...with an added cost of some 10-15 US$ for a steel tank that being just over something generating hot, humid air all the time will rust in no time or 40-60 US$ in the case of stainless steel.
Then everyone has 20 Kg of sand at home (if you have to transport the 20 Kg of sand all the theoretical transport savings are gone).
...but most people, whether using an installer or not, don't have multiple faucets that can dispense sand. Nearly everyone _does_ have access to water though.
Then everyone has 20 Kg of sand at home (if you have to transport the 20 Kg of sand all the theoretical transport savings are gone).