There is free filtered water on my floor available from a 5-gallon water dispenser unit. The replacement water bottles are about 30 feet away in a storage room. As it would happen, I tend to find the water fountain completely empty more often than I would like.
In the perfect world, the person who takes the last of the water would go and fetch a new cartridge, or if the person does not have the strength then he or she would ask someone else to do so.
What should I do? Put up a poster saying "Thank you for drinking from this fountain. Are you doing your part in making sure we can all enjoy to drink as well?"