Furnace hot water tank
How often should a furnace be cleaned?
Should I replace my water heater before it fails?
How long do instant gas hot water systems last?
Taking into consideration the above information, you can expect your hot water tank to last, on average, for about 7 to 15 years. However, if you go for a tank-less (or instant) hot water system, you can expect to add at least a few years onto that.