Chloramine
NH₂Cl·Affects skin,, lungs
Chlorine combined with ammonia. Used by roughly one in five US utilities because it lasts longer in distribution pipes than free chlorine.
NH₂Cl
EPA limit
4.0 mg/L (MRDL)
Most at risk
People with sensitive skin, asthmatics, kidney dialysis patients, fish/reptile owners
Found in
City water
AquaOx filters
YesCentaur catalytic carbon
What it does to you
Health effects
Chloramine is regulated under the same 4.0 mg/L MRDL as free chlorine and is similarly considered safe to drink at municipal levels. The chronic concerns mirror chlorine's: dermal irritation, eczema flares, worsened asthma symptoms, and a persistent chemical smell in steamy bathrooms.
Two populations need to take chloramine seriously beyond the general advice. Kidney-dialysis patients must have chloramine removed before water enters the dialysis machine, since the membrane lets it pass directly into the bloodstream where it damages red blood cells. Fish and amphibian owners must remove it from tanks, because unlike free chlorine it does not off-gas overnight.
Chloramine forms its own family of byproducts called nitrosamines (notably NDMA), which the EPA classifies as probable human carcinogens. The reaction chemistry is different from chlorine's, so utilities that switch to chloramine often see THMs drop and nitrogen-based byproducts rise.
Where it comes from
How it gets into your water
Chloramine is made by mixing chlorine with ammonia at the treatment plant. The resulting compound is a weaker disinfectant than free chlorine but it persists much longer in distribution pipes, which is why utilities serving long networks or hot climates favor it.
Once it leaves the plant, chloramine maintains a residual all the way to your tap. Unlike chlorine, it doesn't evaporate from an open glass on the counter or boil off easily. Removing it requires either catalytic carbon, vitamin C, or extended boiling.
Municipal treatment plants
Chlorine plus ammonia for longer-lasting residual
Distribution residual
Persists end-to-end in the network
Hot showers
Releases chlorine and ammonia vapors
Tap water
Direct ingestion
Find out for yourself
Is it in your water?
Roughly one in five US municipal systems use chloramine instead of, or in addition to, free chlorine. You can check by reading your utility's annual Consumer Confidence Report (CCR), which lists the disinfectant in use. Major chloraminated systems include Washington DC, San Francisco, Tampa, and Philadelphia.
Levels are typically held in the 1.5 to 3.5 mg/L range and don't fluctuate as sharply by season as free chlorine does, because chloramine is more stable.
The fix
How AquaOx filters it
Chloramine is harder to filter than chlorine. Standard activated carbon strips chlorine readily but is much slower with chloramine. Catalytic carbon, which is the core media in AquaOx systems, is engineered specifically for this reaction and reduces chloramine to non-detect levels at residential flow rates.
Because AquaOx is whole-house, chloramine is filtered before water reaches your shower, dishwasher, ice maker, or fish tank. That matters: chloramine off-gassing from showers is the most-reported sensitivity complaint in chloraminated cities.