Unlike other water tank bidets, the COCO bidet uses continuous water heating technology. What this means is that with a normal tank it does not start to heat the water until after all of the water is used. The COCO bidet starts to reheat the water supply once it starts to be used. That is how we can have such a low profile tank. Our tank is 800ml vs competitors 1L but we still provide more warm water. Also it heats the water much more quickly than most bidets.