Chloramine is a disinfectant that forms when chlorine and ammonia are combined in water. Many Missouri homeowners first hear the word after a water notice, a conversation with a neighbor, or a change in how the tap smells or tastes. This guide explains what chloramine is, why some supply systems use it, and how a household can check its own water.
What chloramine is
Chloramine forms when a water supplier adds ammonia along with chlorine, and the two react to form compounds that remain in the water. It is used as a disinfectant, meaning it is added to limit microbial growth as water travels through distribution pipes. Chloramine lasts longer in water than free chlorine does, which is one reason some suppliers prefer it for long pipe runs.
Why some supply systems use it
A supplier chooses its disinfectant based on source water, pipe age, system size, and treatment goals. Chloramine holds its strength over distance, so it can suit larger service areas. Because the choice belongs to the system, a homeowner cannot tell which disinfectant is in use just by looking at the water. The supplier's records or published water quality reports are the reliable place to confirm it.
Why Missouri homes notice it at the tap
In Missouri, homes on a public supply may receive chloramine in some areas. Homes on private wells usually do not receive chloramine unless the water is connected to a public system or is treated with a disinfectant that is not chloramine. Homeowners tend to notice it for a few common reasons:
- The supplier changed its disinfectant or treatment process, and the taste or smell shifted soon after.
- The home was moved to a different service line, so its water now comes from another part of the system.
- Hot water smells different from cold water, especially when the water heater tank has been sitting.
- Water in a rarely used branch line, such as a guest bathroom, has a stronger or different odor.
- A seasonal change in source water or treatment affects the taste at the kitchen tap.
How to check at home
Free chlorine and total chlorine tests help separate chlorine from chloramine. Chloramine appears in total chlorine readings, but it reads low or not at all on many free chlorine tests. A noticeable gap between the two results can point toward chloramine. Use a test kit made for drinking water, follow the label closely, and record the date and the tap you sampled.
- Confirm the water source. A public supply usually publishes an annual consumer confidence report that states the disinfectant it uses.
- Run cold water at the kitchen tap for several minutes, then fill a clean container for testing.
- Measure free chlorine and total chlorine as separate tests, following the kit instructions.
- Compare the two results. A clear difference between total and free readings suggests chloramine may be present.
- Repeat the check at the hot tap and at a rarely used tap to see whether the results change.
- If the results are unclear, send a sample to a certified drinking water laboratory for a formal report.
Filtering and next steps
Carbon filters that work well for chlorine may remove chloramine less reliably, because chloramine is more resistant to the same process. Look for performance data that specifically lists chloramine reduction, and check that the claim matches the flow rate and use you expect. Before buying any equipment, ask the supplier which disinfectant it uses and whether a change is planned.
For a private well in Missouri, chloramine is not normally expected. A chlorine-like smell from a well is more often linked to shock treatment or a disinfectant feeder that is still in service. Review the well's treatment records, and consider a bacteriological test before assuming the source of the odor. Any test result should be read with the laboratory's report, not with a home strip alone.