Water heater maintenance is easy to overlook because the tank just sits there and has no moving parts to worry about. But inside, two things are constantly attacking your water heater: sediment and rust.
Most steel water heater tanks are lined with glass to prevent rust. But the glass lining is never perfect, and the constant temperature fluctuations cause it to expand and contract, causing very small openings. When water eventually penetrates the lining, the tank begins to rust. The good news is, there are ways to minimize the damage.