It takes a long time for the hot water from the tankless unit to reach the dishwasher, consequently, the dishwasher isn't getting the dishes clean. Can I put a mini tankless unit in line and under the sink to 'preheat' the hot water going to the dishwasher? Or maybe just use the mini unit on the cold water line to just supply the dishwasher? Also, I'm replacing old copper pipe with PEX. Do I need to insulate it?