We don’t recommend using tank additives, those tablets or discs that can turn your toilet water so blue, it looks like a Smurf is slowly decomposing in your tank. These discs seem like an easy and maintenance-free option, as they’re designed to be dropped into the tank, where they dissolve over time, spreading disinfectant around the toilet bowl with every flush. But according to James Walsh, vice president of product management for toilet manufacturer American Standard, the reality is more complicated. “We do not recommend using in-tank cleaners because they will void your warranty,” he told us during an interview. “They will attack the working tank trim in the tank itself.” Basically, such tablets turn all the standing water in the tank into a caustic liquid, which can warp the rubber components required to keep the flushing mechanisms functioning. Over time this can lead to leaks and occasionally prevent the toilet from flushing entirely.
