If the water separator is full, your air compressor won’t benefit from a clean air stream anymore. One of the significant problems with full water separators is not getting proper compressor airflow. This means you can’t use your compressor at its full capacity.
Your air tools will likely corrode as water sips through their mechanisms, significantly reducing their lifespan and utility. That will cause you to waste money having to buy new tools.
Full water separators can cause your compressor to work more, increasing your electricity bill and overheating the unit.