutralizes 1 milligram per liter of chlorine per 100 gallons of water. Sodium ascorbate, a buffered form of vitamin C, requires roughly 2.8 parts to neutralize 1 part chlorine.
This method is popular for filling fish tanks, treating water for homebrewing, and dechlorinating bathwater. Vitamin C shower filters use this principle, housing a cartridge of ascorbic acid that dissolves as water passes through. For smaller volumes, you can dissolve a small amount of powdered ascorbic acid directly into the water. It’s food-safe, inexpensive, and doesn’t change the water’s taste at the concentrations needed. The main limitation is that the vitamin C is consumed in the reaction, so cartridges and powder need regular replacement.
Campden Tablets (Potassium Metabisulfite)
Homebrewers have relied on Campden tablets for years because they neutralize chloramine almost instantly. The active ingredient, potassium metabisulfite, reacts with chloramine and converts it to chloride and a trace amount of sulfate, both harmless at these levels.
The dosage is small. Removing chloramine requires roughly 10 to 15 milligrams of potassium metabisulfite per liter. For a standard 5-gallon brewing batch (about 20 liters), that works out to 0.2 to 0.3 grams total, which is less than half a standard Campden tablet. You crush the tablet, stir it in, and the reaction is complete within minutes. This is one of the fastest and cheapest removal methods available, though it’s best suited for batch treatment rather than continuous household filtration.
Reverse Osmosis Systems
Reverse osmosis (RO) is often assumed to handle everything in water, but chloramine is an exception. The Water Quality Association notes that chloramines are small, stable molecules with no net charge, making them difficult to remove by RO membranes alone. A standard residential RO system without the right pre-filter will let chloramine pass through, and the chloramine can actually degrade the RO membrane over time.
Effective RO systems pair a catalytic carbon pre-filter with the membrane. The carbon stage breaks down the chloramine before the water ever reaches the membrane, protecting it and ensuring the final product is chloramine-free. If you already own an RO system, check whether your pre-filter cartridge is rated for chloramine specifically. Replacing a basic carbon pre-filter with a catalytic carbon version is a straightforward upgrade that makes the whole system work properly against chloramine.
Why UV Light Isn’t Practical
Ultraviolet light can break down chloramine, but only at doses far beyond what residential UV systems deliver. Research published in the Journal of Water Supply found that chloramine decay at typical UV disinfection doses (under 100 millijoules per square centimeter) was negligible. Researchers had to push UV doses up to 1,500 millijoules per square centimeter to demonstrate meaningful breakdown, roughly 10 to 100 times higher than what standard home UV units produce. UV purifiers are excellent for killing bacteria and viruses, but they won’t make a noticeable dent in chloramine levels.
Choosing the Right Method
Your best option depends on how much water you need to treat and why you’re removing chloramine in the first place.
- Whole-house drinking water: A catalytic carbon filter installed at the point of entry handles every tap. These systems use larger carbon beds with sufficient contact time for thorough removal.
- Kitchen sink only: An under-sink catalytic carbon filter or an RO system with a catalytic carbon pre-stage covers cooking and drinking water without the cost of a whole-house setup.
- Fish tanks and aquariums: Chloramine is toxic to fish at any concentration. Vitamin C or a dedicated aquarium dechlorinator works for water changes. Treat the water before adding it to the tank, not after.
- Homebrewing: Campden tablets are the go-to. A fraction of a tablet treats a full batch in minutes, costs pennies, and leaves no flavor impact at proper dosing.
- Bathwater or shower: Vitamin C shower filters are the most accessible option. They won’t last as long as carbon systems, but they’re easy to install and replace.
One thing to verify before investing in any system: confirm your water utility actually uses chloramine rather than free chlorine. Your annual water quality report (sometimes called a Consumer Confidence Report) will list the disinfectant type. If your utility uses free chlorine only, simpler and cheaper removal methods will work fine. Chloramine requires the more targeted approaches described above.