There is a condensate trap inside the furnace. Check the drain line from the furnace first. Trap may need to be removed and flushed with hot water and bleach. Difficult to remove and easy to damage on those units so you may want to call a Pro.
"Cut it twice and it is still too short". To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
The Following User Says Thank You to yuri For This Useful Post: