If a tap drips into a 5 litre container how long does it take to fill. answer it depends on the size of the drip its got some thing to do with volume.Ours usually lasts 48 hours - two adults and two young children using it almost all of the time.
A word of caution though relating to a previous post - it is not advisable to travel with water in the flush tank or the hot water tank (in a caravan). It's not a matter of weight but one of stability. Water sloshing about is not good for a stable tow, and people such as the Caravan Club advise against this.
Good luck!
Merry Xmas