... preservation hours72 hoursHailstone resistanceDia=25mmGuarantyWater tank for 5 years, tube and frame for 15 years1,vacuum tube length:47/1500mm,58/1800. ... /3000w7,frame material :202 stainless steel8,we could product for customer'special needIt has 15years long life span ,and ... ,the tap water flow in the tank ,if the water is full,it will close the valve automatically vacuum tube solar water heater