Check the listing for details. Duda Solar Water Heater Tanks - Choose Size & Number of Coils. Color: ‎Single Coil, Condition: New. Listed at 1076.72 USD. Stainless Steel Solar Water Tanks Active solar water heaters utilize an antifreeze as the working fluid in the system. This fluid carries the heat collector from the sun to a tank stored in a different location. In order to exchange heat to the water within the tank, a heat exchanger is required. Our solar water tanks come with a built-in copper heat exchanger, so the working fluid can simply pass through the coil, thus heating the water inside. Stainless Steel Tanks Are Better than Vitreous Enamel Tanks Our tanks are made of food grade stainless steel layered with a galvanized steel shell on the outside for increased strength against high pressures. Stainless steel is superior in solar water heating applications because it can handle the very high temperatures produced by solar water heaters, has excellent corrosion resistance and can handle the constant high pressure resulting from constant heating throughout the day. Vitreous enamel tanks are made of carbon steel and utilize a glass lining to protect the steel from corrosion. Unfortunately, these cheaper style tanks cannot handle the constant pressure in solar water heater systems. When the water temperature rises to 70°C or greater, which is typical for a solar water heater system, there is high risk of cracking of the glass lining due to excessive expansion and sticking to the carbon steel. Once cracks have formed, the carbon steel may rapidly corrode due to exposure to the water, which often results in premature failure. Copper Heat Exchange Coils Every tank comes with a copper coil in the bottom of the tank for heating by the solar loop. The coil extends from where the ports enter and down to the bottom of the tank so that the entire tank of water can be heated fully by the solar loop. Dual coil tanks come with a 2nd coil installed on the top. The top coil can be used for other heat applications. Inner Tank: Food Grade SUS 304-2B, Outer Tank: Galvanized Steel 0.5 mm thickness Insulation: high pressure automatic polyurethane foaming layer, Density of 36 kg/m3, R-Value: 12.5 In Tank Coil: TU1 copper (Red Copper), thickness: 1mm, Length of Coil:66 ft Water Ports: 3/4" NPT, Coil Ports: 1/2" MPT, T/P Valve/Abode Rod/Drain Port: 3/4",