The average life expectancy of a tank-type water heater is about 10-12 years. You can see if your traditional tank-type is still in working order by assessing the anode rod. This rod protects the interior lining by attracting all corrosive particles to itself through a process called electrolysis.
When the rod corrodes, the tank can no longer do its job correctly. Those corrosive particles will settle at the bottom of the water tank and destroy the lining. Once you notice corrosion building up inside your water tank, you need to start looking for a water heater replacement.