I wouldn't flush CLR...
Can you say for certain that it won't harm rubber, neoprene or flexible PVC, Steve? Or that it can't react negatively with a chemical holding tank treatment?You may not have had any problems using CLR...but can you guarantee that it won't cause problems for anyone? I'm VERY reluctant to recommend the use of any product that carries warnings about inhaling the fumes, wearing rubber gloves, and avoiding contact with metal.