Here are some notes from the manual:
1. When picking up small amounts of liquid the filter may be left in place,
2. When picking up large amounts of liquid we recommend that the filter be removed. If the filter is not removed it will become saturated and misting may appear in the exhaust.
Warning: do not remove the filter cage and float. The float prevents liquid from entering the impeller and damaging the motor. The cage prevents fingers from touching the impeller.
3. When the liquid in the drum reaches a predetermined level, the float mechanism will rise automatically to cut off airflow. You will know that the float has risen because vac airflow ceases and the motor noise will become higher in pitch, due to increased motor speed. When this happens, turn off the vac unplug the power cord, and empty the drum.
4. After using the vac to pick up liquids, the filter must be dried to avoid possible mildew and damage to the filter.