Chlorine Pool Chemicals

Chlorine Disinfectants

The options for selecting the form of chlorine disinfectant to use in pools are quite varied, and the choices are complex. Table 14.3 gives the properties of each form. Gas chlorine costs the least, and the relative cost of each form of chlorine increases as you move right across the table. The cost of the disinfectant tends to be less the higher the concentration of available chlorine. The safety issues are more complex than they might appear. The hazards of gas chlorine are well known. The solid forms of chlorine, such as calcium hypochlorite, are quite reactive. When exposed to organic compounds, they can generate a great deal of heat and are potentially explosive. Because solid chlorine seems inert to the untrained worker, it is often stored beside motor oil or gasoline or left in areas where moisture can start a chemical reaction. Even a pencil with a graphite core that drops from a shirt pocket into a container of calcium hypochlorite could result in a chemical reaction leading to a fire that would release free chlorine gas [7].

The following chemical reactions produce chlorine by-products that reduce the effectiveness of chlorine and cause most eye irritation.

• Cl2 + H2O = HCl + HOCl
  Chlorine + Water = Hydrochloric Acid + Hypochlorous Acid
• HOCl + NH3 = H2O + NH2Cl
  Hypochlorous Acid + Ammonia = Water + Monochloramine
• HOCl + NH2Cl = H2O + NHCl2
  Hypochlorous Acid + Monochloramine = Water + Dichloramine
• HOCl + NHCl2 = H2O + NCl3
  Hypochlorous Acid + Dichloramine = Water + Nitrogen Trichloride