I have a flue that is around 14' tall. Bottom 5' is single wall black pipe to ceiling. From ceiling to top is class A simpson duravent. I bought and installed their through ceiling kit, this was put in about 2 years ago. This is my problem, I have a 6" brush and clean it myself. From the start it has always been hard to get the brush past the transition point of the two different types of pipe. A couple weeks ago I went up to clean flue and could not get the brush past that point at all, seems like it is getting hung up on the side of the flue. I know I used the right pieces supplied with the kit. Has anyone else experienced this with their install?