AquaTank AquaTank is our range of hot water storage vessels in stainless steel as well as enamelled in a standardised capacity range. Operation pressure for stainless steel calorifiers is 10 bar, as for enamelled calorifiers we offer 7 bar and 10 bar.     SolarTank Primary energy storage vessel suitable for heating water from solar circuits and other renewable energy heating sources like heat pumps and geothermal sources. It needs to be connected in a closed heating loop.