Question: how to clean an air conditioning drain line?
Answer: Turn off the power to your HVAC unit. ... 
Find your AC drain line. ... 
Push the stiff, thin brush into the end of the drain line. ... 
Attach the end of your wet/dry vacuum to the end of the AC drain line. ... 
After you've run the vacuum for about a minute, remove the wet/dry vac and head indoors. ... 
Locate the vent tee.