The decision to use stainless steel for the manufacture of the "Tank in Tank" was made in the 60's. It was chosen for its well established reliability and advantages over other materials, namely: Stainless steel is stable at elevated temperatures above 180ºF, which is not the case for tanks manufactured from mild steel protected by a glass lined coating. It is for this reason that some manufacturers include a clause in their guarantee limiting the DHW storage temperatures to 140°F or even 130°F. Stainless steel, as its name suggests, is resistant to corrosion. The protective coatings in an enameled tank can be damaged by a shock during transportation, unloading or maneuvering it into position. This is not the case with stainless steel. Last, but not least, a stainless steel tank does not need a sacrificial anode. This is a major advantage versus conventional water heaters. Stainless steel is also universally recognized for its hygienic properties and is frequently used in the manufacture of items for the food industry and for surgical instruments. There is little chance of its use being questioned on the basis of it being a health hazard. Conversely, protective coatings, i.e. enameling cannot be examined everyday and their failure could lead to unhealthy consequences.
There are two major types of water heaters, those with coils and the twin walled tank. The water heater which we manufacture, the "Tank-in-Tank", doesn't fall within either of these categories. The difference between our water heaters and those with coils is clear since in the former the primary fluid heats the domestic hot water from the outside while the other heats it from the inside out. On the other hand the twin walled water heaters have an area near the bottom which is not heated and the heat transfer surface is smaller than in the "Tank-in-Tank".
The most important characteristic of the "Tank-in-Tank" system is its capability for auto-descaling and its long life expectancy combined with the reduced requirement for regular maintenance.