Unlike other water dispensers or ceramic water dispensers' "open space" designs, which allow air, dust and bugs to pollute the water, after opening the bottled water, you can just lift the dispenser support and screw it into the bottleneck of bottled water tightly. When I said tightly, it is because the bottleneck on the water dispenser is made of silicon, which is capable of attaching to the bottled water tightly without letting any air through. When no air and no humidity escape the bottled water, the water stays clean forever.