What Is Chloramine? Why Does My Tap Water Small Like a Pool?

To cut to the chase, chloramine is a water disinfectant. It commonly occurs when ammonia and chlorine are brought together in a disinfection process. Many (but not yet most) public water supply systems use chloramine a secondary disinfectant agent.

How Chloramines Are Used

In scientific terms, chloramines are amines that contain at least one chlorine atom, directly bound to nitrogen (N) atoms.

The use of chloramines as an alternative disinfectant to chlorine — generally to reduce the formation of by-products such as trihalomethanes while taking advantage of greater stability than free chlorine — is a practice of water disinfection applied in many public water supplies (PWSes). The use of chloramines as a secondary disinfectant also means that the systems must maintain a constant concentration throughout the supply network, avoiding complaints of “pool smell” while ensuring proper cleaning at the treatment plant. In this way, the increasingly restrictive requirements of the various regulations can be met.

The use of chloramines (like monochloramine, dichloramine, and trichloramine), as a secondary disinfectant, implies the prior application of the primary or initial disinfectant, which can generally be chlorine itself, ozone, or chlorine dioxide, since, as indicated in this exposure, the lower oxidizing and bactericidal power of chloramines and the concentrations and contact times they require are such that they are inappropriate for use as a primary or principal disinfectant.

Pool or Fish Smell In Tap Water

The cleaning process, known as¬†chloramination, is a popular one used by many United States public water supply systems.¬†While chlorine dissipates quickly when in contact with air, chloramines are stable in water and will remain for longer periods of time. This makes them good for cleaning out water (say, to kill bacteria), but it means “aging” water will not reduce the smell. Boiling and aeration will not remove chloramine very effectively either. Normally chloramine is removed from the water but if some gets through it can be removed with a filter, including activated charcoal, reverse osmosis, and others.

Background Information

The use of chloramines, since the beginning of the 20th century, has contributed to the improvement of the smell and taste of drinking water. Chloramines are formed by the reaction of chlorine (Cl2) and ammonia (NH3). Inorganic chloramines are formed when dissolved chlorine and ammonium react. During this reaction, three different types of chloramines are formed: monochloramines (NH2Cl), dichloramines (NHCl2) and trichloramine (NCl3).

Inorganic chloramines, free chlorine, and organic chloramines are related in their chemical composition and can be quickly transformed from one another. These compounds are not found in isolation. Inorganic chloramines are not persistent but are more persistent than chlorine-free compounds. Research shows that half the life of inorganic chloramines can range from 1 to 23 days, depending on the circumstances.

Chloramines are usually produced by adding ammonium to water containing free chlorine (HOCl or OCl, depending on pH). The ideal pH for this reaction is 8.4, slightly alkaline water. When the reaction occurs, three different types of inorganic chloramines may form depending on the pH value. Trichloramines are typically created when the pH values are 3 or lower. When the pH value is 7 or above this value, the concentration of dichloramines is higher. The amount of chlorine and ammonium in the water also influences the generation of chloramines. The ideal chlorine/ammonium range is 6:1. During chloramine production, this range usually is 3-5.1. When the amount of ammonium is higher, more dichloramines and trichloramines are formed.