Customer had me out because their guest bathroom sink was constantly filling with water. I got there and immediately knew it was the condensate that caused algae to grow and blocked the drain. I took apart the ptrap and it was solid with the algae, I cleaned it all out and ran my small sewer machine down the line and put it all back together. I then ran the water in the sink for over 10 minutes and made sure there is no leaks, and that it is draining good. It is now working properly at this time. I found no further issues at this time.