Hyponatraema is a recognised danger amongst those that take part in marathons and vigorous exercise regimes. Isotonic sports drinks have helped reduced the risk in recent years, but I acknowledge that it still occurs.
Nevertheless, this lady was asking for information here on water intake for dieting purposes. Under these circumstances, the recommended normal intake of water for an adult is very roughly around two litres of water per day and it should be remembered that most of us do not achieve that level of water intake.
There is therefore some scope for most of us to increase our water intake, with the exception of those with oedema, cardiac problems, kidney disease and hypertension. As for excessive water consumption, the human body is well capable of warning us when water intake has become excessively high. The need to rush to the toilet frequently along with high urine output will soon make the lifestyle intolerable. You need only ask someone who's on diuretic treatment to verify this - I can almost guarantee they have had to change their habits.
You also have to remember that sportsmen/sportswomen including marathon runners have only one goal in mind whilst running and when such determination is present, these warning signals from the body are hindered subconciously. The minute they cross the finishing line, they become all too well aware of what has happened to their bodies.
I very much doubt that any of these adverse conditions would arise in a sedentary or normally active dieter as these key criteria will not have been met.