I recently visited two neighboring plaster swimming pools that had been treated for several years by a gas-shooter, applying chlorine gas directly into the pool. One of the owners said the gas-shooter would also add soda ash at the same time to offset the low pH of the chlorine gas. He also said that both pools were recently treated with ascorbic acid to remove very dark gray staining. Apparently the chlorine was quite high after the gas shooter would leave each week. Although the owner did not test the water, he said his wife would sit in an innertube-shaped float in the pool, and her swimming suit was distinctly bleached below the water line.
The underwater portion of the stainless steel pool ladders, and the stainless steel underwater light rims are very darkly charcoal-colored. What is the likely water chemistry that was happening that discolored the stainless steel and what was happening that caused the dark gray staining of the pool plaster surfaces?
Thank you.