On arrival I found upstairs drain line backed up. Also found condensation inside the emergency drain pan. Removed water from pan. Flushed and treated drain line and primary pan with drain treatment. Did inform homeowner that the outside drain line extension into the yard needs to be upsized since there are two systems feeding into one three-quarter inch pipe as this is contributing to the blockage issue. Also recommend installing a ceiling saver water safety switch into the upstairs unit. The secondary port was never plugged and when the primary line becomes backed up, condensation will flow into emergency pan.