Normal, healthy (physically, nutritionally and mentally) individuals have little reason to worry about accidentally consuming too much water. Nearly all deaths related to water intoxication in normal individuals have resulted either from water drinking contests, in which individuals attempt to consume large amounts of water, or long bouts of intensive exercise during which electrolytes are not properly replenished, yet excessive amounts of fluid are still consumed.
Water can be considered a poison when over-consumed just like any other substance. The recommendation from the medical field is to drink at least 1 - 2 liters per day depending upon body mass. Water intoxication would only occur at levels far higher than that.