Maintain the toilet hygiene with Harpic! Harpic Flushmatic In-Cistern Toilet Cleaner is a drop-in tank tablet which helps you prevent the build-up of stains giving you a continuous clean toilet. A single block lasts approximately up to a month and makes you experience a fresh Citrus fragrance with every flush. It is safe to be used with septic tanks and all other toilet cleaners. You can replace the block as the green colour of the flushed water starts to fade.