Seriously though, for an otherwise healthy adult person with normal renal function to suffer from hyponatremia from water overdose, it takes a water intake of somewhere close to 20 litres of water per day, a feat most would balk at. Equally unlikely as a cause of hyponatremia in most Americans is hyponatremia secondary to a dietary deficiency of sodium as the average Western diet nowadays contains far more than the daily requirement of sodium.
This leaves sodium losses and SIADH as the most common causes of hyponatremia. The treatment for hyponatremia is to find and treat the underlying cause and to consider fluid restrictions until the hyponatremia is corrected.