Arrived on site. Checked in with management. Obtained roof access. Inspected both RTU units. Found RTU#2 drain pan overflowing. Found RTU#2 condensate drain line backed up. Disconnected drain line from system to allow drain pan to drain out onto roof top. Left condensate drain line disconnected at this time. Found drain line with an upwards slope making drainage to flow improperly. Recommend clearing drain line and remounting with a downwards slope to allow proper water flow.