According to the Department of Public Works:
Wastes generated from pool, spa and fountain cleaning are among the many common storm water pollutants that can degrade water quality. Routine pool maintenance activities generate a variety of wastes. Chlorinated pool water, backwash residues, algicides, and acid washes are a few examples. It is illegal to dispose of these wastes to the storm drain system! Pool drain water may be disposed to the storm drain system only if the chlorine is below 1 part per million and only if the water contains no other contaminants such as backwash residues or algicides. Chlorine, bromine, and algicides can kill aquatic life!!!
San Diego county has a huge stretch of coastline harboring aquatic life that can and will be affected by contaminants from pool water. Help us, help you, save the environment!