You should not decalcify machines that have heat exchanger boilers. Due to the design of the boiler, it would be nearly impossible to remove all of the decalcifying solution short of removing the boiler from the machine and taking it apart yourself - this is not recommended. The best thing you can do to keep your machine clean is to backflush it. This is a simple process that removes coffee oils and residues from the brew group through the solenoid valve. I have provided a link below to our article on backflushing so that you can learn more. In addition, I have linked to Urnex Cafiza and Backflush discs, both of which are necessary for backflushing.