This article breaks down the proper way to drain your Plunge unit with and without a drain hose. 

1. Make sure the power is off and the unit is unplugged.

2. On the back (long side) of the unit, locate the drain valve. 

3. If The Plunge is located outside and in a place that can get wet, you can open the valve and just let the water out. If The Plunge is in a location that cannot get wet, you have the option to attach a garden hose and drain where ever you'd like.