After reading that a black slime/gunk builds up I cleaned both the hose and the 90 degree elbow at the rear of the unit which connects to the hose. After a while the hose drainage would again stop working and the bucket would fill up. My next solution was to buy kids craft pipe cleaner, twist 2-3 together to form a single pipe cleaner, and feed it into the back of the 90 degree elbow and as far in the back of the unit as I could. I found another black gunk buildup in there. Since I did that about 3 weeks ago I haven’t had any problems but can assume the gunk will build up again and I will have to repeat the process.