Why are Chlorine Used in Water?

Chloramines are used to disinfect tap water because of their remarkably long-lasting disinfection properties. Celebrated for their strength as a “secondary disinfectant”, chloramines remain in the water much longer than chlorine. Chloramines are a very stable compound, and won’t readily dissipate or lose potency. Though a weaker disinfectant than chlorine, they retain their disinfection characteristics much longer than chlorine. This means even if you are the home all the way at the outskirts of the city and at the end of the water main, your water will still come out of your tap disinfected and full of chloramine.
Chlorine does have several downsides. Chlorine is a very volatile compound and is eager to dissipate from the water supply. EPA standards require that there is a residual 0.5ppm of the disinfection agent in the water. Since chloramines are so stable, this is easily achieved. Chlorine, however, is far more likely to gas off and leave the water before that house at the end of the municipal supplier. Additionally, when chlorine is added to a water source with organic matter (like a lake or river) it creates “disinfection byproducts” (or “DBPs”.) One of these, trihalomethane (or THM) is a volatile organic compound with several significant health implications. Prolonged consumption of THMs is linked to reproductive complications and cancer. While municipal treatment plants work diligently to ensure that the DBP levels remain low in their water, chloramines offer a safer alternative in this regard. They do not create any byproducts when combined with organic matter.