Recent research has shown that many common toilet cleaning products can damage the rubber flapper causing significant leakage. Dropping certain toilet bowl cleaners (usually in the form of large white tablets) into your toilet tank may result in damage to the parts within the tank, especially if you do not flush your toilet at least once a day. Some manufacturers may even void the warranty on those parts. If you chose to use these cleaners, the toilet must be flushed at least once per day. As an alternative, use the in-bowl toilet cleaner rather than the in-tank cleaners.