Drink when thirsty or on a set schedule?

From what I've been reading, this is a hotly debated topic.
As a retired Math Teacher, drinking water on a schedule appeals to me better than drinking water only when thirsty (too haphazard).
I'm proposing drinking 16-ounces at 8am, noon, 4pm, and 8pm....12-hours drinking water....12-hours Dry Fasting. The total amount of water can be adjusted. For example...if not thirsty at 8am, the next 16-ounce drink would be noon. If not thirsty at noon, the next 16-ounce drink would be 4pm, etc. Drinking water at other times is not allowed. For me, the 16-ounce figure works best for a proper 'flush'. It depends on the persons Body Size. Small people may do best on 8 or 12-ounces....large people on 24-ounces, or more. Any comments?.....WY