Chloramine vs chlorine: which is in your tap water and why it matters

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Short answerCheck your utility's annual Consumer Confidence Report. If it lists chloramine or chloramines as the disinfectant, an ordinary carbon filter will not keep up: you need catalytic carbon with about 3 minutes of contact time. If it lists only chlorine, standard activated carbon handles it, and a pitcher or under-sink filter may be all you need.

Your utility’s annual water quality report, the Consumer Confidence Report, tells you which disinfectant it uses. If it says chlorine, any decent activated carbon filter removes it. If it says chloramine, you need catalytic carbon and more contact time, because chloramine is built to last and ordinary carbon struggles with it.

Both are safe to drink at the levels utilities use. The difference matters for which filter works, and for three groups in particular: people on home dialysis, fish keepers, and anyone buying a whole-house filter.

What each one is

Chlorine is the classic disinfectant. Chloramines form when a utility adds ammonia to chlorine; the common form in drinking water is monochloramine. EPA says chloramines have been used since the 1930s, and more than one in five Americans now drinks chloraminated water.

The CDC summarizes the trade-off:

EPA says the most typical purpose of chloramine is to protect water quality as it moves through the pipes, and the CDC notes it forms fewer disinfection byproducts than chlorine.

How to find out which one your utility uses

1. Read your Consumer Confidence Report. EPA requires community water systems to send one by July 1 every year. Search your utility’s website for “water quality report” and look in the disinfectant section for “chlorine” or “chloramine.” You can also use EPA’s CCR search tool or call the utility and ask.
2. Test it yourself. A DPD test kit measures free chlorine and total chlorine. Total minus free is combined chlorine, the chloramine fraction. If most of the total is combined, your utility uses chloramine.
3. On a private well, you have neither unless you chlorinate the water yourself.

While you are on the report, check PFAS and other results too; our PFAS lookup pulls the federal data by ZIP code.

Why chloramine needs a different filter

Carbon removes free chlorine quickly, in a minute or two of contact. Chloramine reacts far more slowly. Robert Potwora’s analysis in Water Conditioning & Purification found monochloramine needs at least two to four times the contact time of free chlorine, and recommends at least 10 minutes of empty bed contact time (EBCT) with ordinary granular carbon. Catalytic (surface-enhanced) carbon cuts that to about 3 minutes.

That is the whole story in one number. US Water Systems’ Matrixx tanks, for example, give water about a minute of contact at full rated flow. That is enough for chlorine and far too little for chloramine unless the carbon is catalytic.

Checking contact time

EBCT in minutes equals the cubic feet of media times 7.48, divided by the flow in gallons per minute. For example, US Water Systems’ 10 gpm Matrixx catalytic carbon tank holds 1.5 cubic feet:

• At its full 10 gpm rating: 1.5 × 7.48 ÷ 10 = 1.1 minutes.
• At one 2.5 gpm shower: 1.5 × 7.48 ÷ 2.5 = 4.5 minutes.

Most of the day your flow is closer to the second number, which gives catalytic carbon the 3 or more minutes it needs. If you want margin during peak use, choose one size up. Our sizing guide walks through the math for every size.

What the certification says

The relevant standard is NSF/ANSI 42, which has a separate claim for chloramine. To earn it, a filter must reduce a 3.0 mg/L monochloramine challenge to below 0.5 mg/L across its rated capacity. A chlorine claim under the same standard says nothing about chloramine, so check which one a product actually lists.

None of the whole-house chloramine filters we track holds an NSF/ANSI 42 certification for chloramine. Aquasana’s Rhino Chloramines is “tested to” NSF/ANSI 42 by the maker, not certified. SpringWell’s CF1 uses catalytic carbon and claims chloramine removal without a certification, though its warranty includes a performance guarantee that the carbon keeps chlorine and chloramine below detection for 6 years or 1 million gallons.

Dialysis

EPA says dialysis patients can safely drink chlorinated or chloraminated water. The problem is dialysis machines: chlorine and chloramine must be removed from dialysis water because it contacts the blood directly.

