I have a few brown stains in my pool. They look like comets or something. They are 4 to 6 inches across and taper down to nothing and are about a foot long. A friend looked at them and said that he had similar stains and he hired a man who put pvc pipe into the pool over the stains and then poured muriatic acid down the pipe and that it removed the stains on the bottom of his pool. Does this make sense?