Upon arrival found that the main drain line was clogged up and over flowing out of drain vent. With approval blew drain line out and extended vents so water wouldn’t overflow out of drain. After blowing out drain, sink in bathroom clogged up. Took apart p-trap and found it clogged with gunk and hair. Cleaned trap and put trap back together. System is now draining properly at this time. Recommended a plumber due to drain could still have hair and stuff clogged up in it.