Somewhere I read or heard the drain valves on the fresh-water tanks are the same model as the dump valves on the black and grey waste tanks. If that's so, then they will have a similar life expectancy from the manufacturer, i.e., about 7 to 8 years. But, given our fresh-water tanks are not drained often and therefore the drain valves are seldom used, perhaps we could realistically expect a bit longer life.