The powerful oxidants chlorine and chloride occur naturally in groundwater and deep aquifers, and concentration levels as low as 250 mg per liter -- the maximum the Environmental Protection Agency recommends for safe consumption -- can cause water to have the distinct, sharp chlorine smell and taste.
Chlorine is usually used to disinfect water from bacteria and other organisms. It can be added to municipal water supplies and leech through the groundwater into private wells or may be leftover from a previous disinfection of the well by shock chlorination, in which chlorine bleach is added to well water and then flushed. It is the most recommended and usually the safest way to treat infestations in wells or to prevent contamination after construction or maintenance around the well. However, wells and pipes must be thoroughly flushed after a shock chlorination to rinse away excess chlorine.
Sodium and Chloride
Sodium and chloride may also contaminate private wells and cause a chlorine-like odor or taste. Sodium and chloride enter wells through groundwater that has come into contact with road salt, sewage, fertilizers and some types of water softeners. High levels of sodium and chloride are corrosive to pipes and can cause damage. They can also cause intense intestinal discomfort in humans and animals or be fatal to plants and crops.
Determine if your well water contains dangerous levels of chlorine, chloride and sodium. Professional water testers can come and perform tests on water, you can send samples of your water to labs or use home testing kits. If you do have excessive concentrations of these or other chemicals, you must identify and fix the source of the contamination before completely flushing your well and plumbing.