This depends on the hard water problems you are trying to resolve. From the moment the Integro is installed you will see differences in some areas, such as how soft it feels and the way water interacts with soaps and detergents. If you have descaled existing appliances before installation then you will also immediately see the difference here too as scale build-up will not return. In a badly scaled up water system the Integro will begin to break down the historical build-up straight away. Over the coming months you will see improvements in flow rate, water pressure, reduced energy consumption, etc, as all the old scale build up is removed.