I would strongly recommend that you take at least 2 x 750ml water bottles (preferably 900ml [1000ml are available but don’t fit in a bottle cage very well]).
In ‘normal’ cycling conditions you will need to drink about 500ml (roughly a pint) of liquid every hour. You can double that if it is hot and/or you are working hard. You might feel you can get away with less but you will suffer for it on a long trip (see section on hydration).
So if it is hot, your 2 x 900ml bottles will last you about 2 hours. If you were carrying only 500ml bottles you would need to fill up every hour.
Whilst you might be happy to stop every hour there may be sections of the trip where it may take you longer than that to get between watering points, depending on the route you have selected. So make sure you are carrying a reasonable supply of liquids.
- Carry two bottles of at least 750ml capacity to avoid having to stop too often for top ups, especially in hot weather.