This toilet tank bank is designed to be filled with water and inserted into your toilet cistern. When the toilet is flushed, the cistern never empties fully, thus saving water as less water travels back into the cistern after flushing. Ideal for older cisterns which can have a flush level of between 9 and 12 litres, this toilet tank bank is made from non-corrosive materials that resist microbes and fungal growth. One toilet tank bank can take up to 2 litres of water and it has an airlock fill valve, so no water ever evaporates and you never have to refill the bank, making it a maintenance-free product. The product also includes a clip for attaching to the side wall of the cistern, so it fits neatly in place and won't float around or get caught in the toilet mechanisms. To use, fill with water and close the cap, open the cistern cover, flush the toilet, place the toilet tank bank in position, clipping it onto the side wall of the cistern, ensuring it won't interfere with the ballcock or other mechanisms. Replace the cistern cover and start saving water.