PF000561 LeakDETECT Tablets - Reduce water loss by timely diagnosing and fixing a leaky flapper. Simply drop a FDA-certified, non-toxic, non-carcinogenic tablet in the toilet tank and if the toilet turns blue, then it"s time to replace the flapper. Features: -Tablet. -Detect toilet silent leaks. -All ingredients are food grade additives. -Instructions printed on individual tablet package. -Easy to use - non-toxic. -Tablets are certified to nsf standard 60.