Copper sulfate was commonly dumped directly into pools in the early to mid 1900s as an algae killer and disinfectant. There is a vintage paper on it in industrial & engineering Chemistry titled "The Use of Copper Sulfate in the Purification of Swimming Polls" It releases copper ions that disrupt algae enzymes. People reported "healing" from aches and pains and other wonderful side effects. The paint, pipes and ladders used to be made from copper also. Copper is wonderful for purification of water and the body's chemistry. When CPVC became popular in the late 80s early 90s, it was more cost effective, didnt corrode and didnt need soldering. Part of me believes there was ulterior motive...