The more limescale that has accumulated, the more descaling solution is needed. If the limescale does not dissolve completely during use, this means that not enough descaling solution has been added and the acid agent has been used up. In this case, simply add a little more descaling solution and let it work again until the limescale is completely dissolved. As our descalers have a very high limescale dissolving power, we recommend a sparing dosage, which should only be increased if necessary.