I had to leave my property for two weeks. I was concerned about the pool and debris getting caught in it, so I decided to disable the water pump. After all, there would be nobody there to empty the skimmer and clean it out. The guy who cleans my pool three times a week had mentioned to me that I should buy some chlorine tablets to help keep the water clean especially when the pool won’t be in use for a while. Before I left, I added six of them to various spots of the pool and left. I came back home two weeks later only to find these brown stains right where I had dropped the tablets. Immediately, I called a pool expert recommended by a friend. He told me that my pool cleaner gave me bad advice and that I should never use chlorine tablets in my pool. He said that they can be extremely acidic and damage the lining of my pool. He extracted the tablets from the water with a net and cleaned out my pool for me.