My company just bought less than a month, furthermore we got not much staff using it and the water tank is always full.. :err:Catty, to my knowledge, when the cold water run out in the water tank, it will refill from the container and it take about 20 mins for the water to become cold.
Further more, it is recommend to change the filter every 3 months for home usage and if your is consume at your office area with lotsa of drinkers, filter should change more often.
When did your filter last change?