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Water Quality

Chloramine vs. Chlorine: Your Tap Changed

Cuiven Water Lab  ·  November 20, 2025  ·  6 min read

Tap water pouring from a modern kitchen faucet into a glass

For most of a century, American tap water was disinfected with chlorine. Quietly, that changed. Roughly one in three Americans now receives water treated with chloramines instead, including most major cities. If your filter was designed for the old chemistry, it may not be doing what you think.

Why utilities switched

Chlorine works fast and dissipates fast, which is a problem in long distribution systems: by the time water reaches the far end of a city's pipes, protection can fade. Chloramine, formed by combining chlorine with ammonia, is far more stable. It persists all the way to your tap.

Persistence is the point for the utility, and the problem for you. The same stability that keeps chloramine active in pipes makes it harder to remove at home.

The practical differences

The headline for filter shoppers: standard activated carbon removes chlorine quickly, but chloramine reduction demands catalytic carbon and real contact time. A filter that advertises chlorine reduction may say nothing about chloramine, because the two are not the same test.

  • +Chlorine: dissipates in hours, removed by almost any carbon filter, and largely leaves water on its own if you let it sit or boil it.
  • +Chloramine: stable for days, requires catalytic carbon or extended contact time to reduce, and does not meaningfully leave water by sitting or boiling.
  • +Taste and odor: chloramine is subtler but persistent, and it reacts differently with skin and hair in the shower.

How to find out what your utility uses

Your annual water quality report (the consumer confidence report every US utility publishes) lists the disinfectant in use, usually on the first page of regulated contaminants. You can also search your utility's name plus 'water quality report' and find the current PDF in a minute.

If it says chloramines, total chlorine, or monochloramine, you are in chloramine territory, and your filter choice should reflect it.

What this means for your shower and your glass

In the shower, chloramine's stability means every rinse is a full-strength exposure. Monolith XL pairs KDF-55 redox media with a deep catalytic carbon bed specifically because the carbon's contact time, not just its presence, is what reduces chloramines.

For drinking water, the reverse-osmosis membrane in Opus rejects the dissolved disinfectant compounds outright, before the carbon stages polish what remains. Either way, knowing which chemistry your city uses is the first step to filtering it properly.

Monolith XL's catalytic carbon bed is engineered for chloramine reduction, not just chlorine.

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