Five gallons would weigh around 42lbs or 19kg because the weight of a gallon of water is 8.3496 lbs. or 3.78 kg, so five gallons would weigh around 42lbs or 19kg. This is just an approximation.
How Much Does 5 Gallons Of Water Weigh
Bottom Line
To summarize how much does 5 gallons of water weigh is about 42 pounds in US customary unit and about 35 pounds in UK customary unit.
Resource: https://en.wikipedia.org/wiki/Gallon
