why does my dryer keep stopping?Hotpoint Ultima CTD85?

We installed the dryer two years ago using the hose on the reverse so that it was vented to go outside and not have to use the reservior drawer that needs emptying regularly. Now the display is flashing 'empty water'. We have taken the dryer out and checked the hose and the outlet and there is no blockages and no restrictions. The hose has no kinks in it that might restrict the air.