I'm replacing my 8 year old unpressurized storage with a pressurized tank. In the old system I preheated the dhw with a hx in the tank. How can I preheat the dhw using a pressurized tank? My boiler and storage are in the workshop 100 feet from the buildings they heat. So it is a one way insulated pipe to each building's hot water tank. Really have appreciated the info on this site over the years!