Don't worry about the weight of the water bottles. All that really matters is how much weight you lost. A pound = a pint is pretty close.

I usually do about one 24 oz water bottle per hour if it's warm and humid. More if it's hot. I once did a double century ride which reach 95 F degrees and I drank gallons of fluids.

One thing that does help is sports drinks. The amount of sodium and other electrolytes in them help use the water quicker. Plus the sugar is a good source of fuel. Also drinking a lot of plain water can be dangerous as it can cause water intoxication (AKA Hyponatremia) which can be dangerous and even deadly The electrolytes in sports drinks help prevent this condition.