Into hot water again. Yes, the luxury of having on-demand hot water in The Tortuga Expedition Camper was addictive. Our Seaward marine hot water heater took heat from the engine coolant or our Espar D5 Hydronic coolant heater. The problem was, we were carrying around 6 gallons of water that could not be used unless we pumped cold water into the tank to push the hot water out. The solution was to install a FlatPlate double wall brazed plate heat exchanger. This little piece of 21st-century technology, about the size of a loaf of bread, will give us endless hot water as long as the engine or the Espar D5 Hydronic is pumping coolant through its plates. The diesel-powered Espar D5 is even smaller than the FlatPlate, and can also preheat the engine on cold mornings, thanks to a system of valves and distribution manifolds designed for us by Espar. More on this after we’ve taken a hot shower.