How often do I need to drain the watertank? Jessica 29 June 2021 00:53 Updated We recommend draining your water tank before it reaches the line in the tank, as this may cause your AC to shut down. Related articles What size is the window kit? Why is the window kit heat exhaust hose so short? Can I buy a longer one? Will my AC unit cool my whole house? What size Air Conditioner shall I get?