Customer had me come out on an emergency call that was their upstairs sink was continuously filling up and near overflowing. I got there and found the ac condensates are tied into that sink. I used a small cable to try to clear the algae from inside the pipe but was unsuccessful, I then tried the air snake but was still unsuccessful, my last resort was to go into the attic and cut the vent for the bathroom and run my big sewer machine down to try to clear it, this time I succeeded and I ran the water in the sink for approximately 10 minutes and it was fine. I found no further issues at this time.