Pennsylvania’s environmental agency says dialysis centers and hospitals are notified before a water system converts to chloramine, and technicians verify the residual is fully removed. If you do home dialysis, confirm with your care team that your water treatment is set up for chloramine, especially if your utility has recently switched.

Aquariums and ponds

Both disinfectants are toxic to fish because they pass straight into the bloodstream through the gills, and EPA notes they also inhibit the beneficial bacteria a tank depends on. Aging water in a bucket works for chlorine but not for chloramine.

Use a conditioner labeled for chloramine. Fritz Aquatics explains the catch with basic dechlorinators: they break the chlorine-ammonia bond and neutralize the chlorine, “but the ammonia is left behind, free in the water.” A chloramine-rated conditioner handles both. Pennsylvania’s guidance also suggests pet-store test kits or carbon filtration for ponds.

Other effects around the house

• Rubber parts. Pennsylvania’s environmental agency says chloramine deteriorates natural rubber, such as toilet flapper valves, faster than chlorine. Synthetic replacements are sold at hardware stores.
• Taste and odor. Pennsylvania’s environmental agency says chloraminated systems often get fewer taste and odor complaints than chlorinated ones.
• Other pets. The CDC says dogs, cats and birds are not affected at utility levels.

You may not need a whole-house filter

If your only complaint is taste at the kitchen tap, a pitcher, faucet or under-sink filter certified to NSF/ANSI 42 for chloramine costs far less than any whole-house system. Whole-house catalytic carbon makes sense if you dislike the smell in the shower, want every tap treated, or are protecting a home dialysis setup or aquarium supply. Compare the approaches in whole-house filter vs reverse osmosis.

When to call a pro

A non-backwashing tank like the Rhino needs no drain or power, but Aquasana recommends a licensed plumber. A backwashing catalytic tank needs a drain, an outlet and enough flow to backwash (4 to 10 gpm depending on size, per US Water Systems). Call a plumber if you do not have those near your main line. For home dialysis, involve your dialysis provider before changing anything.

Which products fit

If your report says chloramine and you want the whole house covered, catalytic carbon is the next step. Neither pick is certified for chloramine, so read the numbers.

No drain or power needed: Aquasana Rhino Chloramines

Both tanks are catalytic carbon. Aquasana’s own data sheet shows an 83% average chloramine reduction, falling to 68.7% to 75.5% over the last 400,000 gallons of the 1,000,000-gallon rating, so expect some chloramine to get through late in the tank’s life. More in our Aquasana Rhino review.

Backwashing, sized by flow: US Water Systems Matrixx catalytic carbon

It comes in 5 to 20 gpm sizes with published media volumes, so you can check contact time yourself. It needs a drain and power, and US Water Systems lists backwashing filters as non-returnable under its commercial policy, so confirm residential terms first. See our US Water Systems Matrixx review and the best filters for city water.

Questions people ask

Sources

1. CDC: About water disinfection with chlorine and chloramine
2. EPA: Chloramines in drinking water
3. EPA: Basic information about chloramines (2009)
4. EPA: Can chloraminated or chlorinated water be used for dialysis or in an aquarium? (2009)
5. EPA: Consumer Confidence Report information for consumers
6. Pennsylvania DEP: Chloramine in drinking water
7. Illinois American Water: Chloramination FAQs
8. WC&P: Chlorine and chloramine removal with activated carbon (Robert Potwora, 2009)
9. WC&P: Activated carbon, filtration, contactor or both (Gary Battenberg, 2018)
10. WC&P: Chloramine reduction under NSF/ANSI 42 (Rick Andrew, 2011)
11. NSF: NSF/ANSI 177 shower filter certification
12. Taylor Technologies: How DPD tests for free and combined chlorine
13. Fritz Aquatics: About chloramine
14. EPA: National primary drinking water regulations (disinfectant limits)
15. Aquasana Rhino Chloramines product page
16. Aquasana WH-1011 performance data sheet
17. US Water Systems Matrixx catalytic carbon product page
18. US Water Systems Matrixx catalytic carbon spec sheet
19. SpringWell CF1 product page