Chloramine is a chemical compound formed when chlorine and ammonia are combined, primarily used as a disinfectant in water treatment. Its widespread adoption stems from its effectiveness in killing disease-causing microorganisms, ensuring water remains safe for consumption.
The Distinctive Scent of Chloramine
The scent associated with chloramine is often described as a “bleach-like,” “chemical,” or “swimming pool” smell. While many people attribute this odor to chlorine, chloramines are actually responsible for the noticeable scent. The presence of ammonia within the chloramine compound gives it a distinct profile compared to pure chlorine, often perceived as less sharp or volatile. This characteristic odor can also be described as a “musty” or “swampy” smell, particularly if contaminants are more advanced.
The intensity of this scent varies depending on its concentration. For instance, the average person can detect monochloramine, a common form, at concentrations around 3 milligrams per liter (mg/L).
Common Sources of Chloramine Odor
Chloramine is widely prevalent in municipal tap water systems across North America. Many water treatment facilities opt for chloramine due to its stability and prolonged disinfectant properties, allowing it to maintain residual disinfection throughout extensive distribution systems. Approximately one-third of public water systems in the United States utilize chloramine for residual disinfection, serving over 68 million people.
Swimming pools represent another common environment where chloramine odors are frequently encountered. In pools, this smell typically originates from “combined chloramines,” which form when chlorine reacts with organic matter introduced by swimmers. Substances like sweat, oils, cosmetics, and urine contain nitrogen and ammonia, which readily combine with free chlorine to create these compounds. Therefore, the strong “chlorine” smell in pools is not from free chlorine, but rather from these combined chloramines.
Understanding a Strong Chloramine Smell
A faint chloramine smell in tap water is generally normal and indicates that the water is being properly disinfected. However, a more pronounced or persistent odor can suggest specific conditions within the water system. In municipal water, an intensified smell might occur during routine system maintenance, such as flushing or “shocking” water lines, which temporarily increases disinfectant levels. It could also point to issues within household plumbing, like the accumulation of organic material in aerator screens or stagnant water in pipes.
In swimming pools, a strong chloramine smell is a clear indicator of accumulating combined chloramines. These combined chloramines are significantly less effective as disinfectants than free chlorine, being 60 to 80 times less potent. Their presence signals that the free chlorine is reacting with contaminants from swimmers, and a strong smell often means there is an excess of these byproducts. This accumulation is a sign that the pool water needs additional treatment to break down these compounds and restore proper disinfection levels.