That's impressive, but not uncommon for older water heaters. The older water heaters purchased in the 70's and 80's had much thicker steel and more porcelain than today's units.
- Manufacturers have cut so many costs from the manufacturing process, most steel water heaters made today will not last much longer than their warranty of 5 or 6 years.
- It's much like the automobile, the thickness of the metal on today's units is very thin compared to older models and therefore they tend to rust out and leak over time.