The current guarantee period for all Ariston unvented cylinders featuring the ProTech anti-corrosion system is 10 years on the tank and 2 years on electrical components. The current guarantee period for all Ariston unvented cylinders featuring a sacrificial magnesium anode (anti-corrosion system) is 5 years on the tank and 2 years on electrical components. On older Ariston unvented cylinders models (pre march 2001) the guarantee periods are as follows: 3 years on the tank and 1 year on electrical components for Contact models and 5 years on the tank and 1 year on electrical components for Wall Hung, Super Bravo and Comfort models.